Technical Handbook for

Radio Monitoring HF

Edition 2013

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Dipl.- Ing. Roland Proesch

Technical Handbook for

Radio Monitoring HF

Edition 2013

Description of modulation techniques and waveforms with 259 signals, 448 pictures and 134 tables

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© 2013 Dipl.- Ing. Roland Proesch Email: roland@proesch.net Production and publishing: Books on Demand GmbH, Norderstedt, Germany Cover design: Anne Proesch Printed in Germany Web page: www.frequencymanager.de ISBN 9783732241422

Bibliografische Information der Deutschen Nationalbibliothek Die Deutsche Nationalbibliothek verzeichnet diese Publikation in der Deutschen Nationalbibliografie; detaillierte bibliografische Daten sind im Internet über http://dnb.d-nb.de abrufbar.

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Acknowledgement: Thanks for those persons who have supported me in the preparation of this book: Aikaterini Daskalaki-Proesch Horst Diesperger Luca Barbi Dr. Andreas Schwolen-Backes Vaino Lehtoranta Mike Chase Disclaimer: The information in this book have been collected over years. The main problem is that there are not many open sources to get information about this sensitive field. Although I tried to verify these information from different sources it may be that there are mistakes. Please do not hesitate to contact me if you discover any wrong description.

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Content

1  LIST OF PICTURES 19 

2  LIST OF TABLES 29 

3  REMOVED SIGNALS 33 

4  GENERAL 35 

5  DESCRIPTION OF WAVEFORMS 37 

1.1  Analogue Waveforms 37 Amplitude Modulation (AM) 37 

Double Sideband reduced Carrier (DSB-RC) 38 Double Sideband suppressed Carrier (DSB-SC) 38 Single Sideband full Carrier 39 Single Sideband reduced Carrier (SSB-RC) 40 Single Sideband suppressed Carrier (SSB-SC) 40 Single Sideband Modulation (SSB) 40 Independent Sideband Modulation (ISB) 41 Vestigial Sideband Modulation (VSB) 42 

Frequency Modulation (FM) 42 Wide Frequency Modulation (WFM) 43 

Pre-emphasis and de-emphasis 45 

1.2  Digital Waveforms 46 Amplitude Shift Keying (ASK) 46 On-Off-Keying (OOK) 46 Frequency Shift Keying (FSK) 47 

Continuous Phase Frequency Shift Keying (CPFSK) 48 Double Frequency Shift Keying (DFSK) 49 Constant Envelope 4-Level Frequency Modulation (C4FM) 49 Minimum Shift Keying (MSK) 50 Tamed Frequency modulation (TFM) 51 Gaussian Minimum Shift Keying (GMSK) 51 Multi Frequency Shift Keying (MFSK) 52 

Phase Shift Keying (PSK) 53 Binary Phase Shift Keying (BPSK) 53 Quadrature Phase Shift Keying (QPSK) 55 Offset Quadrature Phase Shift Keying (OQPSK) 57 Staggered Quadrature Phase Shift Keying (SQPSK) 57 Compatible Differential Offset Quadrature Phase Shift Keying (CQPSK) 57 Coherent Phase Shift Keying (CPSK) 58 Differential Coherent Phase Shift Keying (DCPSK) 58 8PSK Modulation 58 

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Differential Phase Shift Keying (DPSK) 59 Differential Binary Phase Shift Keying (DBPSK) 59 Differential Quadrature Phase Shift Keying (DQPSK) 59 Differential 8 Phase Shift Keying (D8PSK) 59 

Quadrature Amplitude Modulation (QAM) 60 Orthogonal Frequency Division Multiplexing (OFDM) 62 

Spread Spectrum (SS) 63 Direct Sequence Spread Spectrum (DSSS) 63 Frequency Hopping Spread Spectrum (FHSS) 64 

Incremental Frequency Keying (IFK) 64 Analogue Pulse Modulation 65 

Pulse Amplitude Modulation (PAM) 65 Pulse Width Modulation (PWM) 65 Pulse Position Modulation (PPM) 65 

Digital Pulse Modulation 66 Pulse Code Modulation (PCM) 66 Delta Modulation 67 

1.3  Description of modulation states 68 Asynchronous Data Transmission 68 Synchronous Data Transmission 68 Simplex 69 Duplex 69 Half duplex 69 Semi duplex 69 

1.4  Baud Rate, Bit Rate, Symbol Rate 70 Bit rate 70 Symbol rate 70 Baud rate 70 

1.5  Data formats 71 NRZ (Non Return to Zero) 72 NRZ (S) (Non Return to Zero - Space) 72 NRZ (M) (Non Return to Zero - Mark) 72 Bi-Ф-L (Biphase Level) 72 Bi-Ф-S (Biphase Space) 72 Bi-Ф- M (Biphase Mark) 72 

1.6  Coding 73 Code 73 Codes in communication used for brevity 73 An example: the ASCII code 73 Interleaving in error-correction coding 74 Interleaving examples 74 Codes to detect or correct errors 75 Error-correcting code (ECC) 75 Forward Error Correction (FEC) 75 Convolutional code 76 Viterbi algorithm 77 

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Reed-Solomon error correction 77 Overview of the method 77 Properties of Reed-Solomon codes 78 Use of Reed-Solomon codes in optical and magnetic storage 78 Timeline of Reed-Solomon development 79 Satellite technique: Reed-Solomon + Viterbi coding 79 

Turbo code 79 Shannon-Hartley theorem 80 

Theorem 80 Examples 81 

1.7  Used code tables 82 ITA2, ITA2P and ITA3(CCIR342-2) 82 Russian MTK2 83 CCIR476-4, HNG-FEC, PICCOLO MK VI 84 

ITA 2 P 85 ITA 3 85 CCIR 476 85 ASCII / CCITT 5 85 

1.8  Channel access methods 91 Frequency-division multiple access (FDMA) 91 Time division multiple access (TDMA) 91 Code division multiple access (CDMA) 92 Orthogonal Frequency multiple access (OFDMA) 92 

1.9  The OSI Reference Model 93 The Physical Layer 93 The Data Link Layer 94 The Network Layer 94 The Transport Layer 95 The Session Layer 96 The Presentation Layer 96 The Application Layer 96 

1.10  Protocols 97 Automatic repeat ReQuest Protocol (ARQ protocol) 97 

Pure Stop and Wait ARQ 97 Go Back N ARQ 98 Selective Repeat ARQ 98 Polling 98 

ACP127 99 STANAG 4406 Messaging 99 STANAG 5066 100 X.25 101 RSX.25 106 Automatic Link Establishment (ALE) 107 Codan Automated Link Management (CALM) 109 

1.11  Designation of Emissions 110 

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Determination of Necessary Bandwidths 114 

1.12  Table of system and user sorted by Baud rate 123 

6  HF MODES 137 

General Information 137 Spectrum 137 Sonagram 137 Oscilloscope 137 Phase Spectrum 137 Phase Plane 138 Speed Bit Analyses 138 Bit Correlation, Autocorrelation Function (ACF) 138 

1.  AFS Navy FSK 139 2.  ALE 3G 139 3.  ALE400 142 4.  ALIS 143 5.  ALIS 2 144 6.  ARD9800 OFDM 36ch Modem 145 7.  ARQ-E 146 8.  ARQ-E3 146 9.  ARQ-M2 148 10.  ARQ-M4 148 11.  ARQ-S 149 12.  ARQ-SWE 150 13.  ARQ 6-70S 151 14.  ARQ 6-90/98 151 15.  ASCII 152 16.  AUM-13 152 17.  AUS MIL ISB Modem 153 18.  AUTOSPEC 154 19.  Baudot ITA No.2 155 

Baudot Code 156 Murray Code 156 Western Union Code 157 ITA2 Code 157 

20.  Baudot–ARQ System 158 21.  Baudot F7B 158 22.  Baudot Sync 159 23.  BEE 160 24.  BR 6028 160 25.  BR 6029C Time Diversity Modem 161 26.  BUL 107.53 Bd 162 27.  BUL ASCII 162 28.  CCIR 493 SELCALL 163 29.  CHN MIL 4MFSK 164 30.  CHN MIL 8MFSK 165 31.  CHN MIL 64FSK 166 32.  CHN MIL Hybrid Modem (4FSK-OFDM20) 168 

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33.  CHN MIL Hybrid Modem (4FSK-8FSK-OFDM19) 169 34.  CHN MIL Hybrid Modem (8FSK-PSK) 170 35.  CHN 4+4 Modem 172 36.  CHIP 64/128 173 37.  CIS 11 174 38.  CIS 12 175 39.  CIS 12 ARQ 176 40.  CIS 14 177 41.  CIS 150 Bd SELCAL 177 42.  CIS 16x75 Bd 178 43.  CIS 36-50 179 44.  CIS 405-3915 180 45.  CIS 50-17 Baudot 181 46.  CIS 50-50 182 47.  CIS 81-29 183 48.  CIS 81-81 184 49.  CIS 200-1000 184 50.  CIS 500 Bd FSK Burst Modem 185 51.  CIS 1280 Bd Modem 186 52.  CIS 3000 Bd Modem 187 53.  CIS 4FSK 96 Bd 187 54.  CIS 4FSK 100 Bd 188 55.  CIS 4FSK 150 Bd 189 56.  CIS-ARQ 190 57.  CIS AT-3004 Modem 192 58.  CIS BPSK 192 59.  CIS MFSK-20 194 60.  CIS 45/60/93/112/128 Channel OFDM 195 

45 tone OFDM variant 1 195 45 tone OFDM variant 2 195 45 tone OFDM variant 3 195 60 tone OFDM variant 1 196 60 tone OFDM variant 2 196 93 tone OFDM 196 112 tone OFDM 197 128 tone OFDM 197 

61.  CIS VFT 3 Channels 100 Bd 198 62.  CIS VFT 3 Channels 144 Bd 198 63.  Clansman FSK Modem 200 64.  Clover 200 65.  Clover II 202 66.  Clover 2000 203 

Error-Correction Coding 204 Selective ARQ Repeat 205 Signal Format 205 Modulation Formats 205 Data Modes 205 Data Throughput (Bps) 205 

67.  Clover 2500 206 68.  Coachwhip 207 69.  CODAN 207 

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CODAN 4 Channel mode 208 CODAN 8 Channel Mode 208 CODAN 12 Channel Mode 209 

70.  CODAN Chirp mode 209 71.  CODAN Selcall 210 72.  Contestia 211 73.  Coquelet 8 212 74.  Coquelet 8 FEC 214 75.  Coquelet 100 214 76.  Coquelet 13 215 77.  CROWD 36 216 78.  CROWD 36 Selective Calling 217 79.  CW 218 80.  CW-F1B 219 81.  D AF VFT 219 82.  DGPS 219 

TX numbers 220 Message types 221 

Type 3 Message 221 Type 5 Message 221 Type 7 Message 221 Type 9 Message 221 Type 9-3 Message 221 Type 9-1 Message 222 Type 16 Message 223 

DGPS Message Scheduling 223 Type 3 Message 223 Type 5 Message 223 Type 7 Message 223 Type 9 Message 224 Type 16 Message 224 

83.  DominoF 224 84.  DominoEX 225 85.  DPRK ARQ 600 Bd 226 86.  DPRK ARQ 1200 Bd 228 87.  DPRK FSK 600 FEC 229 88.  DPRK BPSK Modem 229 

DPRK 150 Bd BPSK 230 DPRK 300 Bd BPSK 230 DPRK 600 Bd BPSK 230 DPRK 1200 Bd BPSK 231 

89.  DRM 231 Stream Multiplexer 232 Fast Access Channel (FAC) 232 Service Description Channel (SDC) 233 Main Service Channel (MSC) 233 Transmission Frame 233 MPEG-4 234 Advanced Audio Encoding (AAC) 234 MPEG CELP 234 Harmonic Vector Excitation Coding 234 

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Multilevel Coding 234 90.  DRM – WinDRM 235 91.  DUP-ARQ 236 92.  DUP-ARQ II 238 93.  DUP-FEC II 238 94.  ECHOTEL 1810 HF Modem 239 95.  ECHOTEL 1820 HF Modem 239 96.  F7B-195.3 Bd 4-Tone 241 97.  Fax 242 98.  FEC-A 246 99.  G-TOR 246 100.  Globe Wireless Pactor 248 101.  Globe Wireless Single Tone Modem 249 102.  Globe Wireless Multi Tone Modem 250 

Globe Wireless OFDM with 12 carriers 250 Globe Wireless OFDM with 24 carriers 251 Globe Wireless OFDM with 32 carriers 251 

103.  GRC MIL FSK 252 104.  GMDSS-DSC HF 252 105.  HC-ARQ 253 106.  HDSSTV 254 107.  HELL 255 

F-Hell, Press-Hell 255 Feld-Hell 255 GL-Hell 256 Hell-80 256 PC-Hell 257 PSK-Hell and FM-Hell 257 FSK-Hell 258 Duplo-Hell 259 Sequential Multi-Tone Hell 259 Concurrent Multi-Tone Hell 260 Slow-Feld 260 

108.  HFDL 261 109.  HNG-FEC 265 110.  ICAO Selcal 265 111.  IRA-ARQ 267 112.  IRN Navy 16 x 75 Bd 268 113.  IRN Navy QPSK 207 Bd 269 114.  IRN Navy Adaptive Modem V1 271 115.  IRN Navy Adaptive Modem V2 273 116.  ISR N Hybrid Modem 273 117.  Italian MIL 1200 Bd FSK 274 118.  Italian MIL 1200 Bd PSK 274 119.  Japan 8-Tone ASK 274 120.  Japan 16-tone PSK 275 121.  Japan 1500 Bd QPSK 276 122.  Japan 32-tone OFDM 277 123.  JT2 278 124.  JT44 279 125.  JT6M 280 

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126.  JT65A/JT65B/JT65C 281 127.  LINCOMPEX 283 128.  LINEA Sitor 283 129.  LINK 1 284 130.  LINK 10 284 131.  LINK 11 CLEW 284 132.  LINK 11 SLEW 287 133.  LINK 14 288 134.  LINK 22 289 135.  LINK Y 290 136.  LINK Z 290 137.  Mazielka 291 138.  MD 522 NB 291 139.  MD 522 WB 292 140.  MD 522 DIV 292 141.  MD 1061 293 142.  MD 1142 294 143.  MD 1280 295 144.  MFSK-8 295 145.  MFSK-16 296 146.  MFSK AFS Navy Modem 297 147.  MFSK BUL 8-Tone 297 148.  MFSK Modem ALCATEL 801 298 

MFSK 4-TONE ARQ SYSTEM 150 to 1200 Bd 298 MFSK 8-TONE ARQ SYSTEM 16.7 & 100 Bd 299 

149.  MFSK TADIRAN HF Modem 299 150.  MFSK TE-204/USC-11 Modem 299 151.  MFSK Thrane & Thrane TT2300-ARQ Modem 301 152.  MFSK YUG 20-Tone Modem 301 153.  MIL STD 188-110A ser 302 154.  MIL STD 188-110A Appendix A 16-Tone 303 155.  MIL STD 188-110A Appendix B 39-Tone 304 156.  MIL STD 188-110B App C 304 157.  MIL STD 188-110B Appendix F 306 158.  MIL STD 188-110C Appendix D 306 159.  MIL STD 188-141A 307 

Linking Protection 307 AL-0 308 AL-1 308 AL-2 308 AL-3 308 AL-4 (classified application level) 309 

Alternate Quick Call (AQC) ALE 309 160.  MIL STD 188-141B Appendix A 309 161.  MIL STD 188-141B Appendix C 309 162.  MIL STD 188-203-1A 310 163.  MIL STD 188-203-3 310 164.  MIL STD 188-212 310 165.  MIL STD 188-342 310 166.  MLA Navy Baudot 311 167.  MT 63 312 

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168.  Nokia Adaptive Burst Modem 313 169.  NUM 13 314 170.  Olivia 315 

Olivia MFSK layer 316 Olivia Walsh functions FEC layer 317 

171.  PACTOR I 318 172.  PACTOR II 318 173.  PACTOR II-FEC 320 174.  PACTOR III 320 175.  PACTOR IV 323 

PACTOR VI 2-Tone-Chirp 324 PACTOR IV Spread Modulation 324 

176.  Packet Radio 324 177.  Panther-H FH Modem 325 178.  PAX/PAX2 326 179.  PICCOLO Mark VI 327 180.  PICCOLO 12 331 181.  POL-ARQ 334 182.  PSK 10 334 183.  PSK 31 336 184.  PSK 63 FEC 337 185.  PSK 125 FEC 337 186.  PSK 220 FEC 338 187.  PSKAM 10/31/50 338 188.  Q15x25 341 189.  RAC-ARQ 341 190.  RFSM 2400/8000 342 

RFSM-2400 Modem 342 RFSM-8000 Modem 343 

191.  Robust Packet Radio RPR 343 192.  ROS 344 193.  ROU-FEC 345 194.  RS-ARQ 346 195.  RS-ARQ II 347 196.  RS GM2xxx Modem 347 197.  RS GN2130 Modem 349 198.  RTTYM 350 199.  RUS Mil Voice Scrambler 351 200.  Selenia Parallel Tone Modem 351 201.  Siemens CHX-200 FSK Modem 352 202.  SITOR A/B 353 

ARQ mode A 353 FEC mode B 353 

203.  SKYFAX 354 204.  SSTV 357 SSTV VIS-Code 359 205.  STANAG 4197 361 206.  STANAG 4198 362 207.  STANAG 4202 363 208.  STANAG 4285 364 209.  STANAG 4415 365 

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210.  STANAG 4444 366 211.  STANAG 4479 367 212.  STANAG 4481 FSK 368 213.  STANAG 4481 PSK 368 214.  STANAG 4529 369 215.  STANAG 4538 370 216.  STANAG 4539 371 217.  STANAG 4591 371 218.  STANAG 5031 372 219.  STANAG 5035 372 220.  STANAG 5065 372 221.  Systeme 3000 HF Modem 373 222.  Tadiran AutoCall 373 223.  Tadiran Data Mode 374 224.  TFM3/5 375 225.  Thales Voice Scrambler 376 226.  Throb 377 227.  TMS-430 Modem 377 228.  TWINPLEX 378 229.  VFT 380 230.  VISEL 381 231.  WINMOR 382 

7  OTHER ACTIVE SYSTEMS ON HF 386 232.  AMSS 386 233.  Advanced Narrowband Digital Voice Terminal (ANDVT) Family 387 

TACTERM 387 MINTERM 388 AIRTERM 388 

234.  Beacons 389 Maritime Mobile Service (MMS) Beacon 389 Aeronautical Mobile Service (AMS) Beacon 389 Amateur Radio Beacon 389 Single Letter Beacons (SLB) 391 

235.  Analogue Voice Scrambler Sailor CRY-2001 392 236.  Buoys 393 

Drifting buoys 393 Fishing Buoys 394 Sel-Call Buoys 394 

237.  Buoy Directional Waverider DWR-MkIII 394 238.  Chirpsounder 395 

Chirpcomm 397 239.  CODAR 397 240.  Datatrak 399 241.  Digisonde 4D 400 242.  EFR 402 243.  Eurofix 403 244.  Long Range Ocean Radar 404 245.  LORAN-C 405 

LORAN data channel communication (LDC) 406 

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Ninth-Pulse Modulation 406 Messages 407 

246.  MF RADAR 407 247.  NAVTEX 408 248.  NBTV 410 249.  OFDM NBTV 411 

Limitations 412 The OFDM NBTV Modes 412 

48 x 48 Mode 412 96 x 72 Mode 413 96 x 72 Mode 413 

250.  Digital NBTV 414 Modem 416 Codec 417 Interpolation 417 Compression 417 Error Correction 418 Data Transmission 418 Transmission Speed 418 

251.  Hybrid FM NBTV 418 PN Sequence Sync 419 Operating Modes 419 Modulation 420 

252.  NDS200 DGPS 421 253.  Over The Horizon Radar 423 254.  RFID 425 255.  Russian ALPHA and LORAN-C System 426 256.  Russian BRAS-3 and RS-10 System 427 257.  Super Dual Auroral Radar Network 430 258.  Time Signal Stations 432 259.  WERA 433 

8  TABLES FOR RADIO MONITORING 438 

1.13  Allocation of International Call Signs 438 

1.14  Alphabetical List of Country Codes 442 

1.15  Selective Calling 446 

1.16  Allocation of Maritime Identification Digits 450 

1.17  NATO Routing Indicators 456 

1.18  Aeronautical Fixed Telecommunication Network 462 

1.19  AFTN Messages 464 Standard Messages 464 

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1.20  Notice to Airmen (NOTAM) 466 TAF 473 METAR 473 

1.21  Teleprinter Alphabets 476 

1.22  ATU 80 Words Identification 478 

1.23  Arabic words identification 481 

1.24  Q , X and Z - Code 484 Q-Codes 484 X-Codes 494 Z-Codes 496 

1.25  Abbreviations 506 

9  INDEX 514 

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1 List of Pictures

Picture 1: Different AM waveforms ................................................................................................. 37 Picture 2: Spectrum and sonagram of an amplitude modulation .................................................... 38 Picture 3: Spectrum of a double sideband suppressed carrier signal ............................................. 39 Picture 4: Spectrum and sonagram of a single sideband modulation with full carrier ................... 39 Picture 5: Spectrum and sonagram of a single sideband modulation with reduced carrier ........... 40 Picture 6: Spectrum of a single sideband modulation ..................................................................... 41 Picture 7: Spectrum of an independent modulated signal ............................................................... 41 Picture 8: Frequency Modulation .................................................................................................... 42 Picture 9: Spectrum and sonagram of a frequency modulation ...................................................... 43 Picture 10: Spectrum of a wide FM broadcast transmitter ............................................................. 43 Picture 11: Audio chanels of a broadcast signal ............................................................................ 44 Picture 12: Spectrum of FM stereo signal with sub-channels ......................................................... 44 Picture 13: Amplitude Shift Keying (ASK) ....................................................................................... 46 Picture 14: Spectrum of an ASK with 100 Bd .................................................................................. 46 Picture 15: On-Off-Keying OOK ..................................................................................................... 47 Picture 16: Oscilloscope display of an OOK ................................................................................... 47 Picture 17: Frequency Shift Keying (FSK) ...................................................................................... 47 Picture 18: Spectrum of an FSK ...................................................................................................... 48 Picture 19: Spectrum of a CPFSK with 100 Bd ............................................................................... 48 Picture 20: Spectrum of a DFSK ..................................................................................................... 49 Picture 21: IQ Plot of C4FM ........................................................................................................... 50 Picture 22: Sonagram and spectrum of C4FM in idle mode ........................................................... 50 Picture 23: Minimum Shift Keying ................................................................................................... 51 Picture 24: Spectrum of a Tamed Frequency Modulation (TFM 3) with 100 Bd ............................ 51 Picture 25: Spectrum of a MFSK with 12 tones ............................................................................... 52 Picture 26: Phase shift Keying ......................................................................................................... 53 Picture 27: BPSK-A ......................................................................................................................... 53 Picture 28: Phase plane of a BPSK ................................................................................................. 54 Picture 29: Spectrum of a BPSK with 600 Bd ................................................................................. 54 Picture 30: BPSK-B ......................................................................................................................... 54 Picture 31: QPSK-A ......................................................................................................................... 55 Picture 32: QPSK-B ......................................................................................................................... 56 Picture 33: Spectrum of a QPSK with 600 Bd ................................................................................. 56 Picture 34: Phase plane of a QPSK ................................................................................................. 56 Picture 35: Phase plane of an OQPSK (right) compared to QPSK (left) ........................................ 57 Picture 36: Phase Plane of an 8PSK ............................................................................................... 58 Picture 37: Spectrum of an 8PSK with 600 Bd ................................................................................ 59 Picture 38: Example of an 8QAM and 16QAM in the Phase Plane ................................................ 60 Picture 39: Spectrum of a QAM8 with 600 Bd ................................................................................ 61 Picture 40: Spectrum of a QAM16 with 600 Bd .............................................................................. 61 Picture 41: Comparison of FDM and OFDM ................................................................................. 62 Picture 42: Spectrum of OFDM with 45 channels ........................................................................... 62 Picture 43: Function of DSSS .......................................................................................................... 63 Picture 44: Function of FHSS .......................................................................................................... 64 

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Picture 45: Different types of amplitude modulation ...................................................................... 65 Picture 46: Quantization in a PCM ................................................................................................. 66 Picture 47: Delta Modulation .......................................................................................................... 67 Picture 48: Common data formats .................................................................................................. 71 Picture 49: Principle of FDMA ....................................................................................................... 91 Picture 50: Principle of TDMA ....................................................................................................... 91 Picture 51: Principle of OFDMA .................................................................................................... 92 Picture 52: The OSI reference model .............................................................................................. 93 Picture 53: Basic elements of the ARQ protocol ............................................................................. 97 Picture 54: ARQ stop and wait ........................................................................................................ 97 Picture 55: Go Back N method ........................................................................................................ 98 Picture 56: Selective repeat ARQ method ....................................................................................... 98 Picture 57: STANAG 5066 layers .................................................................................................. 100 Picture 58: Spectrum of an AFS navy modem ............................................................................... 139 Picture 59: Spectrum of an ALE 3G .............................................................................................. 139 Picture 60: Phase constellation of an ALE 3G 8PSK signal ......................................................... 140 Picture 61: Dwell structure of an ALE 3G .................................................................................... 140 Picture 62: ALE 3G protocol data units ........................................................................................ 141 Picture 63: Spectrum of ALE400 ................................................................................................... 142 Picture 64: Expanded spectrum of ALE400 .................................................................................. 142 Picture 65: Spectrum of an ALIS signal ........................................................................................ 143 Picture 66: Sonagram ALIS link setup procedure ......................................................................... 144 Picture 67: Spectrum of ALIS 2 ..................................................................................................... 144 Picture 68: Spectrum of ARD9800-OFDM ................................................................................... 145 Picture 69: Spectrum and Sonagram of ARD9800-OFDM ........................................................... 145 Picture 70: Spectrum of an ARQ-E signal with 288 Bd ................................................................ 146 Picture 71: Spectrum of ARQ-E3 in idle mode .............................................................................. 147 Picture 72: ARQ-E3 – Signal Structure ........................................................................................ 147 Picture 73: Typical spectrum of an ARQ-M4 ................................................................................ 149 Picture 74: Spectrum of ARQ-SWE ............................................................................................... 150 Picture 75: Spectrum of an ARQ 6-90 ........................................................................................... 151 Picture 76: Oscilloscope display of ARQ 6-90 .............................................................................. 152 Picture 77: Spectrum of AUM 13 signal ....................................................................................... 153 Picture 78: Spectrum of the AUS MIL ISB modem with both waveforms ..................................... 153 Picture 79: Spectrum of the 50 Bd waveform ................................................................................ 154 Picture 80: Spectrum of the 600 Bd waveform .............................................................................. 154 Picture 81: Spectrum of AUTOSPEC with 75 Bd .......................................................................... 154 Picture 82: Spectrum of a 150 Bd Baudot signal .......................................................................... 155 Picture 83: Baudot signal in the oscilloscope display ................................................................... 155 Picture 84: Bit correlation of a Baudot signal .............................................................................. 156 Picture 85: Hell display of a Baudot signal .................................................................................. 156 Picture 86: Spectrum of the Russian Baudot-ARQ system ............................................................ 158 Picture 87: Spectrum of Baudot F7B with 50 Bd .......................................................................... 158 Picture 88: Sonagram of Baudot F7B ........................................................................................... 159 Picture 89: Spectrum of Baudot Sync ............................................................................................ 159 

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Picture 90: Baudot sync display speed in relation to bit ............................................................... 159 Picture 91: Spectrum of a CIS 36-50 signal .................................................................................. 160 Picture 92: Spectrum of a BR6028 signal ...................................................................................... 161 Picture 93: Spectrum of BUL 107.53 Bd ....................................................................................... 162 Picture 94: Spectrum and sonagram of a BUL ASCII signal ........................................................ 163 Picture 95: Spectrum CCIR 493-4 ................................................................................................. 163 Picture 96: Spectrum of CHN MIL 4FSK 500 Hz variant ............................................................. 165 Picture 97: Spectrum of CHN MIL 4FSK 400 Hz variant ............................................................. 165 Picture 98: Sonagram of CHN MIL 4FSK 500 Hz variant ............................................................ 165 Picture 99: Spectrum of CHN MIL 8FSK ...................................................................................... 166 Picture 100: Sonagram of CHN MIL 8FSK ................................................................................... 166 Picture 101: Spectrum of the CHN 64FSK .................................................................................... 167 Picture 102: Zoomed spectrum of the CHN 64FSK ....................................................................... 167 Picture 103: Sonagram of CHN 64 tone MFSK ............................................................................ 167 Picture 104: Post sequence of the CHN 64FSK............................................................................. 167 Picture 105: Spectrum CHN hybrid modem 4FSK-OFDM20 ....................................................... 168 Picture 106: Sonagram CHN hybrid modem 4FSK-OFDM20 ...................................................... 169 Picture 107: Spectrum of the 19 tone OFDM ................................................................................ 170 Picture 108: Preamble of the CHN hybrid modem 8FSK-OFDM19 ............................................. 170 Picture 109: Sonagram of CHN MIL Hybrid modem 8FSK-QPSK ............................................... 171 Picture 110: 8FSK preamble for CHN MIL Hybrid modem .......................................................... 171 Picture 111: PSK preamble for CHN MIL Hybrid modem ............................................................ 172 Picture 112: Spectrum of MFSK 4+4 signal ................................................................................. 172 Picture 113: Spectrum of a CHIP64 signal ................................................................................... 173 Picture 114: Phase plane of a CHIP signal ................................................................................... 173 Picture 115: Phase spectrum of a CHIP 64 signal ........................................................................ 174 Picture 116: Phase oscilloscope display of a CHIP 64 signal ...................................................... 174 Picture 117: Spectrum of CIS-11 ................................................................................................... 175 Picture 118: CIS12/MS5 spectrum with reference tone ................................................................. 175 Picture 119: CIS 12/MS2 spectrum in idle mode ........................................................................... 175 Picture 120: CIS 20 spectrum with reference tone ...................................................................... 176 Picture 121: CIS 20 averaged sonagram ....................................................................................... 176 Picture 122: CIS 12 ARQ bursts .................................................................................................... 176 Picture 123: Spectrum of CIS 14 with 96 Bd and 1000 Hz shift .................................................... 177 Picture 124: Auto correlation display of CIS 14 with ACF at 14 bit ............................................. 177 Picture 125: Spectrum of CIS 150 Bd selcall ................................................................................ 178 Picture 126: Spectrum of CIS 16x75 Bd ........................................................................................ 178 Picture 127: Phase plane of one channel ...................................................................................... 178 Picture 128: Spectrum and sonagram of CIS 16x75 Bd ................................................................ 179 Picture 129: Spectrum of a CIS 36-50 in idle condition ................................................................ 180 Picture 130: Message structure of a CIS 36-50, T600 .................................................................. 180 Picture 131: Spectrum and sonagram of a CIS 40.5/1000 signal ................................................. 181 Picture 132: Spectrum of CIS 50-17 Baudot FROST2 .................................................................. 181 Picture 133: HELL display of CIS 50-17 Baudot FROST2 ........................................................... 182 Picture 134: Auto correlation function (ACF) of CIS 50-17 Baudot FROST2 .............................. 182 

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Picture 135: Spectrum of a CIS 50-50 in idle condition ............................................................... 182 Picture 136: Oscilloscope display of a CIS 50-50 in idle condition ............................................. 183 Picture 137: Spectrum and sonagram of a CIS 81-29 ................................................................... 183 Picture 138: Typical spectrum of an 8181 signal with 500 Hz shift .............................................. 184 Picture 139: Spectrum of a CIS 200-1000 signal .......................................................................... 184 Picture 140: ACF of a CIS 200-1000 ............................................................................................ 185 Picture 141: Spectrum of CIS 500 FSK burst ................................................................................ 185 Picture 142: Sonagram of CIS 500 FSK burst .............................................................................. 185 Picture 143: Spectrum of CIS 1280 Bd modem ............................................................................. 186 Picture 144: Phase Plane of CIS 1280 Bd modem ........................................................................ 186 Picture 145: Spectrum of CIS 3000 Bd 8PSK modem ................................................................... 187 Picture 146: Speed measurement of CIS 3000 Bd 8PSK modem .................................................. 187 Picture 147: Spectrum of a CIS 4FSK with 96 Bd ......................................................................... 188 Picture 148: Tones of a CIS 4FSK with 96 Bd .............................................................................. 188 Picture 149 : MFSK display of a CIS 4FSK with 96 Bd ................................................................ 188 Picture 150: Spectrum of a CIS 4FSK with 100 Bd and 500 Hz shift ........................................... 189 Picture 151: MFSK demodulation of a CIS 4FSK with 100 Bd and 500 Hz shift ......................... 189 Picture 152: Spectrum of a CIS 4FSK with 4000 Hz channel shift ............................................... 189 Picture 153: Sonagram of a CIS 4FSK with 4000 Hz shift ........................................................... 190 Picture 154: Spectrum of the CIS ARQ ......................................................................................... 190 Picture 155: Sonagram of the CIS ARQ ........................................................................................ 191 Picture 156: FSK oscilloscope display of the CIS ARQ ................................................................ 191 Picture 157: Spectrum of CIS 1200 Bd modem ............................................................................. 192 Picture 158: Spectrum CIS BPSK system ...................................................................................... 193 Picture 159: Phase spectrum of CIS BPSK ................................................................................... 193 Picture 160: Spectrum of MFSK-20 .............................................................................................. 194 Picture 161: Sonagram of MFSK-20 ............................................................................................. 194 Picture 162: spectrum of a CIS 45 tone OFDM ............................................................................ 195 Picture 163: Spectrum of a CIS 60 tone OFDM............................................................................ 196 Picture 164: Spectrum of a CIS 93 tone OFDM............................................................................ 196 Picture 165: Spectrum of CIS 93 tone OFDM shifted by 550 Hz .................................................. 197 Picture 166: Spectrum of a CIS 112 tone OFDM.......................................................................... 197 Picture 167: Spectrum of a CIS 128 toe OFDM............................................................................ 198 Picture 168: Spectrum of a CIS VFT 3 Channels 100 bd .............................................................. 198 Picture 169: Spectrum of a CIS VFT 3 channels 144 bd ............................................................... 199 Picture 170: Spectrum of the Clansman FSK modem ................................................................... 200 Picture 171: Spectrum of a CLOVER signal ................................................................................. 201 Picture 172: Sonagram of a CLOVER signal ................................................................................ 201 Picture 173: Spectrum of Clover in 8P2A mode ........................................................................... 204 Picture 174: Spectrum of CODAN 16 channel mode .................................................................... 208 Picture 175: CODAN 4 channel mode .......................................................................................... 208 Picture 176: CODAN 8 channel mode .......................................................................................... 209 Picture 177: CODAN 12 channel mode ........................................................................................ 209 Picture 178: Spectrum of CODAN chirp selcall ............................................................................ 210 Picture 179: Spectrum of CODAN Selcall ..................................................................................... 210 

23

Picture 180: Spectrum and sonagram of Contestia 4-250 mode ................................................... 211 Picture 181:: Spectrum and sonagram of Contestia 8-1000 mode ................................................ 212 Picture 182:: Spectrum and sonagram of Contestia 32-1000 mode .............................................. 212 Picture 183: Example of Coquelet-8 decoding .............................................................................. 213 Picture 184: MFSK Coquelet-8 signal ........................................................................................... 214 Picture 185: Spectrum of Coquelet 100 with 16.7 Bd .................................................................... 215 Picture 186: Spectrum of Coquelet 13 ........................................................................................... 216 Picture 187: Spectrum of CROWD 36 ........................................................................................... 217 Picture 188: Crowd 36 in sonagram display ................................................................................. 217 Picture 189: Spectrum of CROWD 36 selective calling ................................................................ 218 Picture 190: Sonagram of CROWD 36 selective calling ............................................................... 218 Picture 191: Spectrum of a D AF VFT signal ................................................................................ 219 Picture 192: Spectrum of a DGPS signal with 100 Bd .................................................................. 220 Picture 193: Spectrum of DominoEX with 4 Bd ............................................................................ 225 Picture 194: Spectrum of DominoEX with 11 Bd .......................................................................... 226 Picture 195: Spectrum of DominoEX with 22 Bd .......................................................................... 226 Picture 196: Spectrum of DPRK FSK in ARQ mode ..................................................................... 226 Picture 197: Sonagram of DPRK FSK in ARQ mode .................................................................... 227 Picture 198: Different sonagram of DPRK FSK in ARQ mode ..................................................... 227 Picture 199: ACF of DPRK ARQ with 600 Bd .............................................................................. 228 Picture 200: Data packets of a DPRK ARQ with 1200 Bd ............................................................ 228 Picture 201: Spectrum of a DPRK ARQ 1200 Bd .......................................................................... 229 Picture 202: Spectrum of DPRK FSK 600 FEC ............................................................................ 229 Picture 203: Spectrum of a DPRK BPSK modem with 150 Bd ...................................................... 230 Picture 204: Spectrum of a DPRK BPSK modem with 300 Bd ...................................................... 230 Picture 205: Spectrum of a DPRK BPSK modem with 600 Bd ...................................................... 230 Picture 206: Spectrum of a DPRK BPSK modem with 1200 Bd .................................................... 231 Picture 207: Spectrum of DRM-OFDM ......................................................................................... 231 Picture 208: Framing OFDM ........................................................................................................ 233 Picture 209: Spectrum of WinDRM ............................................................................................... 236 Picture 210: Spectrum of DUP ARQ ............................................................................................. 236 Picture 211: Spectrum of MAHRS with 2400 Bd ........................................................................... 239 Picture 212: Spectrum of FARCOS mode ...................................................................................... 240 Picture 213: Phase spectrum of FARCOS with peaks at 1800 Hz ................................................. 240 Picture 214: Spectrum of F7B 195.3 Bd ........................................................................................ 241 Picture 215: Sonagram of F7B 195.3 Bd ....................................................................................... 242 Picture 216: Spectrum of a FAX transmission ............................................................................... 242 Picture 217: Typical picture of a FAX transmission ..................................................................... 243 Picture 218: Spectrum of a FEC-A with 192 Bd ............................................................................ 246 Picture 219: Spectrum of a G-TOR signal with 300 Bd ................................................................ 247 Picture 220: Sonagram of a G-TOR signal ................................................................................... 248 Picture 221: Spectrum of GW Single Tone Modem ....................................................................... 249 Picture 222: Phase Plane of GW Single Tone Modem .................................................................. 249 Picture 223: Sonagram GW Multi Tone Modem with 30 tones ..................................................... 250 Picture 224: Spectrum of a Globe Wireless OFDM with 12 carriers ............................................ 250 

24

Picture 225: Spectrum of a Globe Wireless OFDM with 24 carriers ........................................... 251 Picture 226: Spectrum of a Globe Wireless OFDM with 32 carriers ........................................... 251 Picture 227: Spectrum of GRC MIL FSK ...................................................................................... 252 Picture 228: Preamble of the GRC MIL FSK ................................................................................ 252 Picture 229: Spectrum of GMDSS-DSC ........................................................................................ 253 Picture 230: Spectrum of DSSTV .................................................................................................. 254 Picture 231: Sonagram of DigiTRX with embedded callsign ........................................................ 254 Picture 232: Matrix Feld Hell ....................................................................................................... 255 Picture 233: Spectrum of a typical Feld-Hell signal ..................................................................... 255 Picture 234: Feld Hell modulation ................................................................................................ 256 Picture 235: Sonagram of a Feld-Hell signal ............................................................................... 256 Picture 236: Matrix of GL-Hell ..................................................................................................... 256 Picture 237: Spectrum of a PSK-Hell signal ................................................................................. 257 Picture 238: Phase spectrum of a PSK-Hell signal ....................................................................... 258 Picture 239: Phase constellation of a PSK-Hell signal ................................................................. 258 Picture 240: Spectrum of a FSK-Hell signal ................................................................................. 259 Picture 241: Sonagram of a FSK-Hell signal ............................................................................... 259 Picture 242: Spectrum of a HFDL signal ...................................................................................... 261 Picture 243: Sonagram of a HFDL signal with sub-carrier of 1440 Hz ....................................... 261 Picture 244: Framing of HFDL ..................................................................................................... 262 Picture 245: Oscilloscope display of HNG-FEC ........................................................................... 265 Picture 246: Typical spectrum of ANNEX 10 with two tone pairs ................................................ 266 Picture 247: Timing of the ICAO SELCAL .................................................................................... 266 Picture 248: Oscilloscope display of IRA-ARQ ............................................................................. 267 Picture 249: Spectrum of IRA-ARQ with 600 Bd .......................................................................... 267 Picture 250: Spectrum of an IRN Navy 16 x 75 Bd modem ........................................................... 268 Picture 251: IRN N 16 x 75 Bd modem with precarrier ................................................................ 268 Picture 252: Phase spectrum of one channel with 75 Bd .............................................................. 269 Picture 253: Spectrum of IRN 207 Bd modem .............................................................................. 269 Picture 254: Phase spectrum of IRN 207 Bd signal with peaks at 207 Bd .................................... 270 Picture 255: Phase plane of IRN QPSK 207 Bd modem ............................................................... 270 Picture 256: Sonagram of IRN QPSK 207 Bd ............................................................................... 271 Picture 257: Spectrum of the adaptive IRN N QPSK modem with 414 Bd ................................... 271 Picture 258: Speed measurement of the adaptive IRN N QPSK modem with 414 Bd ................... 272 Picture 259:Speed measurement of the adaptive IRN N QPSK modem with 828 Bd .................... 272 Picture 260: Spectrum of the adaptive IRN N QPSK modem with 1656 Bd ................................. 272 Picture 261: Speed measurement of the adaptive IRN N QPSK modem with 1656 Bd ................. 272 Picture 262: Spectrum of 1200 Bd FSK ........................................................................................ 274 Picture 263: Spectrum of Italian MIL PSK 1200 Bd ..................................................................... 274 Picture 264: Spectrum of Japan 8-tone ASK ................................................................................. 275 Picture 265: Sonagram of Japan 8-tone ASK ............................................................................... 275 Picture 266: Spectrum of Japan 16tone PSK ................................................................................ 276 Picture 267: Sonagram of Japan 16tone PSK ............................................................................... 276 Picture 268: Spectrum of the Japan 1500 Bd QPSK ..................................................................... 276 Picture 269: Speed measurement of the Japan 1500 Bd QPSK .................................................... 277 

25

Picture 270: Phase constellation of the Japan 1500 Bd QPSK ..................................................... 277 Picture 271: Sonagram of Japan 32-tone OFDM ......................................................................... 278 Picture 272: Spectrum and sonagram of a JT2 signal ................................................................... 279 Picture 273: Spectrum and sonagram of a JT44 signal ................................................................. 280 Picture 274: Spectrum and sonagram of a JT6M signal ............................................................... 281 Picture 275: Sonagram of JT65A signal ........................................................................................ 282 Picture 276: Sonagram of JT65B signal ........................................................................................ 282 Picture 277: Sonagram of JT65C signal ....................................................................................... 282 Picture 278: Spectrum of a LINCOMPEX signal with two channels ............................................ 283 Picture 279: Spectrum of LINEA Sitor .......................................................................................... 283 Picture 280: Spectrum of a LINK 11 transmission ........................................................................ 285 Picture 281: Spectrum of the LINK 11 single Tone Modem .......................................................... 288 Picture 282: Sonagram of LINK 11 SLEW .................................................................................... 288 Picture 283: Typical spectrum of a LINK 14 signal ...................................................................... 289 Picture 284: Spectrum of Mazielka ................................................................................................ 291 Picture 285: Sonagram of Mazielka .............................................................................................. 291 Picture 286: Spectrum of MD 522 NB ........................................................................................... 292 Picture 287: Spectrum of a MD 522 WB ....................................................................................... 292 Picture 288: Spectrum of a MD 522 DIV ...................................................................................... 293 Picture 289: Sonagram and spectrum of a MD 522 DIV .............................................................. 293 Picture 290: Spectrum of MD 1061 ............................................................................................... 294 Picture 291: Spectrum of MD 1142 ............................................................................................... 295 Picture 292: Spectrum of MD 1280 with 75 Bd and 850 Hz shift.................................................. 295 Picture 293: Spectrum of a MFSK-8 signal ................................................................................... 296 Picture 294: Spectrum of a MFSK 16-signal ................................................................................. 296 Picture 295: AFS Navy modem FSK preamble .............................................................................. 297 Picture 296: Spectrum of South African Navy MFSK .................................................................... 297 Picture 297: Spectrum of MFSK BUL 8-Tone ............................................................................... 298 Picture 298: Spectrum ALCATEL 801 for 300 Bd ......................................................................... 298 Picture 299: Spectrum ALCATEL 801 for 150 Bd ......................................................................... 298 Picture 300: Spectrum of a TADIRAN modem .............................................................................. 299 Picture 301: Spectrum of TE-204 modem ...................................................................................... 300 Picture 302: Sonagram of a TE-204 modem ................................................................................. 300 Picture 303: Spectrum of TT2300-ARQ ......................................................................................... 301 Picture 304: Spectrum of the YUG 20 tone system ........................................................................ 301 Picture 305: Spectrum of a MIL STD 188-110A ser modem ......................................................... 302 Picture 306: Spectrum of 16 tone MIL STD 188-110A App A ....................................................... 303 Picture 307: Spectrum of MIL 188-110A 39 tone .......................................................................... 304 Picture 308: Data block structure used for MIL STD 188-110B ................................................... 305 Picture 309: Spectrum of a MIL STD 188-110 Appendix C in HDL mode .................................... 305 Picture 310: Spectrum of MIL STD 188-141A............................................................................... 307 Picture 311: Linking Protection in MIL STD 188-141A ................................................................ 308 Picture 312: Spectrum of MIL STD 188-342 ................................................................................. 311 Picture 313: Spectrum of a MLA Navy Baudot .............................................................................. 311 Picture 314: Bit pattern of a MLA Navy Baudot............................................................................ 312 

26

Picture 315: Spectrum of MT63 .................................................................................................... 313 Picture 316: Spectrum of Nokia burst system with 150.6 Bd ........................................................ 313 Picture 317: Spectrum of Nokia burst system with 301.7 Bd ........................................................ 313 Picture 318: Spectrum of Nokia burst system with 602.14 Bd ...................................................... 314 Picture 319: Spectrum of NUM 13 ................................................................................................ 314 Picture 320: Spectrum of an Olivia signal .................................................................................... 315 Picture 321: Oliva in the MFSK oscilloscope ............................................................................... 316 Picture 322: Spectrum of PACTOR I ............................................................................................ 318 Picture 323: Spectrum of PACTOR II ........................................................................................... 319 Picture 324: Spectrum of PACTOR II-FEC .................................................................................. 320 Picture 325: Spectrum PACTOR III speed level 1 ........................................................................ 322 Picture 326: PACTOR III speed level 2 ........................................................................................ 322 Picture 327: PACTOR III speed level 3 ........................................................................................ 322 Picture 328: PACTOR III speed level 5 ........................................................................................ 322 Picture 329: PACTOR III speed level 6 ........................................................................................ 323 Picture 330 Spectrum PACTOR IV on 1800 Hz ............................................................................ 324 Picture 331: Spectrum of a Packet Radio signal ........................................................................... 324 Picture 332: PANTHER-H synchronisation and frequency hops .................................................. 325 Picture 333: PANTHER-H synchronisation bursts ....................................................................... 326 Picture 334: PANTHER-H detailed view of one burst .................................................................. 326 Picture 335: Spectrum of PICCOLO MK VI ................................................................................. 330 Picture 336: Multi-channel Piccolo .............................................................................................. 331 Picture 337: Spectrum of PICCOLO 12 ........................................................................................ 332 Picture 338: Spectrum of a PSK31 signal ..................................................................................... 336 Picture 339: Phase plane of a BPSK PSK31 signal ...................................................................... 336 Picture 340: Spectrum of PSK 63 in QPSK mode ......................................................................... 337 Picture 341: Spectrum of PSK 125 in QPSK mode ....................................................................... 338 Picture 342: Phase plane of PSKAM 10/31/50 ............................................................................. 339 Picture 343: Spectrum of PSKAM 10 ............................................................................................ 339 Picture 344: Spectrum of PSKAM 31 ............................................................................................ 340 Picture 345: Spectrum of PSKAM 50 ............................................................................................ 340 Picture 346: Sonagram of Q15x25 ................................................................................................ 341 Picture 347: Oscilloscope display of RAC-ARQ ........................................................................... 342 Picture 348: Spectrogram of RFSM-2400 modem ........................................................................ 343 Picture 349: Spectrum of Robust Packet Radio ............................................................................ 344 Picture 350: Expanded spectrum of Robust Packet Radio ............................................................ 344 Picture 351: Spectrum of ROS ....................................................................................................... 345 Picture 352: Sonagram of ROS with pre-carrier .......................................................................... 345 Picture 353: Spectrum of ROU-FEC ............................................................................................. 346 Picture 354: Spectrum of RS-ARQ II ............................................................................................. 347 Picture 355: Frame structure of the HF Modem GM2100 ............................................................ 348 Picture 356: Spectrum of the HF Modem GM2100 ....................................................................... 348 Picture 357: Spectrum of RUS MIL voice scrambler with FSK lower/upper band ....................... 351 Picture 358: FSK oscilloscope of FSK carrier of the RUS MIL voice scrambler ......................... 351 Picture 359: Spectrum of Marconi 25tone .................................................................................... 352 

27

Picture 360: Spectrum and Sonagram of Marconi 25tone ............................................................ 352 Picture 361: Spectrum of Siemens CHX-200 modem .................................................................... 353 Picture 362: Spectrum of SITOR A .............................................................................................. 353 Picture 363: Timing of a SITOR A signal in the oscilloscope display ........................................... 354 Picture 364: Spectrum of SKYFAX ................................................................................................ 355 Picture 365: Spectrum of a SSTV transmission calling CQ ........................................................... 357 Picture 366: SSTV VIS code .......................................................................................................... 360 Picture 367: Sonogram of SSTV with VIS code ............................................................................. 360 Picture 368: Sonagram of STANAG 4197 ..................................................................................... 362 Picture 369: Spectrum of a STANAG 4202 .................................................................................... 363 Picture 370: Framing of a STANAG 4202 ..................................................................................... 364 Picture 371: Spectrum of a typical STANAG 4285 signal ............................................................. 365 Picture 372: Framing of a STANAG 4285 signal .......................................................................... 365 Picture 373: Spectrum of a STANAG 4415 signal ......................................................................... 366 Picture 374: STANAG 4479 over STANAG 4444 .......................................................................... 367 Picture 375: Spectrum of a STANAG 4481 FSK ............................................................................ 368 Picture 376: Spectrum of STANAG 4481 ....................................................................................... 368 Picture 377: Typical spectrum of a STANAG 4529 signal ............................................................ 369 Picture 378: Spectrum of STANAG 5031 with 75 bps and 42.5 Hz shift ....................................... 372 Picture 379: Spectrum of Systeme 3000 FEC mode ...................................................................... 373 Picture 380: Spectrum of TADIRAN AutoCall............................................................................... 374 Picture 381: Sonagram of TADIRAN AutoCall ............................................................................. 374 Picture 382: Spectrum of a Tadiran signal .................................................................................... 374 Picture 383: Spectrum with Sonagram .......................................................................................... 375 Picture 384: Spectrum of a TFM3 signal ....................................................................................... 375 Picture 385: Spectrum of a TFM5 signal ....................................................................................... 375 Picture 386: Spectrum Thales voice scrambler ............................................................................. 376 Picture 387: Sonagram of Thales voice scrambler ........................................................................ 376 Picture 388: Typical Spectrum of Throb ........................................................................................ 377 Picture 389: Spectrum of TMS-430 modem ................................................................................... 377 Picture 390: Spectrum of a typical Twinplex signal ...................................................................... 379 Picture 391: Typical spectrum of a VFT signal ............................................................................. 381 Picture 392: Spectrum of VISEL .................................................................................................... 382 Picture 393: VISEL bit correlation ................................................................................................ 382 Picture 394: Spectrum of a WINMOR 4FSK ................................................................................. 383 Picture 395: Sonagram of a WINMOR 4FSK with CW ID ............................................................ 384 Picture 396: Spectrum od the AMSS carrier ................................................................................. 386 Picture 397: AMSS measurement of the baudrate ......................................................................... 386 Picture 398: Phase constellation of the AMSS signal .................................................................... 387 Picture 399: Spectrogram of single letter beacons ........................................................................ 391 Picture 400: Spectrum of CRY-2001 FSK ...................................................................................... 393 Picture 401: Sonagram of CRY-2001 ............................................................................................ 393 Picture 402: Spectrum of a MK III buoy........................................................................................ 394 Picture 403: Oscilloscope display of a MK III .............................................................................. 395 Picture 404: Auto correlation function of a MK III ....................................................................... 395 

28

Picture 405 : Typical track of a chirpsounder ............................................................................... 395 Picture 406: Typical spektrum of a CODAR signal ...................................................................... 398 Picture 407: Oscilloscope display of a typical CODAR signal ..................................................... 398 Picture 408: Spectrum of a Datatrak signal .................................................................................. 399 Picture 409: Spectrum of a Digisonde 4D ..................................................................................... 401 Picture 410: Chip sequence of a Digisonde 4D ............................................................................ 401 Picture 411: Spectrum of an EFR signal ....................................................................................... 402 Picture 412: Function of an Ocean Radar .................................................................................... 405 Picture 413: Transmission of LORAN-C ....................................................................................... 405 Picture 414: Spectrum of the MF radar at Juliusruh .................................................................... 408 Picture 415: Puls repetition time of the MF radar at Juliusruh ................................................... 408 Picture 416: Spectrum of a NAVTEX signal .................................................................................. 409 Picture 417: Spectrum of an OFDM ............................................................................................. 411 Picture 418: Spectrum of 48 x 48 OFDM NBTV ........................................................................... 413 Picture 419: Spectrum of 96 x 72 OFDM NBTV ........................................................................... 414 Picture 420: Spectrum of digital NBTV ........................................................................................ 414 Picture 421: Phase plane of digital NBTV .................................................................................... 415 Picture 422: Framing of digital NBTV .......................................................................................... 416 Picture 423: Baudrate measurement of digital NBTV ................................................................... 416 Picture 424: Spectrum of Hybrid NBTV ........................................................................................ 420 Picture 425: Sonagram of Hybrid NDTV ...................................................................................... 420 Picture 426: Spectrum of a BCPSK signal of NDS200 DGPS ...................................................... 421 Picture 427: Phase spectrum of NDS200 DGPS signal with 100 Bd peaks .................................. 422 Picture 428: Phase plane of NDS200 DGPS signal ...................................................................... 422 Picture 429: Over the horizon radar (OTHR) ............................................................................... 423 Picture 430: French OTHR with 25ms pulses or 40 pulses per second (pps) ............................... 424 Picture 431: CIS OTHR ABM-2 with 100ms pulses or 10 pps ...................................................... 424 Picture 432: Cyprus OTHR with 20ms pulses or 50 pps ............................................................... 424 Picture 433: IRAN OTHR with 30ms pulses or 33 pps ................................................................. 424 Picture 434: OTHR SuperDARN with 25ms or 40 pps .................................................................. 424 Picture 435: Chirp OTHR with 20ms or 50 pps ............................................................................ 424 Picture 436: HF spectrum around 13.560 MHz ............................................................................ 425 Picture 437: Audio spectrum of RFID tags ................................................................................... 425 Picture 438: Pulses of RFID tags .................................................................................................. 426 Picture 439: Spectrum and sonagram of a BRAS signal ............................................................... 427 Picture 440: Timing of the BRAS system ....................................................................................... 428 Picture 441: Timing of the RS-10 system ...................................................................................... 428 Picture 442: BRAS-3/RS-10 burst sequence master ...................................................................... 429 Picture 443: BRAS-3/RS-10 burst sequence slave ......................................................................... 429 Picture 444: Spectrum of a SuperDARN ....................................................................................... 431 Picture 445: Sonagram of a 7s operation of SuperDARN ............................................................. 432 Picture 446: Pulse sequence of a SuperDARN .............................................................................. 432 Picture 447: Frequency sweep of a FMCW signal ........................................................................ 435 Picture 448: Function of a wave radar ......................................................................................... 435 

29

2 List of Tables

Table 1: C4FM symbol table ........................................................................................................... 49 Table 2: Bit value for QPSK ............................................................................................................ 55 Table 3: Phase shifts for CQPSK ..................................................................................................... 57 Table 4: Bit values for DQPSK ........................................................................................................ 59 Table 5: Bit values for QAM ............................................................................................................ 60 Table 6: Different description for data levels .................................................................................. 68 Table 7: Code table for ITA2, ITA2P and ITA3 ............................................................................... 82 Table 8: Russian MTK2 alphabet .................................................................................................... 83 Table 9: Code table for CCIR476-4, HNG-FEC and PICCOLO MK VI alphabetsITA 2 ............... 84 Table 10: ASCII table ...................................................................................................................... 88 Table 11: CCIR 493 alphabet .......................................................................................................... 90 Table 12: X.25 Packet frame ......................................................................................................... 102 Table 13: Common used transmission modes ................................................................................ 113 Table 14: Terms and their description ........................................................................................... 114 Table 15: Determination of necessary bandwidths for emissions ................................................. 122 Table 16: Table of waveforms and possible user sorted by Baud rate .......................................... 135 Table 17: ALE 3G call types .......................................................................................................... 141 Table 18: Tone layout for ALE400 ................................................................................................ 142 Table 19: ARQ-S repetition cycle .................................................................................................. 149 Table 20: ARQ-SWE repetition cycle ............................................................................................. 150 Table 21: BR6028 channel frequencies ......................................................................................... 160 Table 22: BR6029C channel frequencies ....................................................................................... 162 Table 23: Tone layout for the 500 Hz variant ................................................................................ 164 Table 24: Tone layout for the 400 Hz variant ................................................................................ 164 Table 25: Tone layout of CHN MIL 8FSK ..................................................................................... 166 Table 26: Tone layout CHN hybrid modem 4FSK-OFDM20 ........................................................ 168 Table 27: Tone layout of the CHN hybrid modem ......................................................................... 169 Table 28: Frequencies of the Chinese 4+4 modem ....................................................................... 172 Table 29: Tone layout CIS VFT 3 channels 100 bd ....................................................................... 198 Table 30: CLOVER-II tone frequencies ......................................................................................... 202 Table 31: CLOVER-II modulation modes ...................................................................................... 203 Table 32: CLOVER 2000 Modulation formats .............................................................................. 205 Table 33: Clover 2000 modes and data rates ................................................................................ 206 Table 34: CLOVER 2500 tone frequencies .................................................................................... 206 Table 35: CLOVER 2500 Modulation ........................................................................................... 207 Table 36: CODAN tone frequencies .............................................................................................. 208 Table 37: Tone frequencies for CODAN 12 channel mode ........................................................... 209 Table 38: Most common modes of Contestia ................................................................................. 211 Table 39: Coquelet tone frequencies ............................................................................................. 213 Table 40: Coquelet tone frequencies ............................................................................................. 214 Table 41: Frequencies used by Coquelet ....................................................................................... 215 Table 42: Crowd 36 control sequences.......................................................................................... 216 Table 43: Morse alphabet .............................................................................................................. 219 

30

Table 44: Data structure of DGPS ................................................................................................ 220 Table 45: PRC Message Broadcast Parameters ........................................................................... 222 Table 46: DominoEX waveforms ................................................................................................... 225 Table 47: DRM OFDM parameter ................................................................................................ 232 Table 48: DRM OFDM number of carriers .................................................................................. 232 Table 49: Number of carrier for WinDRM .................................................................................... 235 Table 50: Data rates of WinDRM .................................................................................................. 235 Table 50: Controll codes DUP-ARQ ............................................................................................. 237 Table 51: Abbreviations in FAX transmissions ............................................................................. 245 Table 52: Geographical letter groups ........................................................................................... 245 Table 53: ID's of Globe Wireless coast stations ............................................................................ 248 Table 54: Used HFDL frequencies sorted by ID ........................................................................... 264 Table 55: Ground stations using HFDL identified by ID .............................................................. 264 Table 56: Annex 10 Audio frequencies .......................................................................................... 266 Table 57: Tone layout for Japan 8-tone ASK ................................................................................ 275 Table 58: Tone layout of Japan 32-tone OFDM modem ............................................................... 278 Table 59: JT65 tone separation for the modes A/B/C ................................................................... 282 Table 60: LINK 11 frequencies ..................................................................................................... 285 Table 61: Tone table for MD 1061 ................................................................................................ 294 Table 62: Tone table for MD 1142 ................................................................................................ 294 Table 63: Frequencies of MFSK-16 .............................................................................................. 296 Table 64: MIL STD 188-110A ser data rate versus FEC .............................................................. 302 Table 65: Tone layout Mil 188-110A 16 tone ................................................................................ 303 Table 66: Tone layout Mil 188-110A 16 tone variant ................................................................... 303 Table 67: Modulation types used for MIL STD 110B Appendix C ................................................ 304 Table 68: Baud rates of MIL 188-110C Appendix D .................................................................... 306 Table 69: Table of ALE tone frequencies ...................................................................................... 307 Table 70: Waveforms of ALE 3G ................................................................................................... 310 Table 71: Tone layout MIL STD 188-342 ..................................................................................... 311 Table 72: MT 63 transmission modes ............................................................................................ 312 Table 73: Most common modes of Olivia ...................................................................................... 315 Table 74: Different PACTOR I modes ........................................................................................... 318 Table 75: PACTOR II modes ......................................................................................................... 319 Table 76: PACTOR III speed levels .............................................................................................. 321 Table 77: PACTOR III relation between speed level and used tones ............................................ 321 Table 78: Speed levels of PACTOR VI .......................................................................................... 323 Table 79: Tone frequencies for Piccolo 6/12 ................................................................................ 328 Table 80: Character/tone combination ......................................................................................... 329 Table 81: Character/tone combination for inverted mode ............................................................ 330 Table 82: Character/tone combination for PICOOLO 12 ............................................................ 333 Table 83: PSK10 character set ...................................................................................................... 335 Table 84: GM2100 transmission modes ........................................................................................ 348 Table 85: Most common modes of RTTYM ................................................................................... 350 Table 86: SSTV tones used ............................................................................................................ 357 Table 87: Different SSTV modes ................................................................................................... 359 

31

Table 88: Tone layout STANAG 4197 16 tone part ....................................................................... 361 Table 89: Tone layout STANAG 4197 39 tone part ....................................................................... 362 Table 90: STANAG 4285 transmission modes ............................................................................... 364 Table 91: LPC10 2400 bps and 800 bps parameters .................................................................... 367 Table 92: STANAG 4529 transmission modes ............................................................................... 369 Table 93: Waveforms of STANAG 4538 ........................................................................................ 370 Table 94: TWINPLEX modes ......................................................................................................... 378 Table 95: TWINPLEX shift modes ................................................................................................. 379 Table 96: Typical parameters for VFT .......................................................................................... 380 Table 97: Centre frequencies in different VFT systems ................................................................. 381 Table 98: Transmission slots of the amateur radio beacon system ............................................... 390 Table 99: Schedule for the amateur radio beacon system ............................................................. 390 Table 100: Russian single letter beacons ...................................................................................... 392 Table 101: Typical cluster of single letter beacons ....................................................................... 392 Table 102: Known Datatrak systems and their frequencies .......................................................... 400 Table 103: Byte structure of the EFR signal .................................................................................. 402 Table 104: EUROFIX modulation pattern combination ................................................................ 403 Table 105: LORAN chains and their identification numbers ......................................................... 406 Table 106: LORAN Data Channel message components .............................................................. 407 Table 107: NAVTEX identification letters ..................................................................................... 409 Table 108: Structure of a NAVTEX message ................................................................................. 409 Table 109: OFDM NBTV modes .................................................................................................... 412 Table 110: Modes of digital NBTV ................................................................................................ 418 Table 111: Frequencies for NDS200 DGPS system ...................................................................... 421 Table 112: Frequencies of the RSDN 20 system ............................................................................ 426 Table 113: Frequency setup of the BRAS system for one chain („Semba“) .................................. 428 Table 114: Location of SuperDARN transmitter ........................................................................... 430 Table 115: Active time signal stations ........................................................................................... 433 Table 116: Parameter of the WERA system ................................................................................... 434 Table 117: International callsigns ................................................................................................. 441 Table 118: Country codes .............................................................................................................. 445 Table 119: Translation of a four digit SELCALL number ............................................................. 446 Table 120: Translation of a five digit SELCALL number .............................................................. 447 Table 121: Coast station identification numbers by blocks and countries .................................... 449 Table 122: Allocation of MID's ..................................................................................................... 454 Table 123: NATO routing indicators ............................................................................................. 456 Table 124: List circuits and their routing indicators ..................................................................... 459 Table 125: Circuits in the AFTN .................................................................................................... 463 Table 126: Priority levels in AFTN messages ................................................................................ 464 Table 127: Table of AFTN message contents ................................................................................ 465 Table 128: Letter groups in NOTAM messagesWeather Forecast (TAF and METAR) ................. 472 Table 129: Description of METAR groups .................................................................................... 475 Table 130: Teleprinter Alphabets for Comparison ........................................................................ 476 Table 131: Q-codes ........................................................................................................................ 493 Table 132: X-codes ........................................................................................................................ 494 

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Table 133: Z-codes ........................................................................................................................ 504 Table 134: Abbreviations .............................................................................................................. 513 

33

3 Removed Signals

There are some modulations and systeme which ar not used anymore. To keep the number of pages in a useable range, those signals are deleted where the probabilty is very high that they never will be active on shortwave. At the moment these are the following signals:

ALF (2013) DECCA (2013) OMEGA (2013) D-OMEGA (2013)

This list will grow with the next editions. In brackets you will find the year of removment.

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35

4 General

For years shortwave radio has been used for communication beyond the line of sight. With the introduction of world wide satellite services in the geostationary or low earth orbits HF radio communication lost more and more in interest. But with the introduction of new, sophisticated modems and digital broadcast services in high quality HF communication has seen a renewal during the last years. Shortwave radio, however, has some qualities that will ensure its attractiveness for some time. The most important one for commercial users is that there is no charge for using the ionosphere. In the military context this translates to low cost, potentially global communication that has the important attributes of national ownership and military control. And in comparison to satellite services shortwave communication is harder to disrupt. The good old radio for shortwave has been perfected during the last years in several ways. Information data rates of a few tens of bits per second were increased to more than 19200 bit/s by sophisticated modem techniques and error correction. Algorithms were created to adapt transmission parameters to channel quality or initiate a change to a better channel. Passive and active channel analysis, i.e. sending and measuring test signals on assigned pool frequencies have been developed to solve problems of channel distortions. For example an automatic link setup (ALE) according to an international standard is performed with a flexible address pattern. Automation guarantees a link setup whenever a useful frequency is found in the pool. TCP/IP is the most widely used network protocol and supported by the majority of computers and software. This international standard ensures interoperability of very different platforms or operating systems. Most equipment for shortwave like modems and radios are able to interface with local networks by LAN. Even conversions form ISDN networks, GSM, PSTN and others are possible. New developments are expected which will enhance the capabilities of transmission protocols and modem technology for higher transmission speed. Using wider bandwidths will also achieve higher data rates. By intensifying the modulation/coding higher data rates and throughputs are possible. With modern processor technology the adaptation of transmission parameters to the channel conditions will give a higher quality for the exchange of information via shortwave. All these circumstances will present old modes with improvements but mainly new modes with their unique sound to the shortwave listener. This book has been written to help the listener on shortwave in identifying the different modes or waveforms which are active throughout the shortwave band. It will never be complete. New waveforms are heard nearly every month. Due to the sophisticated possibilities of modern modems the signal analyses becomes more and more very difficult.

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But this book will give a good overview which techniques are state of the art today. It has to be mentioned that most of the pictures were produced with the decoder CODE 300-32 by HOKA, but some pictures are made with the PROCEED decoder by PROCITEC GmbH. This book is divided in four main parts:

Basic information Waveforms used on shortwave Tables to help identifying stations or circuits on shortwave Abbreviations and Index

The first part basic information is giving an overview about common modulation techniques with a short description and how they look like in the spectrum or phase plane display. This part also describes standard expressions from the field of coding, error correction and so on which are often used in the field of radio communication. The following section describes most of the waveforms which can be heard on shortwave. Where ever possible the waveform is described with it’s main parameter. If there is any further information available like framing, coding aso. these are also described. The next part is showing some tables and description which are useful for identifying stations or circuits. The book finishes with the abbreviation table and the index. In comparison to the previous version the descriptions of waveforms used on VHF/UHF has been moved to a second book called “Technical Handbook for Radio Monitoring VHF/UHF”. This step was necessary because the number of pages was increasing above 800 which is very difficult to handle.

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6 HF Modes

The following part of the “Technical Handbook” describes waveforms in different depths. Wherever possible the different waveforms are described and enriched by spectrum, phase plane or oscilloscope pictures. On top of the page is written the used name. Below the name is also mentioned other known names for the same waveform. General Information In the following descriptions there are different sort of illustrations for the described waveforms. Wherever possible the spectrum is shown. But there are also pictures for phase constellations, correlation functions, sonagram and so on. These different type of pictures are described in the following part. Spectrum The spectrum display is showing the audio frequency range from 0 Hz to 5500 Hz (sometimes a larger bandwidth with 11 kHz or 22 kHz is used). The spectrum is the result of a Fast Fourier Transformation (FFT) calculated on the samples of the used audio card. Sonagram The sonagram view displays the relation between frequency, time and amplitude of a signal. One axis shows the frequency similar to the spectrum display, the second axis the time. The amplitude of the signal is displayed in the colour of the signal. Oscilloscope The oscilloscope display is showing the amplitude behaviour of a signal either as direct audio signal or the constellation after demodulation of the signal. For FSK or MFSK signals in the vertical domain the audio frequency is shown instead of the amplitude of a signal. Phase Spectrum For determination of the speed of a PSK signal the phase spectrum is used. Without any zoom the display is similar to the normal spectrum view. Because PSK signals very often also produce a n amplitude modulation with a peak at the symbol rate. By zooming into the spectrum these peaks can be determined and allow the measurement of the symbol rate.

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Phase Plane This display is also sometimes called a vector scope. It displays any frequency or phase modulation as a rotary vector. The phase plane is used to show the phase constellation of phase modulated signals. Speed Bit Analyses This function is similar to a FAX display. The bit information is displayed as a line with black for a 1 and nothing for a 0. With the correct baud rate patterns in the bit stream can be recognized. Bit Correlation, Autocorrelation Function (ACF) The Autocorrelation Function is used to analyse the repetition of bit pattern in a bit stream. If these repetition are constant the ACF will show a peak at a value related to the length of bit pattern with is repeated. These values can range from 2 over 7.5 (like in Baudot with 1.5 stop bit), 11 (like in a ASCII transmission with 1 start, 1 stop and 1 parity bit , up to i.e. 64 for STANAG 4529. The ACF value is very specific for various modes.

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1. AFS Navy FSK

This FSK modem is using a baud rate of 130.36 Bd and a shift of 700 Hz. Traffic is always encrypted. The modem is in use of the AFS navy. The spectrum is shown in the following picture:

Picture 58: Spectrum of an AFS navy modem

2. ALE 3G

STANAG 4538, MIL STD 188-110A, MIL STD 188-141B App. C ALE 3G is the third generation of automatic link establishment. It is based on the MIL STD 188-110 with a centre frequency of 1800 Hz and a symbol rate of 2400 Bd. ALE 3G has a burst length of 613.33 ms or 1472 PSK symbols. The payload is always 26 bit. The preamble has a length of 160 ms or 384 PSK symbols. The modulation is 8PSK. The following spectrum shows an ALE 3G.

Picture 59: Spectrum of an ALE 3G

The typical phase constellation of a 8PSK is as following:

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Picture 60: Phase constellation of an ALE 3G 8PSK signal

ALE 3G has the possibility to work in an asynchronous mode as ALE 2G but achieves the best performance with a synchronous mode. In the synchronous mode a fixed structure for transmissions and listening to a channel is used. Each so called dwell structure has a length of 4 seconds. The timing is divided into 5 different slots with 800ms each. The next figure shows the dwell structure of an ALE 3G.

Picture 61: Dwell structure of an ALE 3G

Each dwell period starts with a listen slot where the modem tries to detect traffic in the specific channel. This listen slot is followed by the calling slots which are used for exchanging protocol data units (PDU). The PDU has a length of 613 ms and allows 70 ms for propagation delay and 100 ms for synchronisation uncertainty. If a calling station detects a handshake PDU it will stop its own call. If the channels are free it will call in a slot and will listen to a handshake PDU in the next slot. The following picture shows the different PDU’s which are used in an ALE 3G:

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Picture 62: ALE 3G protocol data units

During the call a 3 bit call type is used. These types are listed in the following table.

Call Type Description Packet Data Traffic will use the ALE 3G protocol,

negative SNR is ok HF Modem Circuit Traffic will use an HF data modem.

Needs positive SNR Voice Circuit Order wire voice traffic. Needs SNR

> 10 to 15 dB High-Quality Circuit Traffic needs higher SNR than order

wire Unicast One-to-one call, caller will designate

the traffic channel Multicast One-to-many call, caller will

designate the traffic channel Link release Caller announces release of called

station (or stations) and the traffic channel

Table 17: ALE 3G call types

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3. ALE400

Automatic Link Setup ALE400 is an 8FSK waveform for automatic link establishment developed by Patrick Lindecker F6CTE derived from the MIL STD 188-141A with a narrow bandwidth of 400 Hz so that this mode can be used in 500 Hz channels. It has exactly the same functions as the standard ALE. The baud rate was reduced to 50 Bd. The tone distance between carriers is 50 Hz. Related to a centre frequency of 1625 Hz this gives the following tone layout:

Tone Number

1 2 3 4 5 6 7 8

Frequency in Hz

1450 1500 1550 1600 1650 1700 1750 1800

Binary Value

000 001 011 010 110 111 101 100

Table 18: Tone layout for ALE400

Picture 63: Spectrum of ALE400

Picture 64: Expanded spectrum of ALE400

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4. ALIS

Automatic Link Setup ALIS is the automatic link processor and frequency management system used by all Rhode & Schwarz modems besides ALE. ALIS is using narrowband FSK with 228.66 Bd and a shift of 170 Hz.

Picture 65: Spectrum of an ALIS signal

With the ALIS software selected for the Data Link Processor R&S GS2200, the following functions are automatically handled by the processor:

Continuous passive channel analysis of all pool frequencies during scanning mode Channel selection by means of computation of the optimum working frequency from a pool

of frequencies Reliable and fast link setup at the optimum available frequency Selective calling addresses (up to 9999) Automatic transmission of status

o Type of modulation o Speed of data transmission o Type of data protection (FEC, ARQ, PRP)

Automatic error correction (ARQ or PRP) and adaptive response during message transmission, either at a data rate of 228.66 Bd (normal FSK modulation, basic feature) or with additional HF data modem up to 5400 bit/s

Data transmission format o 5 bit Baudot (telex) o 7 bit ASCII (text files from PCs) o 8 bit ASCII (text and binary files etc)

Message length: unlimited

Depending on the requirements: o Preferred or existing method o Link setup with or without adaptive response o Response to interference on the radio link (ARQ) o Frequency economy, spectrum pollution and probability of intercept considerations o Operator convenience, error correction and expandability o Interoperability with legacy systems and those of other manufacturers

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The following sonagram shows the typical link set up procedure of the R & S –ALIS:

Picture 66: Sonagram ALIS link setup procedure

5. ALIS 2

Improved Automatic Link Setup ALIS 2 is a burst 8 tones MFSK ARQ system made by Rohde & Schwarz with a standard speed of 240 Bd (equivalent to 720 bit/s). Shift between tones is 240 Hz, and the tone duration is 4.15254 ms. A preamble which contains an identification code and has a length of 21 bits. The transmission block consists of 55 tri-bits, resulting in 165 bits per frame. A 16 bit CRC checksum is used. The system can use either 5 bits ITA2 or 8 bits ASCII ITA5 alphabet.

Picture 67: Spectrum of ALIS 2

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6. ARD9800 OFDM 36ch Modem

ARD9800 This modem developed by AOR is using OFDM as modulation method. The OFDM is using 36 carriers in the range from 300 Hz - 2500 Hz. The symbol rate of each carrier is 50 Bd with a guard interval of 4 ms. The spacing between the carriers is 62.5 Hz. Each carrier is DQPSK modulated. The error correction for voice is Golay & Hamming, for video/data Convolution & Reed-Solomon. Each transmission starts with a header of 1 sec and consists of 3 tones and a BPSK training pattern for synchronization. For digital voice the AMBE2020 coder and decoder are used.

Picture 68: Spectrum of ARD9800-OFDM

Picture 69: Spectrum and Sonagram of ARD9800-OFDM

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7. ARQ-E

ARQ-N, ARQ-1000 duplex ARQ-E is a synchronous duplex ARQ with the 2 stations on different frequencies. It is using the 7 bit ITA 2-P alphabet with 4, 5 or 8 character repetition cycle, inverting every 4th, 5th or 8th character. In the ARQ-N system all characters are erect. ARQ-N is mainly heard with 96 Bd.

Picture 70: Spectrum of an ARQ-E signal with 288 Bd

ARQ-E and ARQ-N are operating in duplex mode with baud rates of 48, 50, 64, 72, 96, 144, 184.6, 192 and 288 Bd.

8. ARQ-E3

CCIR 519 Variant, TDM 342 1 Channel ARQ-E3 is a synchronous duplex ARQ using the 7 bit error correcting ITA 3 alphabet with repetition cycle of 4 or 8 characters. Two stations are working on different frequencies as Master and Slave stations. If another faulty code than the 35 combinations of the allowed alphabet is received a repetition request is initiated. The RQ signal is initiating the retransmission. All characters are checked within one repetition cycle, an error signal is triggering another repetition process immediately until all signals are received correctly. In a standard repetition cycle of 4 characters one RQ and three repeated characters and in a repetition cycle of 8 characters one RQ and 7 repeated characters are transmitted.

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Picture 71: Spectrum of ARQ-E3 in idle mode

Note: In idle mode ARQ-E3 is often detected as FEC 100! ARQ-E3 is operating in duplex mode with baud rates of 48, 50, 96, 192 and 288 Bd.

Picture 72: ARQ-E3 – Signal Structure

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9. ARQ-M2

TDM 242, TDM 342, CCIR 242, CCIR 342, ARQ-28 ARQ-M2 CCIR 242 is a synchronous duplex ARQ system using the 7 bit error correcting ITA 3 alphabet consisting of two or four channels in time division multiplex in a single radio channel. The two stations use different frequencies for full duplex operation. The 2 channel system is simply made from interleaving erect characters for channel A and inverted characters for channel B, i.e. A, -B, A, -B, A, -B, A, -B etc. ARQ - M2 is used on fixed lines between two stations. Due to their automatic transmission they often have long idling periods in which no information is transmitted. These periods can be recognized by a typical rhythm on the signal. If there is any information transmitted this rhythm is not audible. The main baud rate is 96 and 200 Bd.

10. ARQ-M4

TDM 242, TDM 342, CCIR 242, CCIR 342-2, ARQ-56 ARQ – M4 CCIR 342 is a synchronous duplex ARQ, which uses the ITA 3 alphabet 7 bit. Two or four channels in TDM (time division multiplex) are possible. Two stations are working on different frequencies, working as ISS (transmitting) and IRS (receiving) station. At start of a cycle the first characters of all channels are inverted; 1 channel: A-channel erect 2 channel: A-channel erect, B-channel inverted, character interleaved. 4 channel: A-channel erect, B-channel inverted, C-channel inverted, D-channel erect Channels A and B character interleaved, A/B and C/D bit interleaved. Marked cycles of 4 and 8 characters. ARQ–M4 is used on fixed lines between two stations. Due to their automatic transmission they often have long idling periods in which no information is transmitted. These periods can be recognized by a typical rhythm on the signal. If there is any information transmitted this rhythm is not audible.

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Picture 73: Typical spectrum of an ARQ-M4

This system was mainly heard with 192 Bd.

11. ARQ-S

ARQ 1000-S, Siemens ARQ 1000 ARQ-S is a synchronous simplex ARQ using the 7 bit error correcting ITA 3 alphabet with the addition of 1 bit for parity-check. The receiving station is checking the 3:4 ratio of the ITA 3 code. If the pulse polarity is not corresponding to this ratio, an automatically repetition is initiated. The additional parity of 1 bit is reducing the error rate. The receiving station is transmitting an acknowledgement signal RQ if the character block is received correctly and requests the next block. If the received block contains errors a repetition is requested. If the acknowledgement signal is not received correctly, a special character for retransmission is transmitted. Two stations use the same frequency, working as ISS (transmitting) and IRS (receiving) stations. For automatic setting - up selective calling is possible also FEC operation with error correction in time diversity mode for broadcast transmissions. Every odd numbered cycle has all bits inverted. Repetition cycle timings for block lengths of 3, 4, 5, 6 or 7 characters are as follows:

Cycle Characters Transmission Pause 438 ms 3 characters at 7 bits 219 ms 219 ms 583 ms 4 characters at 7 bits 292 ms 292 ms 729 ms 5 characters at 7 bits 365 ms 365 ms 875 ms 6 characters at 7 bits 438 ms 438 ms 1021 ms 7 characters at 7 bits 510 ms 510 ms

Table 19: ARQ-S repetition cycle

For FEC operation every message is transmitted twice in a time diversity procedure. After a space of 15 characters the first transmission is repeated. If a character block is received with errors, the system is waiting for the second transmission to print the correct information. If this is also not possible this character is replaced by a blank space.

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12. ARQ-SWE

SWED ARQ, CCIR 518 Variant ARQ-SWE is a synchronous simplex ARQ using the error correcting 7 bit ITA 3 alphabet with one extra bit for parity checking. Two stations use the same frequency, working as ISS (transmitting) and IRS (receiving) stations. Every odd cycle has all the bits inverted. According to the quality of the radio link SW ARQ can change the block length between 3, 9 or 22 characters. A block length of 3 characters is identical to SITOR A. The repetition cycle is as follows:

Cycle Characters Transmission Pause

450 ms 3 characters at 7 bits 210 ms 210 ms

900 ms 9 characters at 7 bits 630 ms 270 ms

1800 ms 22 characters at 7 bits 1540 ms 260 ms

Table 20: ARQ-SWE repetition cycle

SW ARQ is normally using 100 Bd and a shift of typical 400 Hz. This system, based on normal SITOR, was used by the Ministry of Foreign Affairs (MFA) of Sweden. A similar ARQ was used by the MFA of Norway but without changing the character cycle.

Picture 74: Spectrum of ARQ-SWE

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13. ARQ 6-70S

CCIR 518 variant S ARQ 6-70 is a synchronous simplex ARQ using the 7 bit error correcting ITA3 alphabet with two stations (usually) on the same frequency, one of them called the ISS (transmitting), the other the IRS (receiving) station. Complete repetition cycle is as follows: ARQ 6-70: 350 ms: 6 characters at 35 ms = 210 ms with 140 ms pause. ARQ 6-70 is working with 200 Bd.

14. ARQ 6-90/98

CCIR 518 variant SITOR ARQ 6-90/98 is a synchronous simplex ARQ using the 7 bit error correcting CCIR 476 alphabet with two stations (usually) on the same frequency, one of them called the ISS (transmitting), the other the IRS (receiving) station. Each transmitted block contains 6 characters or 42 bit. Complete repetition cycle is as follows: ARQ 6-90: 450 ms: 6 characters at 35 ms = 210 ms with 240 ms pause. ARQ 6-98: 490 ms: 6 characters at 35 ms = 210 ms with 280 ms pause. ARQ 6-90/98 is working with 200 Bd.

Picture 75: Spectrum of an ARQ 6-90

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Picture 76: Oscilloscope display of ARQ 6-90

15. ASCII

IRA-ARQ ITA No.5 ASCII is a continuous asynchronous signal with 1 start bit, 5, 6, or 7 data bits and optional a parity bit and 1 stop bit. A character can consist of total 8, 9 and 10 bits. Parity can be none odd or even. This system implements the parity check which means that one bit (parity bit) is added at the end for error detection. The number of 1s is checked and if an odd number is found and parity has been defined as ODD, then the parity bit should be 1, otherwise an error has occurred. If parity has been defined as EVEN and an even number of 1s is found, then the parity bit should also be 1.

16. AUM-13

AUM-13 is a MFSK which is transmitting numeric codes with a data rate of 8 Bd. This mode uses 10 tones for the transmission of the numbers 0…9 and 3 tones for message handling. On tone is assigned as idle, one for the space and one for repetition. The transmission starts with a sequence transmitted with 1Bd and is changing to 8 Bd for the data. The total bandwidth is 480 Hz. The modulation is AM. This slow speed allows an exchange of information even under poor conditions and multipath propagation with fading.

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Picture 77: Spectrum of AUM 13 signal

17. AUS MIL ISB Modem

This ISB modem is in used of the Australian forces. It is using the upper and lower sideband with different signals and modulation. In the upper sideband is transmitted a 50 Bd signal with 340 Hz shift and in the lower sideband a 600 Bd signal with 600 Hz shift. Both modems are encrypted with no apparent ACF.

Picture 78: Spectrum of the AUS MIL ISB modem with both waveforms

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Picture 79: Spectrum of the 50 Bd waveform

Picture 80: Spectrum of the 600 Bd waveform

18. AUTOSPEC

AUTOSPEC with Spread 11, Spread 21, Spread 51 AUTOSPEC is a synchronous FEC system that converts the 7 1/2 unit ITA-2 code into 10 element error detectable characters. It is used in one way or two way radio links. Single bit errors are corrected. The original Mark I was 0 interleave, MK II introduced 10 (the 'norm'), 20 and 50 character interleave. The system operates at 68.5 Bps for 50 Bd input and 102.75 Bps for 75 Bd input.

Picture 81: Spectrum of AUTOSPEC with 75 Bd

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Contestia 8-1000 mode:

Picture 181:: Spectrum and sonagram of Contestia 8-1000 mode

Contestia 32-1000 mode:

Picture 182:: Spectrum and sonagram of Contestia 32-1000 mode

73. Coquelet 8

Coquelet 8 is a French designed system based on sending 2 audio tones, in sequence from a selection of 8 for each of the different characters to be sent. Idle /standby condition is between tones 4 and 5.

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The tones used have a space of 27 Hz for the 13.3 Bd system and 26.7 Hz for the 26.67 Bd system. Both are grouped in 2 tone groups.

Tuning

Spectrum Analyzer full scale

Transmission start Only one tone present

Idle conditions Only the first and the last tone are present

Transmission: All eight tones are present

Picture 183: Example of Coquelet-8 decoding

Tone assignment

Group 1 Group 2

1 2 3 4 5 6 7 8 9 10 11 12 773 800 826 853 880 907 933 960 880 907 933 960

Table 39: Coquelet tone frequencies

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Picture 184: MFSK Coquelet-8 signal

74. Coquelet 8 FEC

Coquelet 80 Coquelet 8 FEC is a synchronous system with error correction. Similar to Coquelet 8 the system is using two tones assigned to two groups but with slightly different frequencies. The FEC is done by transmitting every character twice with a specific time between both transmissions. The second character has a different format caused by mathematical operations. Tone assignment:

Group 1 Group 2 1 2 3 4 5 6 7 8 1 5 6 7 8

773 800 827 853 880 907 935 960 773 880 907 935 960

Table 40: Coquelet tone frequencies

75. Coquelet 100

MFSK Modem ALCATEL 810 This robust waveform uses 8 tones which are modulated with different speeds of 16.7 and 100 Bd. The tone spacing is 100 Hz.

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Picture 185: Spectrum of Coquelet 100 with 16.7 Bd

76. Coquelet 13

Coquelet MK1, French Multitone Coquelet 13 is a French designed system based on sending 2 audio tones, each 75 ms, in sequence from a selection of 12 for each of the different characters to be sent. Idle /standby condition is tone 0. This tone 0 is between the two centre tones 8 and 9, thus making tuning easy when the station is in standby/ idling. The baud rate transmitted is 13.33 Bd and 20 Bd. Tones used are No. 1 to 8 at 30 Hz apart for group I and tones No. 9 to 13 at 30 Hz apart for group II. Coquelet is using the ITA 2 characters. They are converted into tones by the following table:

Tone number Frequency in Hz

Bit 1 Bit 2 Bit 3 Bit 4 Bit 5

1 812 1 1 1 2 842 1 1 3 872 1 4 902 1 5 932 1 1 6 962 1 1 7 992 1 8 1022

0 (idle tone) 1052 9 1082 1 1

10 1112 1 11 1142 1 12 1172

Table 41: Frequencies used by Coquelet

The two tones are selected from each frequency group for the transmitted characters.

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Picture 186: Spectrum of Coquelet 13

77. CROWD 36

CIS-36, Russian Piccolo, URS Multitone, CIS 10 11 11 It is Soviet MFSK full duplex system on two transmission frequencies that can be also used in simplex mode. It uses 36 tones based on the British Piccolo. This system runs usually at 40 Bd with a single tone lasting 25ms and hand keyed traffic between operators at 10 Bd with a single tone lasting 100ms. A spectrum analyzer will show the tones arranged in 3 distinct groups of 10+11+11 tones spaced 40 Hz. Tones 1, 12, 24 and 36 are rarely used so you are likely to see an 80 Hz gap between groups. Each of the 32 tones represents one ITA2 character code. CIS diplomatic and Mil service is the main user with suspected use by CIS Intel and Military services. Idle tone is number 24. For encryption a shift register can be used. CROWD 36 is transmitting blocks of ten data frames and an additional parity frame. Each data frame contains five data characters with one parity character. In case an error is detected the receiving station requests a frame repetition (NAK instead of ACK) from the last complete and correctly received frame. There are several 4 letter groups or control sequences used for different transmission modes. For example: VDAE VDBA Change to chat modus VDBG VDGB VDCB VDCE resynchronisation? VDFB break VDEA end of transmission

Table 42: Crowd 36 control sequences

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Picture 187: Spectrum of CROWD 36

Preamble and 5 letter group transmission

Op chat : ‘RYRYRY’ and ‘CFM’

Op chat: ‘QSL’ and ‘end of

transmission’

Picture 188: Crowd 36 in sonagram display

78. CROWD 36 Selective Calling

This mode is used for calling a station in the network outside the scheduled times.

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Picture 189: Spectrum of CROWD 36 selective calling

Picture 190: Sonagram of CROWD 36 selective calling

79. CW

Morse The oldest “data” transmission, still in use by the Amateur community, Marine and Military operations. The standard code is as follows:

A .- N -. 1 .---- . .-.-.- B -… O --- 2 ..--- , --..-- C -.-. P .--. 3 …-- ? ..--.. D -.. Q -.-- 4 ….- ( -.--. E . R .-. 5 ….. ) -.--.- F ..-. S … 6 -…. - -….- G --. T - 7 --… “ .-..-. H …. U ..- 8 ---.. _ ..--.- I .. V …- 9 ----. ‘ .----.

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J .--- W .-- 0 ----- : ---... K -.- X -..- / -..-. ; -.-.-. L .-.. Y -.-- + .-.-. $ ...-..- M -- Z --.. = -…-

Table 43: Morse alphabet

80. CW-F1B

FSK Morse, Morse F1B

In this special mode of a standard FSK the morse character are keyed by using the two frequencies of the FSK.

81. D AF VFT

This VFT with 3 channels is in use by the German Airforce. It is transmitting three channels with 144 Bd or 192 Bd and 340 Hz Shift. The shift between channels is 680 Hz. This system can often be heard for communication training.

Picture 191: Spectrum of a D AF VFT signal

82. DGPS

Differential Global Positioning System DGPS transmissions are broadcasted in the 284.5 KHz to 325 KHz band which is allocated for maritime radio navigation (radio beacons). Marine radio beacons are used to broadcast DGPS

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signals on the main carrier using Minimum Shift Keying (MSK) modulation. DGPS stations have also been monitored in the frequency range up to 7 MHz. The baud rate can be 100 Bd or 200 Bd. There have been stations monitored with 300 Bd and a shift of 200 Hz.

Picture 192: Spectrum of a DGPS signal with 100 Bd

The modulated signal is containing DGPS information and the identification of the transmitting DGPS station according to the RTCM SC104 standard. Broadcasted message types are 3, 5, 6, 7, 9 and 16. DGPS data are transmitted in frames. The two first words of each frame are containing the reference station ID, the message type, a sequence number and the health of the station. The station health gives the resolution of the user differential range error (UDRE). Each data word has a length of 30 bits with 24 bits data and 6 bits parity.

Parameter Bits Description Preamble 8 Fixed pattern 0110 0110 Message type 6 0 – 63 Station number 10 0 – 1023 Modified z count 13 Counts from 0 to 6000 every 0.6 s Seq 3 Counts from 0 to 7 N 5 Number of data words following 0 - 31 Station health 3 111 = unhealthy broadcast

110 = unmonitored broadcast 101 = UDRE Scale Factor = 0.10 100 = UDRE Scale Factor = 0.20 011 = UDRE Scale Factor = 0.30 010 = UDRE Scale Factor = 0.50 001 = UDRE Scale Factor = 0.75 000 = UDRE Scale Factor = 1.00

Parity 2 x 6 XOR

Table 44: Data structure of DGPS

TX numbers The TX number in the first header word identifies the received beacon. Two numbers exits: 1. GPS reference station number and 2. DGPS broadcast station number. Some authorities use the RTCM standard and send the reference station number, others use the TX number.

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Message types

Type 3 Message

A Type 3 message contains information on the identity and surveyed position of the active reference station in the DGPS station. Two reference stations are provided in a DGPS station (dual redundancy). At any given time one will be on air and the other will serve as a .hot standby. In the event of a reference station changeover, the position coordinates which are broadcast in the Type 3 Message will change to reflect the other reference station surveyed position and its identity. The Type 3 Message will contain NAD 83 coordinates since this system is the only one in North America that can take advantage of the centimetre resolution provided in this message.

Type 5 Message The Type 5 message will notify the user equipment suite that a satellite that is deemed unhealthy by its current navigation message is usable for DGPS navigation. This is accomplished by the setting of the “Health Enable Function” in the Type 5 Message by the reference station in order to indicate this condition. An example of this situation is a slowly drifting satellite clock that may render a satellite unhealthy for GPS use, but would be correctable by the reference station for DGPS use. The user equipment suite should not use an unhealthy satellite unless a Type 5 Message allowing the use of an unhealthy satellite was received within the last thirty minutes. If the most recent Type 5 Message received does not indicate that an unhealthy satellite can be utilized, then the use of that satellite should be discontinued if it were being used earlier (i.e. via a previous Type 5 Message).

Type 7 Message A Type 7 Message provides information of its broadcasting DGPS station and the other two or three adjacent DGPS stations. Where adjacent stations are under US jurisdiction, appropriate arrangements will be made to provide reciprocal information. The user equipment suite should update its internal almanac immediately as new information is received. Non volatile memory should be employed to store the internal almanac. When a broadcast becomes unhealthy or unmonitored in a DGPS coverage area, the Type 7 Message will be set to indicate the subject condition. Upon receiving the next Type 7 message, the user’s equipment suite should immediately update its internal almanac. Additionally, the user equipment suite is immediately notified by means of the station health status indicator contained in the second word of the universal message header. The user should be able to view the contents of the current Type 7 Message in order to obtain information on coverage areas that may soon be entered.

Type 9 Message Due to the advantages of greater impulse noise immunity, lower latency and a timely alarm capability, the Type 9 Message has been selected for broadcasting pseudo range corrections instead of the Type 1 Message. Two methods of transmitting the Type 9 message are possible.

Type 9-3 Message The first method of broadcasting PRC’s (Pseudo Range Corrections) is based upon “Three-Satellite “Type 9 Messages. This is denoted as Type 9-3 Message. In this method all satellites for which corrections are broadcast are assigned to either three satellite

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Type 9 Messages or to a remainder message of either one or two satellites. The transmission rate could be at either 100 or 200 bps. For example, the pseudo range corrections for eight satellites will consist of three Type 9 Messages, two with 3 satellites and one with two satellites. An equal number of corrections are broadcast for each satellite. In order to optimize use of the UDRE Scale Factor in the message header, satellites will be grouped in messages by their UDRE values. At a transmission rate of 200 bps this represents a minimum of a forty percent reduction in message loss as compared to a Type 1 Message under high noise conditions broadcast at the same bit rate. The relative latency of the different PRC message types is illustrated in Figure 2 - note that since the corrections can be applied as soon as the parity is verified for the words that contain a given correction, the latencies in Figure 3 are the maximum latencies. PRC accuracy is for the most part a function of the latency of the Range Rate Correction (RRC) since it is the only PRC component in which the error is a function of time. The error of the PRC (t0) term is fixed at the time of measurement and any errors that result from its propagation are a function of RRC accuracy. Figure 3 illustrates an additional advantage of the Type 9 Message - the phasing of the PRCs. When the latency for certain satellites is nearing its maximum the latency for others is very low. This provides a built-in immunity factor to high pseudo range accelerations on one or more satellites. The potential to weight pseudo ranges on the basis of latency is readily apparent and should be beneficial to the user. This method of transmitting a Type 9 message at 100 bps and 200 bps will be used for the standard and enhanced/multiple coverage areas respectively.

Type 9-1 Message The second method of broadcasting pseudo range corrections is to broadcast individual Type 9 Messages for each satellite at a transmission rate of 50 Bps. This message is referred to as the “Single Satellite” Type 9 Message. and is denoted in this document as the Type 9-1 Message. A high level of impulse noise immunity is achieved by this technique that will extend the effective range of the broadcast. Lower transmission rates such as 50 bps could not be used at this time because of the need to meet the time to alarm requirement due to the length of the PRC Messages. An equal number of corrections are broadcast for all satellites regardless of their pseudo range rates or accelerations The following table summarizes the above mentioned methods of Type 9 message transmission.

Method Message Type Data Rate Trans. Rate 1a Type 9-3 200 Bps 200 Bps 1b Type 9-3 100 Bps 100 Bps 21 Type 9-1 50 Bps 50 Bps

Table 45: PRC Message Broadcast Parameters

Since each Type 9 Message contains the freshest possible corrections, the corrections contained in each and every Type 9 Message are computed at different times (i.e. computed at the latest possible time before broadcast). The user equipment suite can mix corrections that may have been computed up to 30 seconds apart, thus the reference station should utilize a highly stable frequency source, within one part in 10-11 (30 second Allan Variance). The use of a highly stable frequency reference and a tightly controlled clock provides the additional benefit of allowing corrections for each satellite to be applied as they are received, as long as the parity for both of the words which contain a given correction is verified. This capability should be implemented for the Type 9 Message in all user equipment suites. Generally, the Reference Station clock will be within 100 ns of GPS time. Clock stability is of far greater priority then absolute time accuracy since PRC's are generated relative to each other for a given Reference Station. The shorter message length and greater frequency of preambles provided by the Type 9 Message result in a substantially improved impulse noise performance as compared with the Type 1 Message. The higher rate of preambles allows a

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much faster re-synchronization, especially during high noise periods. As previously discussed, even in low noise conditions the Type 9-3 Message provides a lower latency than the Type 1 Message, making it advantageous when operating with a low data rate as well as in high noise environments. This is especially useful since the position error growth due to latency is non-linear. If a satellite suddenly becomes unhealthy when in use by a given reference station the PRC (to) and the RRC are set to predefined values as delineated in RTCM SC104 (Version 2.1) that designate this condition.

Type 16 Message The Type 16 message will be utilized as a timely supplement to the notice to mariners or shipping, regarding information on the status of the local DGPS service that is not provided in other message types. Additionally, the Type 16 Message may provide limited information on service outages in adjacent coverage areas or planned outages for scheduled maintenance at any broadcast site. In order to keep data link loading to a minimum, Type 16 Messages will contain only system information that is crucial to the safety of navigation. Any broadcast of the Type 16 Message will not exceed 4.8 seconds. At 200 bps this translates into 32 words that allow a maximum 90 characters after accounting for the message header. The Type 16 Message is not intended to act as a substitute for the notice to mariners, even though it pertains to DGPS information. Type 16 Messages will be utilized to alert the user of an outage condition for which a broadcast in an adjacent coverage area may be unhealthy, unmonitored, or unavailable. This information would be useful to the mariner who is planning a transit through an affected area or whose equipment suite is presently incapable of automatic selection from the beacon almanac. Further details of an outage condition can be derived from the Type 7 Message for route planning purposes. DGPS Message Scheduling The routine data stream will consist mainly of message types 3, 7, & 9 and broadcast of message types 5,6 and 16 will be on an exceptional basis. Due to the advent of continuous tracking receivers the Type 2 Message is no longer required and its use would only serve to increase the latency of the broadcast. For each new Issue of Data (IOD) there will be a 90 second delay before the broadcast pseudo range corrections are computed with the new IOD. Ninety seconds should be more than adequate for a continuously tracking DGPS receiver, as it will be able to instantaneously read the navigation messages as they are broadcast from each satellite. Any short term blockage of a satellite at IOD, such as passing under a bridge, are compensated for by the ninety second delay. This method of handling a new IOD requires the user equipment suite to store both the new and the old IOD for the subject period. Message Types 3, 5, 7, 15 and 16 will not be broadcast within 90 seconds of each other under any circumstances.

Type 3 Message Type 3 Messages will be broadcast at fifteen and forty-five minutes past the hour.

Type 5 Message If an unhealthy satellite is deemed usable for DGPS, a Type 5 Message will be broadcast at fifteen minute intervals beginning at five minutes past the hour. If an unhealthy satellite that was deemed usable is later deemed unusable the reference station will no longer broadcast corrections for the subject satellite.

Type 7 Message

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A routine Type 7 Message will be broadcast at ten minute intervals beginning at seven minutes past the hour. Special Type 7 Messages will be broadcast as soon as possible, subject to the other scheduling constraints, when the status of a beacon in the almanac changes. This will aid the user equipment suite in its choice of the proper beacon.

Type 9 Message Pseudo range corrections will be broadcast only for satellites at an elevation angle of 7.5 degrees or higher through use of the Type 9 Message. The official GPS coverage is based on elevation angles of ten degrees or higher. Satellites at elevation angles lower than 7.5 degrees are adversely affected by spatial decorrelation, multipath, and minimal processing time between acquisition and actual use. The level of 7.5 degrees is identical to that recommended by RTCA Special Committee 159. Corrections for all satellites in view above the mask angle will be broadcast. Positioning users of the system who are interested in achieving the highest accuracy level possible should use a higher mask angle in order to avoid the more pronounced atmospheric effects associated with satellites at low elevation angles. When a reference station drops a satellite it will broadcast an indication to the user equipment suite to stop applying corrections for that satellite to its navigation solution

Type 16 Message This message type will be broadcast as deemed necessary but within strict limits. The interval between successive Type 16 Messages will be no less than three minutes.

83. DominoF

DominoF is an experimental amateur mode with dual interleaved tone sets, each of 16 tones. DominoF uses a tone spacing of 10.766 Hz. The total bandwidth is 213 Hz. In fact, 18 tones (2 x 9) are used to limit the rotations. A character is composed of 2 symbols of 3 bits each, each symbol being sent on a tone set (first symbol on J1 then second symbol on J2). The character set has 62 characters (lower case, numbers and some punctuation) & an error reset character (6 bits long characters) & a synchronization character. DOMINO is the name given by the developers to a family of IFK coded coherent phase single tone MFSK keyed modes, using sequential tones in spectrum-managed orthogonal tone sets

The tone sets are arranged so that ionospheric modulation products cannot easily spill from one possible tone position to another or from one symbol to the next. In DominoF, this was done by double-spacing the tones and interleaving the tone sets. DominoF had two independent tone sets, used alternately, to ensure that tones could not overlap. Another advantage was that the alternation is very quickly detected as an odd-even component in the receiver FFT, and this was used to provide sync. Sync lock-up time was well under one second. Interleaving the tone sets does reduce the necessary bandwidth.

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84. DominoEX

DominoEX is an experimental amateur mode using a MFSK with 18 tones which are separated by a shift which is related to the transmission speed. The main data of this waveform are collected in the following table:

Mode Baud rate WPM Tone Shift Total Bandwidth

DominoEX 4 3.90625 Bd 27 7.8125 Hz 140 Hz DominoEX 7 5.3833 Bd 38 10.766 Hz 194 Hz DominoEX 8 7.8125 Bd 55 15.625 Hz 281 Hz DominoEX 11 10.766 Bd 77 10.766 Hz 194 Hz DominoEX 16 15.625 Bd 110 15.625 Hz 281 Hz DominoEX 22 21.533 Bd 154 21.533 Hz 388 Hz

Table 46: DominoEX waveforms

DominoEX is using the incremental frequency keying (IFK). Each transmitted character is composed of 1 to 3 "nibbles" (group of 4 bits). The first one is called "Initial nibble" and has a value between 0 and 7, the 2 others are called "Continuation nibbles" and have a value between 0 and 15. The "initial nibble" is compulsory and, from its value, permits to know that it is the first 4 bits start of the character. The "continuation nibbles" exist only depending of the transmitted character. Only one tone is used for a given "nibble". For determination of the tone number, it is used the following formula: * Tone number (between 0 and 17) = Previous tone number + data nibble (0 to 15) +2 * If the tone number>=18 then Tone number = Tone number -18

Picture 193: Spectrum of DominoEX with 4 Bd

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Picture 194: Spectrum of DominoEX with 11 Bd

Picture 195: Spectrum of DominoEX with 22 Bd

85. DPRK ARQ 600 Bd

This teletyper is used by the Democratic People Republic of Korea (DPRK) with 600 Bd and 600 Hz shift for diplomatic traffic in ARQ mode. The block length is 217 ms, the pause 323 ms so that the total packet has a length of 540 ms. Each bit has a length of 1.67 ms so that one packet has 130 bit

Picture 196: Spectrum of DPRK FSK in ARQ mode

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possible by transmitting radio waves at frequency of 9.2 MHz with maximum transmission power of 1 kW. In Japan, it is almost impossible to secure a sufficiently wide and continuous frequency bandwidth in the HF band, so the LROR adopts a frequency modulated interrupted continuous wave (FMICW) type radar that is able to use frequencies resources more efficiently than the short-pulse type radar. The sweep bandwidth is 22 kHz, which corresponds to the range resolution of about 7 km. The current velocity resolution, which is determined by the incoherent integration time of received signal, is 2.5 cm/s.

ig.3

Picture 412: Function of an Ocean Radar

245. LORAN-C

Long range Navigation LORAN is a navigation system used by ships and planes to accurately determine their position. It is hyperbolic navigation system which uses three to five transmitters. These transmitters are located several 100 miles on land. LORAN transmits on a centre frequency of 100 kHz. The net has one master station and several secondary stations which are called W, X, Y and Z. The transmission signal of the secondary stations are synchronised to the signal of the master station. For navigation is measured the time difference between the master station and a minimum of two secondary stations. This measurement gives to every station a line of position. The cross point of several lines of position gives the location of the user. Every LORAN - C net is transmitting group repetition intervals which is unique for this net. Every master has 10 ms and the secondary station 8 ms for his group transmission. The minimum length of group of intervals is determined by the number of stations. The master station is transmitting 8 pulses with a space of 1000us, additional a ninth pulse which follows after 2000 us behind the 8. pulse.

Picture 413: Transmission of LORAN-C

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The secondary station is transmitting 8 pulses with a space of 1000 us. The ninth pulse gives the information, that the pulse group is transmitted by a master station. The pulse is also coded for internal information. The identification of the group repetition interval is a fixed length divided by ten. The following table gives the LORAN-C nets working in different areas: GRI number Location of LORAN - C net 9990 North Pacific 9970 North West Pacific 9960 USA North East Coast 9940 USA West Coast 8970 Great Lakes 7990 Mediterranean Sea 7980 USA South East Coast 7970 Norway Sea 7960 Gulf of Alaska 7930 North Atlantic 5990 Canadian Pacific Coast 5930 Canadian Atlantic Coast 4990 Central Pacific 9980 Iceland 8000 Russia West 8990 Saudi Arabia North 7170 Saudi Arabia South 8290 USA North 9610 USA South 7950 Russia East 5970 Asia East 6930 China India Bombay India Calcutta

Table 106: LORAN chains and their identification numbers

LORAN data channel communication (LDC) During the operation of the LORAN system it was desired to add a communication functionality to the current LORAN-C signal. The capabilities should include:

the transmission of absolute time, Differential LORAN corrections for maritime and timing users, anomalous propagation (early sky wave) warnings and LDC system information for high-integrity applications.

Ninth-Pulse Modulation

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This modulation scheme was chosen for its negligible impact on the current operational LORAN-C signal, and its facility for cancellation of cross-rate interference. Here, an additional pulse is inserted in time following the eighth pulse of the LORAN pulse group. Thirty-two state Pulse-position modulation is used to change the time delay of this pulse from the zero-symbol offset. In this manner, the data transfer rate is five bits per group repetition interval (GRI). The phase code of the 9

th

pulse is the same as the phase code of the last navigation pulse. The zero-symbol offset is 1000 microseconds after the 8

th

navigation pulse. The remaining 31 symbols are positioned in time a specific number of microseconds later in relationship to the zero symbol.

Messages All messages are 120 bits in length and consist of 3 components: a 4-bit type, a 41-bit payload, and a 75-bit parity component as shown in Table 2. The messages are transmitted 5bits/GRI. The time length of the messages is 24 GRI (maximum of approximately 2.4 seconds).

Section Type Payload Parity

Length (bits) 4 41 75

Bit assignment 0…3 4…44 45…119

Table 107: LORAN Data Channel message components

246. MF RADAR

MF radars are used for measurments on freuencies between 2 and 3 MHz and allow the cointinuous observation of the mesosphere in heights of 50 km to 95 km during the entire year. The radar are used for studies of the dynamic of the mesosphere, turbulences, internal gravity waves, tides and planetary waves. In Juliusruh a MF radar on the frequency 3,18 MHz is operated. It is a puls radar, which is equipped with a modular transmit and receive system with distributed power and a so-called Mills-Cross antenna. This antenna radiates a beam of a width of 18° which can be directed from the vertical elevation to any direction in the sky. It works in defined time angles and also allows DBS (Doppler-Beam-Swinging-Mode) measurements. The puls power is 128 kW with a puls width of 27 us. The hight resolution is 4 km and the sample resolution 1 km. The spektrum of this radar is shwon in the next picture:

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Picture 414: Spectrum of the MF radar at Juliusruh

The time distance between pulses is 12,5 ms and shown in the following picture.

Picture 415: Puls repetition time of the MF radar at Juliusruh

247. NAVTEX

The stations in the NAVTEX system are transmitting navigational and meteorological warnings and other important information. It is a part of the Maritime Safety Information (MSI) net which is part of the Global Maritime Distress and Safety System (GMDSS). The information is transmitted on 518 kHz by selected coast stations in SITOR B. The baud rate is 100 Bd with a shift of 170 Hz.

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This time shared service is designed for a distance of 400 nautical miles around the coast station.

Picture 416: Spectrum of a NAVTEX signal

For differentiation the following identifications are used: A : navigational warnings B : meteorological warnings C : ice messages D : search and rescue information E : meteorological forecast F : pilot message G : information about DECCA H : information about LORAN - C I : information about OMEGA J : information about SATNAV K : information about other navigational systems L : navigational warnings Z : QRU

Table 108: NAVTEX identification letters

NAVTEX messages are started with an identification group which has the following meaning: 1. ZCZC followed by the identification letter of radio station with message number 2. Identification for message type 3. Date/Time group 4. Message 5. Ending with NNNN

Table 109: Structure of a NAVTEX message

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248. NBTV

Narrow Band Television The following information about all NBTV modes are taken from the webpage www.qsl.net/Zl1bpu/NBTV with permission by Murray Greenman NBTV (Narrow Band Television) is a technique with some similarity to SSTV, and some to conventional FSTV (Fast Scan TV). Like SSTV, it operates in a narrow bandwidth, suited to an HF SSB transceiver, but rather than send individual image frames, NBTV is designed to send multiple frames one after the other, in much the same way as FSTV, but with considerably slower frame rate. This idea allows frame-averaging to be used on noisy channels, and enables the transmission of moving images.

For the technique to be practical, the frame rate must of course be much slower, the image resolution is much reduced, and various compression techniques must be used, along with a range of strategies designed to reduce or eliminate the effects of propagation, especially noise and multi-path fading and timing errors.

The image resolution is generally lower than it is for SSTV, but this is made up for by the motion effects, and also by the faster frame rate, typically 1 - 10 seconds per frame, rather than 30 seconds or more for SSTV.

Three systems are described here. They are broadly, analogue, digital, and hybrid designs, and all were developed by Con Wassilieff ZL2AFP, the acknowledged world expert on NBTV, and to date the only developer of modes that are successful on HF (there have been modes which work on VHF or on telephone lines). These new systems use sophisticated techniques, including digital signal processing, forward error correction, image compression and even path equalization. The three modes are:

Orthogonal Frequency Division Multiplex Analogue OFDM NBTV Single-tone 2000 baud PSK modem Digital NBTV Hybrid FM NBTV with PN-sequence synchronization

With all three of these systems you can transmit live pictures from a web camera, TV capture card or TV camera, send still frames in any image format and any size, and transmit movie clips in several formats. Because the frame rate is low, the receiving programs allow transmissions to be recorded, and played back later at movie speed.

Compared with SSTV, which sends even more slowly (and still has trouble with multi-path propagation tearing the images) NBTV must send faster, and is therefore even more prone to ionospheric effects. Thus the unconventional nature of these designs is explained by the emphasis on managing or countering these effects.

These different NBTV programs enable low and modest resolution B&W and colour TV images to be transmitted at modest power, and received via a limited performance HF radio channel. The systems has been optimized for specific radio conditions; most are designed for NVIS conditions (such as the

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Amateur 80m band at night); but there are other versions with better resolution, more suited to higher bands; and at least one faster version for VHF. In most cases the pictures are easily tuned with practice, as the software provides special tuning aids.

All three systems operate using a conventional digital modes setup: PC, sound card, radio interface with audio and PTT functions, and an SSB or (on VHF) FM transceiver. Use the links below to explore these modes further.

249. OFDM NBTV

OFDM NBTV is an analogue technique, in fact it is a true Fuzzy design as well. The transmission technique used is quite different from conventional TV - each line is transmitted separately, but all lines are sent at the same time, on a slightly different frequency. Because the transmitter and receiver operate at precisely the same speed, controlled by the computer sound card, there is no need for any sync pulses to align the picture; in fact there is no automatic synchronizing mechanism at all - it simply isn't necessary. The following picture is showing the typical spectrum of the OFDM signal:

Picture 417: Spectrum of an OFDM

Modulation on each of the many carriers is very narrow FM (a few Hz), for best noise rejection, and the overall transmission bandwidth is only 2 kHz, so an SSB transmitter and receiver can be used. These modes are Fuzzy Modes, which means that although the computer samples the images for transmission and display, the signals are essentially analogue in nature, and at the receiver the images are presented without decoding decision or interpretation by the computer - they are interpreted by eye and brain at the receiver. This means that the signals are inherently very noise immune and continue to be useable despite interference and propagation effects until they fade into the noise. The design is very versatile, and you can use still photographs (like a slide show), moving GIF images, AVI movies and many different types of live video, including 'web cams', video capture cards, digital cameras, screen shots from other software, and even live (fast scan) TV, although only one frame in many is transmitted in this case. A 'drag-and-drop' technique makes all this very easy.

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Limitations Because of the low bandwidth, it is not possible to send moving pictures in real time. Each image frame takes from one second to nine seconds to transmit, depending on the mode used. However, the received signal can be recorded and later played back faster for a very realistic effect. Standard .AVI format files are used, and the transmitters can also retransmit previous recordings. The images can also be post-processed for noise reduction and smooth motion effect. The quality of moving images is such that you'd never believe that the pictures contain only 48 or 72 lines!

On lower HF bands, especially with NVIS conditions (strong fading and multi-path reception), performance suffers as noise and colour stripes invade the picture. The 96 x 72 pixel colour mode is most affected. However, on the higher bands and VHF, the pictures are superb.

Another limitation is that tuning requirements are fairly stiff - a VFO rig CANNOT be used - it simply isn't stable enough. Most modern synthesized transceivers are OK if used with care. Tuning needs to be within 1Hz of the transmission. On VHF the secret is to use FM transceivers, and thus avoid the problem completely.

The OFDM NBTV Modes There are in total five modes, two black and white, and three colour. There is some compatibility between the B&W and Colour modes, so you can soon work out which is being transmitted. There are two different image resolutions, 48 x 48 pixel low resolution (which is faster and more robust), and 96 x 72 pixel modest resolution, which of course is slower, but gives more picture detail. A special compressed 96 x 72 pixel colour-only version is provided - this provides a frame rate twice as fast as the standard 96 x 72 colour mode, but is suited only to higher bands and VHF. The picture on the right below shows typical 48 x 48 colour reception.

48 x 48 Low resolution B&W and RGB colour for NVIS conditions 96 x 72 Modest resolution B&W and RGB colour for HF use 96 x 72 Modest resolution compressed RGGB colour for VHF

The following table shows an overview of the technical parameter of these modes:

Mode Image Properties Pixel Rate Frame Period Bandwidth BW 48 48 x 48 Black & White 50 Hz 1.0 s 2100 Hz CO 48 48 x 48 RGB 50 Hz 3.0 s 2100 Hz BW 96 96 x 72 Black & White 33 Hz 3.0 s 2100 Hz CO 96 96 x 72 RGB 33 Hz 9.0 s 2100 Hz RGGB 96 x 72 RGGB 33 Hz 6.0 s 2100 Hz

Table 110: OFDM NBTV modes

48 x 48 Mode

In this mode, there are 48 carriers, spaced 42Hz apart, one carrier for each picture line. The total signal is therefore about 2 kHz wide. This includes a 'pilot carrier', transmitted in the middle of the image carriers (see picture above). This is slowly sine-wave modulated, and used for fine tuning.

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In the B&W option, just one field is transmitted per frame. With 48 pixels per line, each pixel takes 20ms to transmit, and the carrier modulation bandwidth is about 40Hz. At the end of each line a vertical dotted line is transmitted, so the end of frame can be identified. In colour mode, three separate fields, much the same as described, are transmitted for Red, Green and Blue image data. At the end of the third (blue) field of, a vertical dotted line is transmitted, so again the end of frame can be identified. In this case it also identifies the correct colour order (you can see this line at the left of the picture). The picture has a square (1:1) aspect ratio.

Picture 418: Spectrum of 48 x 48 OFDM NBTV

96 x 72 Mode This mode uses 72 carriers, spaced 32Hz apart, again one carrier for each picture line. There is one 'pilot carrier', right in the middle of the picture carriers. The pixel modulation rate is lower, and so the carriers can be closer together. The total signal bandwidth is also about 2kHz. In the B&W mode, just one field is transmitted per frame. There are 96 pixels per line, and each pixel takes 30ms to transmit. As in the 48 x 48 modes, the end of each frame is identified by a vertical dotted line. In colour mode, three separate fields are transmitted for Red, Green and Blue image data. At the end of the third (blue) frame, a vertical dotted line is transmitted, so again the end of frame and correct colour order can be identified. The picture has a standard TV (4:3) aspect ratio.

96 x 72 Mode

This mode uses 72 carriers, spaced 32Hz apart, again one carrier for each picture line. There is one 'pilot carrier', right in the middle of the picture carriers. The pixel modulation rate is lower, and so the carriers can be closer together. The total signal bandwidth is also about 2kHz. In the B&W mode, just one field is transmitted per frame. There are 96 pixels per line, and each pixel takes 30ms to transmit. As in the 48 x 48 modes, the end of each frame is identified by a vertical dotted line. In colour mode, three separate fields are transmitted for Red, Green and Blue image data. At the end of the third (blue) frame, a vertical dotted line is transmitted, so again the end of frame and correct colour order can be identified. The picture has a standard TV (4:3) aspect ratio.

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Picture 419: Spectrum of 96 x 72 OFDM NBTV

250. Digital NBTV

A number of problems experienced with the OFDM NBTV system led to the development of this Digital NBTV mode. First, the OFDM signal is very difficult to tune, especially for beginners, and requires extreme transceiver accuracy and stability. Then in addition, the pictures tend to be noisy and individual frames can be marred by multi-path effects, especially when used on the lower bands. The approach taken for the Digital NBTV mode is completely different, in many senses: It uses separate programs for modem and codec in the transmitter and receiver TCP/IP communications is used between program modules The modem is high speed single-tone PSK, similar to NATO's STANAG 4285. An equalizer system is included to compensate for ionospheric path variation Wavelet image compression and forward error correction are used. It provides completely noise-free and error-free image reception, even on 80m. So nothing could be more different! The transmission consists of a stream of packets, each containing data for a small number of image lines. The amount of data in the packet varies according to the image complexity, the compression level and the level of forward error correction included, but the packet size is constant at 256 symbols plus an 80 symbol header. Modulation Digital NBTV uses a modulation technique which is widely used by high speed HF radio modems. A single 1500Hz phase modulated carrier is used to send both packet sync and payload. Using BPSK modulation, a pseudo-random binary (PN) sequence starts each packet, and is used to identify an exact point in the transmission from which the data can be synchronized. The audio spectrum is shown in the following picture:

Picture 420: Spectrum of digital NBTV

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A cross-correlator is used in the receiver to locate the one point in the whole message where the sequence matches up with the local copy of the sequence. The cross-correlator works with a known pattern to look for, and is a very powerful and sensitive tool. These radio modems use the PN sequence technique to enable complex high speed data to be decoded accurately - the ranging information determined from the cross-correlator is used to correct the received data timing to reduce errors induced by the ionosphere, using a signal processing device called an 'equalizer'. The equalizer also corrects for Doppler errors which affect carrier phase, making the use of 8-PSK practical. The phase constellation is shown in the next picture:

Picture 421: Phase plane of digital NBTV

The two dots on 135° and 315° are bigger in size and density. This is caused by the BPSK which is used for synchronisation. Digital NBTV uses a 31-bit PN sequence borrowed from STANAG 4285, with one chance in two billion of a perfect score being caused by noise. It uses 80 symbols (modulation time slots) to send this sequence about 2.5 times. Each packet is contained in a 336 symbol frame. 256 symbols are used for image data and FEC information. Since 4-PSK is used for the data, each packet could contain 512 bits of image data, or 3047 bps raw data rate. The data symbols are scrambled in an 8-PSK pattern to improve resistance to selective fades.

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Picture 422: Framing of digital NBTV

Like the STANAG 4285 system, single-tone PSK Digital NBTV can also operate at 2400 baud, using a sub-carrier frequency of 1800Hz. The corresponding bandwidth (just under 3kHz) is too much for most HF transceivers, but quite suitable for VHF, and gives a worthwhile speed improvement. However, to fit the signal into a normal amateur transceiver IF, it is usually operated at 2000 baud using a 1500Hz sub-carrier. The following picture shows the measurement of the baudrate of 2000 Bd with the help of a phase spectrum:

Picture 423: Baudrate measurement of digital NBTV

Modem

The modem section of the transmitter or receiver converts digital data into PSK audio for the transmitter, or received audio into digital data, respectively. The receiver modem also has to manage sync and equalization. Each transmitted packet commences with a BPSK pseudo-random (PN) sequence (same sequence as STANAG 4285), which is used to synchronize the receiver timing with the start of the packet, and also serves as a measuring point for the receiver equalizer software which measures and compensates for frequency offset and drift, and other code which compensates for timing errors. Detection of the PN sequence is achieved using a cross-correlator. This technique is extremely sensitive, so no matter how weak the signal is, packet synchronization is secure. The packet data payload is transmitted as 4-PSK, to ensure a high data rate. There are nearly six packets per second, using a 2000 baud modem.