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Copyright NVIS Communications, All rights reserved

NVIS Communications Training Academy

Basic HF Voice Operator 1 Introduction to HF-NVIS Radio

Communications

– Introductory Radio Principles– Why HF radio has become important– Basic HF Radio Technologies


Introductory Radio Principles


– Electromagnetic (EM) Waves– EM Waves in the Radio Spectrum– High Frequency (HF) in the radio spectrum– Near Vertical Incident Skywave (NVIS)



It all starts with….

However, please feel free to use these

wavelengths to watch this presentation.

They are a fundamental, observable phenomenon in our universe– Made of electric waves combined with magnetic waves.

– They travel through the universe at the speed of light. (they are light)

– They range in wavelength from radio waves, to visible light, and beyond.

Image courtesy of NASAThe Electromagnetic Spectrum from radio waves, through visible light, and beyond

We are interested in waves at radio wavelengths

MF HF VHF UHF

Electromagnetic Waves


The radio portion of the EM spectrum

“Shortwave”.3 MHz 1000 m

3 MHz100 m

30 MHz10 m

300 MHz1 m

3 GHz.1 m

30 GHz.01 m

MFMedium Frequency

HFHigh Frequency

VHFVery High Frequency

UHFUltra High Frequency

SHFSuper High Frequency

VHF/UHF waves travel “line of sight”

MF waves hug the ground

HF waves refract from the ionosphere

Special techniques are required beyond here


Although not technically correct, the “HF” radio band is often said to be from 1.6 to 30 MHz. instead of from 3 to 30 MHz. This is because most “HF” radios operate between 1.6 and 30 MHz.


About HF (High Frequency) Radio Waves

HF radio waves refract and reflect from the ionosphere– If directed toward the horizon they may go long distances

– Maybe one hop, maybe many

– Maybe short hops, maybe long

– Generally includes dead “skip” zones



Instead of:

An early NVIS mobile

• An HF signal directed straight up will rain back down from the sky over hundreds of miles

About NVIS (Near Vertical Incident Skywave)



HF Long Distance vs. HF-NVIS

• Signal toward the horizon• High power, often 1KW+• Antennas must be elevated• May or may not work• Has dead “skip” zones• Spills beyond intended area• Makes spectrum re-use difficult

• Signal straight up• Low power, 125W is plenty• Antennas stay near the ground• Virtually always works• Blankets entire region• Stays in the regional area• Re-assign spectrum elsewhere

Ionosphere

Skip zone

Signal zone

Signal spilledbeyond target area

Regional signal blanket

Ionosphere

Spectrumre-usable elsewhere

HF Long Distance compared to HF-NVIS



HF Past and Present

Why its use faded and has now come back

HF Past and Present


Amateur Radio,Shortwave Broadcast,

Military

The history of our use of the radio spectrum

MFMedium Frequency

HFHigh Frequency

VHFVery High Frequency

UHFUltra High Frequency

SHFSuper High Frequency

AM Radio

Land Mobile Radio – Public Safety, business, government

Microwave, satellite, cellular,

wireless devices, etc.

HF is important again for fallback

communications

-- Band usage past and present --

1920s 1940s1930s 1950s 1960s… … …1910s

HF Past and Present


HF radiation patterns are complicated(But now we have computers)

• HF signal paths are very complex– Time of day, frequency, sunspots, …– Historically the operator had to figure this out– That was not ideal for public safety personnel

• Local government and industry moved to newer technologies– Local communications went to VHF and UHF– Long range went to T-carrier networks and the Internet

• But the HF-NVIS story is like the “Flying Wing”– Abandoned in 1950s because it was too complicated– Came back with computer control as the B2 bomber

HF frequency range

HF-NVIS is back under computer

control the same way!

HF Past and Present


Migration from the Past to Today

• Large, heavy equipment• Marketed for the military• Few vendors, very expensive• Complicated operation• Specially trained operators• Limited features• Not recognized for fallback use• Not on the public safety radar• Not known to critical infrastructures

• Smaller lightweight equipment• Marketed for govt., public safety• Competing vendors, cost effective• Simpler, menu operation• Your regular operational staff• Many voice/data features• The new Base Layer Fallback mode• Public safety lining up to get it• Critical infrastructures want it

Today

Products from several vendors

HF Past and Present

The Past


Why HF radio is critical for your future


• It has always been important for military, shortwave broadcast, and amateur radio.

• Now it is important again for government, public safety, and critical infrastructures


Fallback as opposed to Failover

• Failover preserves the primary operational mode using alternate resources.

• Fallback replaces the primary mode with simpler modes when the primary mode is not available at all..

• Base Layer Fallback is your lowest layer of prepared fallback for when everything else has failed. It must not have components in common with the primary mode.

Fallback Modes

Primary Operational Mode Failover

Modes



Fallback for regional and wide-area communications

• These systems have many complex layers of infrastructure, and this makes them inherently subject to failure regardless of the their capabilities for failover.

• HF-NVIS systems have no intervening infrastructure between stations, and this makes them immensely more resilient.

• Modern, automated HF-NVIS networks are taking their rightful place as the Base Layer Fallback Mode for federal, state, and local government and for critical infrastructures.

Primary systems: - Microwave, repeaters - Internet, PSTN - Hopefully FirstNet - …

Failover Measures

Many layers of alternate resources to keep the systems operational – Very important! However…

Critically needed Base Layer Fallback

HF-NVIS



Why HF-NVIIS has become our nation’sBase Layer Fallback Mode

• We now realize how vulnerable our systems are– Lessons from 9-11, Katrina, Sandy, and others

• We now understand our need for Base Layer Fallback

• Modern HF systems are available and easy to use– “Simple menu operation for calling– Automatic frequency selection and call connection– Cost effective for public safety use

• Leading edge agencies are adopting it!– Federal, state, and local governments– Critical Infrastructure providers– HF-NVIS is becoming our National FallbackNet



Plan for these being compromised

You can build your own Base Layer Fallback Network

Microwave

Satellite Internet

VHF/UHFLandlinesCellular

Normal Operations

Operational sites throughout your regional area



Have your own HF-NVIS network for selected staff personnel


You can build your own Base Layer Fallback Network



Interface directly to disaster communications organizations


(Licensing restrictions apply)

You can build your own Base Layer Fallback NetworkHave your own HF-NVIS network for selected staff personnel



Think of HF-NVIS as a safety net under our infrastructure-heavy primary systems

From an article by BBC News

• This net looks pretty makeshift

• It’s because they built it after the bear got stuck in the bridge.

• We should build ours before we get stuck!



Basic HF Radio Technology


– Single Sideband (SSB) Modulation– HF antennas and the “dipole” antenna– Automatic Link Establishment (ALE)


HF Radio Modulation: Single Side Band (SSB)

• Modulation physics is beyond the scope of this class

• However, there are several things you should know

– Modulation means putting information (voice, etc.) onto a radio wave

– VHF/UHF voice systems typically use Frequency Modulation (FM)

– FM works great for local, “line-of-sight” communications

– But SSB is the most effective modulation for long distances

– Unfortunately, SSB does not block out noise the way FM does.

– SSB signal rides on top of the noise, so it is not as clear as FM

– But for long distances, SSB will get through loud and clear where other

modes will simply fail



SSB vs FM from the user’s perspective

A traditional 25 KHz-wide FM signal

FM captures its wide bandwidth with a carrier wave of energy• For this reason FM blocks out noise within its bandwidth• This is why a strong FM signal has no background noise

25 KHz wide

12.5 KHz wide

A “narrowband” (NFM) signal is half as wide, but it is still FM

Many FM users have been required by the FCC to switch to “narrow band”

3 KHz wide

Single Side Band is a sliver of energy vibrating within a 3KHz bandwidth

• No carrier wave to block out noise, so noise is always there. However…• This narrow signal is easier to push long distances than a giant FM signal



HF Radio Antennas

• Antenna physics is beyond the scope of this class

• However, there are several things you should know

– Any wire or piece of metal can act as an antenna

– But a good antenna is sized for the radio wavelength it will be used for

– VHF/UHF antennas can be short because VHF/UHF wavelengths are short

– HF antennas must be long because HF wavelengths are long

– The wavelength of a 5 MHz HF radio wave is approx. 60 meters.

• A “dipole” antennas is ideally 1/2 of the wavelength it is used for– So the ideal length for 5 MHz would be 30 meters or 98 feet.

– HF antennas are often shorter than ideal for practical reasons.



The Classic Dipole Antenna

Two radiating elements extending in opposite directions.

Radiating element

Radiating element

Transmission line• 1. The radio emits an alternating current at a some frequency.

• 2. This creates alternating currents in the antenna elements

• 3. This causes electromagnetic (radio) waves to radiate into space.Radio

Dipole Antenna



Most installations use coaxial cable for transmission line

“Balun”Radiating element

Radiating element

Coaxial cable

• To feed a dipole, coaxial feed line needs an interface box called a “balun” – This balances the coax

signal equally between the two radiating elements.

– The physics of this are beyond the scope of this course

• Easy to route to an antenna

• Keeps the radio signal inside until it reaches the antenna

• Considered “unbalanced” because the two conductors inside it are not the same. – It has an inner conductor and

an outer shield.

Dipoles as used in most applications



Common HF-NVIS Base Antennas


` `

Single wire dipole

` `

Multi-wire dipole Portable dipole

Multi-wire dipole Multi-wire dipole


Common HF-NVIS Mobile Antennas

Base tuned whip folded over

Luggage rack half loop Roof mounted half loop



Automatic Link Establishment (ALE)

• A peer-to-peer HF network – Completely inside your radios

Site 1 Site 2

Site 3 Site 4

F1

F2

F4

F3

F5

F6

Your set of authorized HF frequencies that the radios scan



• Scheduled soundings– Every radio, will sound on

every frequency

– Dynamic models of the optimum frequencies

Site 1 testingOn F1,On F2,On F3, . . .

recording signal

strength

recording signal

strength

recording signal

strength

Site 1 Site 2

Site 3 Site 4

F1

F2

F4

F3

F5

F6

A set of authorized HF frequencies that the radios scan




• Place calls by unique radio ALE ID– User picks a contact from the list

– The radios pick the best frequency

– The receiving radio(s) ring like a telephone.

Site 1 calls Site 2 on the best frequency

Site 2 rings like a telephone

Site 1 Site 2

Site 3 Site 4

F1

F2

F4

F3

F5

F6



A set of authorized HF frequencies that the radios scan


Site 2 HFSite 1 HF

Gateways

Phone patch

Internet Email

FAX

VHF/UHF

Gateways

Phone patch

Internet Email

FAX

VHF/UHF

Data modes, gateways, ease of useVoice, email,

phone, SMS, fax

Easy to use

- Menu operations

- Auto freq. select

- Auto connect

- Contact lists

- Press to call

- Rings like phone

Third party extensions for ICS form data

ICS ICS



Basic use of your HF-NVIS system


– An hypothetical HF-NVIS network– Listening to SSB radio– Talking on SSB radio– Signal reporting on SSB radio– Squelch systems on SSB radio


Sacramento

San Jose

Los Angeles

Reno

Las Vegas

An example HF-NVIS network

Direct voice/data among all

stations for hundreds of

miles

Mobile



Sacramento

San Jose

Los Angeles

Reno

Las Vegas

“Sacramento now commencing this week’s all station

roll call.

An Example system

test

Sacramento places an ALE Group Call

All stations stop scanning and ring

“After roll call, all stations please

send an HF email to Sacramento.

Next week the test might be conducted by a different station



Sacramento

San Jose

Los Angeles

Reno

Las Vegas

During an emergency

Any station can call any

or all stations

Mobile

Since the network is tested often, people will know how to use it, and it will work when needed!



Listening to SSB Radio

• You may be used to listening to FM radio– Government and public safety radio is typically FM

– With FM the voice volume tends to stay the same whether it is a strong or weak signal

– If it is a strong signal, then there is no noise along with the voice. (“full quieting”)

– If it a weak signal, then the noise raises in volume until it drowns out the voice

• SSB sound characteristics – opposite from FM– With SSB it is the noise volume (rather than the voice volume) that tends to stay

the same

– If it is a strong signal, then the voice raises in volume and becomes louder than the noise.

– If it s weak signal, then the voice is lower in volume until it can no longer be heard through the noise



Talking on SSB Radio

• Use plain language

– No 10-codes or other service-specific jargon

– Remember, you may be talking with different services who do not know your jargon

– If talking with other services, identify yourself with a full, descriptive identifier

• Example: “ Los Angeles County Sheriff Mobile Command Unit 1”

• Learn to say “over” before you release the mike

– We do not do this on FM because users can hear when your carrier drops

– But remember, there is no carrier for them to hear on SSB!

– So tell them when you are releasing the mike by saying “over”.

• Signing off

– Say your identifier then say “out” or “clear”

– On HF people usually use “out”, but either one describes your intention

– Saying “over and out” may earn you some chuckles.



• You may be used to giving signal report s on FM radio:– For example “loud and clear”, “weak and scratchy”, “breaking up”, or

“unable to copy”.

• But remember that SSB characteristics are different– There is always noise, so saying “scratchy” is not informative

– Signal would not normally “break up”, but it may fade slowly in and out

– Since the characteristics are different, signal reporting is different.

• A commonly used range for SSB signal reporting :– “Loud and clear” (for a very loud signal)– “Good readable”– “Fair readable”– “Weak readable”– “Unable to copy”

Signal reports on SSB radio



Squelch systems for SSB– they

• Squelch quiets the speaker when nothing is being received– FM squelch detects the FM carrier of a received signal

– SSB has no carrier for a squelch system to detect

– SSB squelch therefore has to detect other things

• Types of SSB squelch– Audio squelch – tries to detect the characteristics of human voice

– Signal squelch – detects increased signal level (could be just noise)

– Selective Call – activates only when the digital ID for that station is received

• Using SSB squelch– SSB audio squelch and signal squelch are not as effective as FM squelch

– Most people leave their radios on Selective Call to receive only calls to them

– After Selective Call activates, it typically leaves the speaker ON (no squelch)

– Most people leave the speaker on during calls to hear everything

– This is in contrast to FM, which squelches the speaker after each received signal



NVIS Communications Training Academy

Congratulations on completing the classroom portion of:

Basic HF Voice Operator 1

Introduction to HF-NVIS Radio Communications

.

Practical Exercises for this material will now follow.

Subsequent courses will present more advanced topics.

copyright nvis communications, all rights reserved nvis communications training academy basic hf...

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