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The Link

Newsletter of the Durham FM Association

March 2020

Next Meeting is Tuesday, March 3rd, 6pm, at Bullock’s BBQ.

President’s Corner Asking for Help At the February club meeting, I asked you all for help deciding what the future of the Mobile Communication Unit would be. Not only did we have a

good discussion about its history and purpose, but some of you volunteered to put in the work needed to take care of it. I am truly grateful that you answered the call for help. After the February board meeting, we have a plan for permanent housing for the MCU. The future of the MCU looks bright. Stay tuned! Once we get out of this roller-coaster weather and firmly into spring, we’ll start having MCU work sessions. Having been successful in asking for help with the MCU, I’d like to ask for help with something else. One of the great things about our monthly meetings is our engaging and informative presenters. I’m looking for someone who can help recruit speakers for meetings. If you’d like to help, please let me know. 73, Jack — KM4MBG * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

In Memoriam: Joseph P. Fields, KF4QYY, sk Joseph, KF4QYY, passed away on 11/29/2019 at the age of 62. He grew up in Durham, earned a law degree and worked as a tax consultant. Joseph first became a ham in 1997 and held a General class license. He was a DFMA member from 1997 to 2008 and served as DurHamFest chair for several years. He frequented the DFMA repeaters and was a regular on the DFMA Thursday Night Net. He will be fondly remembered for his upbeat presence on the air. [Picture courtesy of Holloway Memorial Funeral Home]

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3DurHamFest Needs YOU!

DFMA and OCRA members please volunteer a few hours or more at one of areas listed on

the DFMA website, dfma.org or contact Dee, KU4GC, deeramm@gmail.com * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * FEBRUARY 10, 2020 LOOK4SAT: AN ANDROID APP FOR TRACKING AND PREDICTING AMATEUR RADIO AND WEATHER SATELLITE PASSES Thank you to Arty Bishop for submitting news about his recently released Android App called Look4Sat. Look4Sat is a satellite tracker and pass predictor with a focus on amateur radio and weather satellites. The app is free, ad free, and open source on GitHub. Arty writes that he's programmed this as a learning exercise and notes: I always wanted to have an offline and not bloated satellite tracker on my phone, as carrying the laptop at all times is kinda not too handy. The app uses predict4java library under the hood and is written in Kotlin. The TLE files are from Celestrak and the transmitters info is from SatNOGS and once they are ownloaded the app doesn't need an internet connection. The app creation and design is hugely inspired by Gpredict which is an absolutely brilliant piece of software. Thank you, Alexandru! Obviously there are no ads and it's totally free. Hope more people find Look4Sat useful. The features include:

• Calculating satellite passes for up to one week (168 hours) • Calculating passes for the current or manually entered location • Showing the list of currently active and upcoming satellite passes • Showing the active pass progress, polar trajectory and transceivers info • Showing the satellite positional data, footprint and ground track on a map • Offline first: pass prediction is done offline. It's up to you to decide when to update

the TLE file and the transceivers DB. (Weekly updates are recommended)

Look4Sat Android App Screenshots on Next Page

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5Running Linux SDR Programs on Windows 10

Thank you to Happysat who has shared with us a useful tutorial that explains how we can run Linux only SDR programs on a Windows 10 system using the Windows Subsystem For Linux (WSL) feature. WSL is a feature available on Windows 10, which is a Linux compatibility layer designed for running Linux binaries natively on Windows 10. This means that no Virtual Machine with shared resources is required. Instead, the full resources of your system are available. Happysat writes: Many people using Windows 10 now since Windows 7 is EOL and WSL is part of the system. It’s kinda "free", so why not use it :) Together with an X-Server and Desktop like XFCE4, it can be great for running SDR applications in Linux thru RTL-SDR. Very fast startup in seconds and not much packet loss thru tcp. Quite a few linux sdr applications are working very well. No allocating resources like a VM. Sometimes better then Ubuntu on a VM. Software tested: AX-25 Packet Radio, Dab Radio, DSD, Es-Hail Beacon Tracker, Sat Tracking with Gpredict and Gqrx, NOAA Reception WxToImg, Radiosonde Decoding, Shortwave Reception and some more tips and tricks about WSl and SDR. The steps appear to be fairly simple. Just enable WSL in the Windows 10 Features panel, download a Linux distro built for WSL and run the .exe file. Then you'll have access to a Linux terminal where you can install a GUI desktop environment, the RTL-SDR drivers, and other Linux SDR programs. Happysat’s tutorial shows how to install and use various Linux programs via WSL. It seems that the RTL-SDR cannot be directly accessed via the USB in WSL, however, the workaround is to simply run rtl_tcp in your Windows environment and connect to the local IP in the Linux environment. This means that only programs that accept rtl_tcp as an input, or demodulated audio from a program like GQRX can be used. The link to Happysat’s program: http://happysat.nl/Windows_WSL/index.html

Photo on next page showing GQRX Running on Windows 10 via WSL

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GQRX Running on Windows 10 via WSL

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * New World Distance Record Claimed on 122 GHz

7A new world distance record of 139 kilometers (86.2 miles) is being claimed by radio amateurs in northern California. This tops the record of 114 kilometers set in 2005 by WA1ZMS and W4WWQ, according to the Distance Records on the ARRL website. The February 17, 2020, contact was between Mike Lavelle, K6ML, on Mount Vaca (CM88WJ75ON) at 835 meters (2,739.5 feet) above sea level, and Oliver Barrett, KB6BA (at 1225 UTC), and Jim Moss, N9JIM (at 1250 UTC), both on Mount Umunhum (CM97BD18VJ) at 1,016 meters (3333.3 feet) above sea level. Lavell reports the dew point was –11 °C, the air temperature was 15 °C, the path loss was about 225 dB, and atmospheric loss was approximately 0.35 dB/kilometer. “CW was used, 122 GHz signals were very weak (7 dB above the noise in 22 Hz; –13 in 2500 Hz equivalent) with [fading] down to the noise floor,” Lavelle told ARRL. “Dishes were aligned on 24 GHz (71 dB above the noise) prior to [moving] to 122 GHz; we heard signals right away on 122 GHz.” The stations employed 60-centimeter satellite TV dishes and ran “somewhat less than half a milliwatt” on 122 GHz, Lavelle said.

How to Perfectly Clean Wires in Minutes!!!

Here is an old ham radio operator’s trick for cleaning wires for soldering that are old and corroded. It is hard to find this technique printed anywhere! I am a ham, NH7ZE and learned it from my elmer

(mentor). I am passing it on. I hope it helps people who need to clean wires.

8Normally, if you strip a wire, and see it is corroded, there is not much you can do to restore it's shiny new conductive properties. There is scraping and scratching which comes to mind, but you'll never get it to the solderable slickness it once was long ago. After laboring and fretting over the corroded pieces of wire for a long, long time, you see that your sweat coming out of your palms and fingers are corroding the copper AGAIN!!!! Oh, dear. NOT TO WORRY!!!!! Give yourself a pat on the back, because what you will pull out of your bag of tricks now, will send all the corroded copper wires scurrying and scampering away in fear!!!! Here is how to clean any corroded wire without even touching it, in 30 seconds!! And what's more, you can even solder it!!! This process uses two solutions, one is regular table salt and vinegar. Any kind of vinegar will work, from balsamic, to rice, to white vinegars. It’s the acidity and corrosiveness of the salt and vinegar together that you want. The other solution is Sodium Bicarbonate, or baking soda, and water. This is used to neutralize the corrosive properties of the other solution, and to further clean the wires. Step 1: Strip the wires to be cleaned. Step 2: Get 2 containers, one for each solution. They can be paper cups, plastic, glass, bowls, whatever you can find. I have vials, because I am a professional electronics installer and I use these solutions out in the field. Step 3: Get 1 tablespoon of raw salt, and put it in one of the containers. Fill up the rest of the container with vinegar, and stir the both together. As a general rule of thumb, put as much salt in the vinegar as will dissolve. Step 4: Get 1 tablespoon of Sodium Bicarbonate, (baking soda) and add it to the other container. Fill up the rest with water, and stir well. Add more baking soda to make it cloudy. The amount is not important, as long as it is alkaline to cancel the acid of the vinegar solution. Step 5: Put the stripped end of the wire in the vinegar solution, and stir the solution with the wire. any wire you want cleaned needs to be under the solution. Movement of the wire in the liquid speeds up the process. Step 6: After 2 minutes or so, the wire will look very shiny and new in the vinegar solution. The acid and salt in the solution is etching away the oxides, exposing the bare metal. Make sure the metal is uniformly shiny. Leave it in longer if it is not perfectly clean throughout. Step 7: Once the wire is satisfactorily clean, remove the wire from the vinegar, and plunge it into the baking soda solution to neutralize the acid's corrosive properties. If the wire was exposed to the air, without neutralizing the acid first, it would quickly corrode again. The baking soda keeps it clean and shiny. Swish the wire around in the baking soda water for about 10 seconds, and then you are done!! Shiny new wire ready for soldering, and conducting once again!!

9Ham Fashionistas

10Dan, KR4UB says “With the changes in field day operating power and use of generators. I think

the following article should be helpful”

A Power Line Filter for a Honda Inverter Generator

Introduction After viewing a recent ARRL youtube video regarding RF noise that can be generated by inverter based generators, I decided to do some testing of my Honda eu2200i inverter generator, a later model, slightly higher capacity unit compared to the Honda generator in the ARRL youtube video.

First Impressions The RF noise characteristics of the eu2200i unit do not seem as pronounced as demonstrated in the ARRL video, although that could be due to test configuration differences. It was noticed in the video that their antenna was very low and close to the generators. The horizontal loop and dipole antennas at home used in this testing are at an approximate 55 foot height over the test area.

• The only amateur band that had generator noise was 80 meters and was loud enough to be an issue for Field Day.

• Reducing the generator load makes a measurable reduction in radiated RF noise.

• More drastically, a shorter drop cord e.g. 20' compared to the 50' cord makes a significant

reduction.

• With a 1500 watt load at the generator connected with a 6' cord, no noise was heard on any band.

Line Filter Project

Given the club’s Field Day plans to run in a higher RF power output class with the associated higher battery draw, the two transmitters of the combined 10m/6m stations I help set up and operate will be especially demanding on the batteries. If the Honda inverter generator is to be used to recharge this station’s batteries, a fix is needed to eliminate the possibility of RF interference to nearby field day stations. The first step of the project began with a conversation with Howie, WA4PSC (www.proaudioeng.com) who stocks the Fair-Rite toroid cores, regarding the best choice of ferrite toroids. His recommendation was the Fair-Rite 4.0” OD x 1" H mix 31 units, given the frequency range at issue and will permit larger spacing between turns for less capacitive coupling. The test configuration consists of the Honda inverter generator, drop cord and the power load placed beneath my HF horizontal loop antenna located approximately 55’ overhead. It was also in the vicinity of a dipole antenna also at 55’ above ground. Noise was observed on an Elecraft K3s and a SDRPlay 1a SDR receiver both using the same antenna. All displays of received noise below are from the SDRPlay 1a SDRuno application. The generator test load is a 1500 watt electric heater, connected to the generator by a 50’ long drop cord. Several orientations of the drop cord were tried and as expected, there is an observable difference in received radiated noise based on drop cord orientation.

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Two filter configurations were tested using different toroid winding configurations, both using three of the Fair-Rite 4" OD x 3" ID x 1" L 2631814002 toroids. Toroid Configuration #1 Not knowing whether the preponderance of the Honda inverter generator noise was common mode or differential mode, the first test was with toroid #1 wound with both neutral and the hot lead in a common mode attenuation configuration and then toroids #2 & #3 used as follows. Toroid #2 was for neutral & ground, wound for differential mode attenuation and toroid #3 for the hot lead similarly wound for differential mode attenuation. This configuration was not very effective in reducing the observed noise. Toroid Configuration #2 Not satisfied with the above result, the toroids were all rewound for common mode attenuation as shown below: The hot and neutral lines are wound on two toroids "in series" and the ground wire which can also be driven by common mode noise is on a separate toroid. The "missing” (or more widely spaced turns you see in the photo below (at the top & bottom of each toroid) were required for these 4"

OD toroids to fit in the 4" deep box and permit the cover to go back on. As shown the larger 4" OD toroids permit wider spacing between the turns and thus reduce capacitive through coupling across the turns. One detail on the unfinished design here will be to bring out a ground wire stud for connection to a ground rod to be located near the generator.

12RF Noise Test Results

Using a real world 80m antenna as the test reference for radiated RF generator noise is not ideal in determining any absolute noise level reduction by the filter given the typical high 80M noise floor. But it does reflect the real world of a typical Field Day station setup. The unfiltered RF noise of the generator driving a 1500 watt load via a 50’ drop cord is shown below in the bandscope display of my SDR receiver connected to the horizontal loop antenna. The display shows the frequencies (the repeating blue bands) and correlating waves of increased noise across the noise floor of the 80m band. Using AM detector mode, the noise is audibly loud; however in LSB detection mode the noise is not audibly loud, just a higher background impulse type sound. While there were some signals on the band, only one (the orange line) was strong enough to show above the elevated noise floor.

Below is a sweep of the ambient 80m noise level without the generator running and, ironically during a widespread AC power outage that occurred February 07, 2020. The amateur radio station is powered directly by a large battery bank and the computer for this testing is on a high quality (with very low generated noise) UPS designed for the commercial market sector.

13 To illustrate the effect of generator load or lack of, on radiated nose, the 80m radiated noise shown below is with the same configuration as the first chart, i.e. the 50 foot cord attached, no filter, and no electrical load on the generator.

Finally, the noise filter effectiveness of Toroid Configuration #2 is shown below. The measurement below is with the same 1500 watt load, connected through the 50 foot drop cord, but with the filter inserted at the generator as shown on the next page. Compared to the first chart with no filtering, none of the repeating blue bands and correlating waves of increased noise are present across the 80m spectrum. No interference was found on the 40m - 10m ham bands or adjacent frequency bands. The multi-colored traces are 80m stations active during the measurement.

14Throughout the test, care was taken to keep all connected equipment and the drop cord in the same location. Earlier testing showed drop cord orientation (and of course length) can make a considerable difference in results.

Filter at the generator & 50 foot cord connecting the 1500 watt load

Final filter design

Below is the final design using toroid configuration #2, with a GFCI outlet and stud bolt connection for ground included. The stud bolt ground is connected to the GFCI electrical outlet ground and goes to the generator electrical outlet via the plug connected cable green wire. Per Honda documentation the outlet ground is internally connected to the generator frame components.

While test results show this filter to provide effective RF noise reduction with the Honda eu2200i inverter generator, other similar style inverter generators may present a different situation due to possible different power transistor technology and inverter switching rise times.

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Dan, KR4UB PostScript

A postscript is an afterthought, thought of occurring after the letter has been written and signed. In discussing this filter with a few folks the conversation tends to turn to why this or why not that. The first EMI solution that works may be expensive and certainly is not the only design solution. The filter I built works, but with the included GFCI and other parts, is a bit pricey at over $100. Would the smaller less expensive 2.4″ OD ferrites do the job? Would only two cores be sufficient? Time spent learning what others have learned is always a worthwhile endeavor in dealing with these types of questions. Howie, WA4PSC of ProAudio Engineering also passed on some excellent references for further reading. Perhaps Jim Brown K9YC’s 60 years in ham radio, vice chair of AES Standards Committee working group on EMC and extensive research in the pro audio world might yield some clues. This little 59 page “summary” is a good starting point; voilà!... that Fig 30a photo on page 23 of a design for the lower HF bands... two cores "in series" ... check! ... seven or more turns per mix 31 core... check! and choking the green wire ground...check, no out of sequence turns on the core.. check! Jim’s other publications can be found here.

I used to ask during my working days while dealing with difficult EMI problems, “where is that magic purple lens” made of dilithium crystals (you know the stuff in StarTrek that permits faster than light warp drive) and permits you to see the pesky RF energy leaking out so you know exactly where and what size band-aid to use. Never found it!

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The Link Classified

For Sale

Craftsman 3 HP 12 gallon Air Compressor $ 50 Craftsman 4.5 HP 20 gallon Air Compressor $ 75 Microwave Oven 700 watt – Dorm Room Special $ 50

Contact Charlie, NC4CD at 919-602-5200

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

If you have items to buy or sell, send your ad to: Martin, KA5JUJ

martin@brody1.com 919-260-0632

16Minutes of Last Club Meeting

Durham FM Association (DFMA) DFMA Meeting – 02/04/2020 – Dan, KR4UB, Secretary Location: Bullock’s Bar-B-Cue, Durham Attending: WB4ROI, Henry; NA4VY, Dave; W4SAR, Dave; KD4YJZ, Karen; KN4SVO, John; KV4ZR, Loren; KA5JUJ, Martin; N2XZF, Paul; KR4UB, Dan; N8BR, Bill; W4BOH, Wilson; KW4XL, David & David Jr.; WA4UJM; Wally; KN4ZBS, Kevin; KM4MBG, Jack; KF4PAB, Lenore; KN4FKH, Felicia; KD4WNZ, Bill; KE4JYJ, Sue; KM4LKN, Detlev; W4OFZ, Banks; KE4QOZ, Joanna; KE4HIH, Rhett; AJ2X, Mark; KF4LJZ, Linda; KA4AVM, Sue; WB4YYY, Jim; W4PEL, Pete; K4BCK, Becky, K4VO, Bob; KN4PTU, Charles; KW4KZ, Chuck; Guest: John Book, Jr.

A total of 34 attending, with 32 being currently licensed hams.

President: Jack, KM4MBG opened the membership meeting at 7 pm with introductions, followed by announcements.

First time attendee was KN4ZBS, Kevin whose interests are radios in general, emergency services and hurricane disaster relief.

Announcements:

Jack, KM4MBG circulated a get well card for all to sign for Jimmy, KF4KFU who has been ill for some time.

REPORTS

Vice President – Jimmy, KF4KHU is absent due to illness. Treasurer – Lenore, KF4PAB provided the treasurer’s report. Beginning with the new year - 29 members dues are current.

Secretary – Dan, KR4UB announced that the Field Day sign-up process, which began last year as an experiment will be repeated for 2020 Field Day. The idea came from feedback and discussion with several new members expressing that arriving at Field Day without some prior preparation and knowing who to contact can be a bit intimidating. A new ham may not know what they would like to be involved in, in part due to not knowing what Field Day activities are actually available for their participation. The sign up listing provides a view of the key tasks, stations/modes to be operated, set up and tear down activities giving new hams a view of possible involvement areas and who to contact beforehand.

Dan recognized John Cowan, KN4SVO for his awesome participation in Field Day last year, as an example of what early conversations prior to Field Day can help facilitate. John took on a major role with ground rod installation, participation in tower raising, operating FT-8 and setting up his own laptop with FT-8 at Field Day for future use.

Dan circulated the participant listing from last year, along with new sign up sheets to begin the process for 2020.

17Repeater Manager – Charlie, NC4CD absent, no report.

AuxComm EC – Shawn, K4CTD absent. Charles, KN4PTU discussed the recent auxcomm meeting at the Durham EOC and summarized the excellent training available to interested hams, some of which will pay participants per diem to cover expenses of attending. Available training includes Satcom, NVIS, ALE & HF communications methods.

New Business – Jack, KM4MBG opened a discussion on the DFMA MCU or Mobile Communications Unit. The MCU is being used for only two events of the year, DurHamFest and at the combined OCRA/DFMA Field Day.

The MCU presents not only a financial cost to the club, but also a human cost in that ongoing maintenance that must be done by a few willing volunteers to keep the vehicle in running condition and prevent weather exposure from doing irreparable damage to the vehicle. The objective of the discussion was to solicit from the membership possible options regarding the future of the MCU. Discussion points presented by the membership were as follows:

• Donate the vehicle, minus all usable radios and equipment that could be repurposed; as ability to

realize any significant monetary return given its age is minimal. • Donate usable radios and equipment to Durham EOC if needed; follow up comments indicated a

fair amount of what is needed at the EOC is already there. • What is the annual financial cost of maintaining the vehicle? (Lenore … I think I heard about

$1000 / year.. Please update) • A Field Day alternative to the MCU must be found before considering disposal. Wide spread

membership comments support this position. • Replace it with a cargo trailer which will not have the “running works” maintenance overhead;

however this would create a dependency on some club member having a suitable size truck to tow the trailer and be willing to volunteer when needed.

• While the MCU is owned by DFMA, input from the OCRA club should be solicited. • <humor on!> Donate the MCU to a library for use as a bookmobile! </humor off!> it’s former role in

life! • Wilson recounted history when the MCU was first acquired and made some significant

observations. o When first acquired by the club, 14 people promised to help with the vehicle, 2 showed up. o It does serve a useful purpose, has new tires, it is functional although could use a

mechanic’s check out. o It is nice for field day. o Some of the installed radios actually belong to Charlie, NC4CD o Equipped with a 7.5kW generator, air conditioning; he considers $1000/year maintenance a

reasonable expenditure for the club. • Dan, KR4UB commented the MCU presents two fundamental issues that need resolution

o Covered storage must be found for the MCU to arrest continuing deterioration and minimizing the maintenance issues

o More members must volunteer to help with the maintenance so it no longer falls on 1 or 2 individuals.

On the last point, Dan solicited for volunteers to help. Most recent maintenance work has been carried out by Wilson, W4BOH and Dan, KR4UB. The following members volunteered to join in on the maintenance, with a major clean up and inspection of the MCU to be scheduled in the March/April time frame as the weather turns warmer.

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• John, KN4SVO • Loren, KV4ZR • Wally, WA4UJM • Chuck, KW4KZ

On that final note with a suitable size crew available to turn the maintenance burden into a work session social event complete with HAM (have another meal) accoutrements Wilson, W4BOH declared the grill will be open with hamburgers at the end of the work.

DurHamFest – Dee, KU4GC was unable to attend. Jack reminded all that DurhamFest is on May 30th, a rather infrequent 5th Saturday occurring in May. Field Day & VE Coordinator - Dave, W4SAR led a brief discussion of the plans to run higher RF power for Field Day this year. This should make it easier for the voice stations to make contacts and for the CW stations to hold and run on frequencies making more contacts. CW & digital contacts will have a 2x versus a 5x score multiplier. Other considerations are the need for higher power rated band pass filters, the increased power demand on batteries and preparation for recharging batteries during Field Day using fossil fuel generators permitted for this Field Day class.

The next VE test session will be held at the Efland Baha’i Center on Saturday, February 8th at 10am.

Elections will be held at the next OCRA monthly meeting on February 10th at the Efland Baha’i Center. Dave indicated that he will no longer fill in for the vacant secretary position, which has been open for the last two years and, not continue to serve as president with critical board positions open.

Presentation of the DMFA “Lid” Award - The DFMA LID was last presented by Jack, KM4MBG to Jimmy, KF4KHU for his generous gift to the club of the new Optoma projector and, for his IT work to upgrade and maintain the DFMA website. Door Prizes - Door prize winners selected from the attendee sign in sheet by a random number generator program were as follows: Multimeter - John, KN4SVO; Magnetic Pick up Tool - Sue, KA4AVM; Flashlight - Henry, WB4ROI; and a free calendar from Dan, KR4UB - Karen, KD4YJZ.

Program: The program presentation by Jack, KM4MBG on Software Defined Radios. Jack started out with a comparison of analog versus software defined radios. The analog radio uses fixed, physical components to perform much of the function compared to an SDR radio that converts the RF signal in the early stages of the radio, then using software algorithms to perform much of the tuning, filtering, demodulation and display of the received signals. The SDR performs this function by interpreting the incoming signal not as a two dimensional (cartesian or x/y coordinate system ) signal, but as an “I/Q” format or more precisely a “phase vector” in a polar coordinate system. The signal viewed in this manner can appear as a helix or spiral in three dimensions, giving much more information about the signal. http://whiteboard.ping.se/SDR/IQ It turns out that the mathematics of solving certain problems, whether to be solved by a human, or by a digital signal processor algorithm can be easier to solve by choosing a coordinate system most suited to the the problem at hand. Just as we describe impedance in a circuit or transmission line as having a real (resistive) and imaginary (reactive) component due to the effects of capacitance and inductance, or use a Smith Chart for solving impedance problems, the I/Q format (a polar coordinate system) best describes sine wave like signals as a rotating vector moving in space. For the SDR this actually lowers the computational processing workload to do whatever, to make a filter, demodulate, and so on, and opens the door to much more sophisticated signal processing function. As Jack showed in the presentation, an SDR FM receiver can be “built” stringing

19together blocks of mathematical function working as a sampler, low pass filter, a quadrature decoder, audio or whatever is needed. https://www.rtl-sdr.com/tutorial-creating-fm-receiver-gnuradio-rtl-sdr/

Jack went on to briefly discuss a number of SDRs available ranging from low cost, limited function to more costly systems. They are listed here.

• RTL-SDR.com • Raspberry PI RTL-SDR Scanner • HackRF One from Great Scott Gadgets • SDRplay Product Line • LimeSDR

Jack completed the presentation with the announcement that the 10th Annual GNU Radio Project Conference will be held in Charlotte September 14-18, 2020. More information is available at the following URL. https://www.gnuradio.org/grcon/grcon20/ Meeting adjourned at 8:20 pm.

Minutes of Last Board Meeting Durham FM Association (DFMA)

DFMA Board Minutes – 02/18/2020 – Dan, KR4UB, Secretary

Location: 1920 Front Street, Durham

Attending: (y) Jack, KM4MBG - president; (n) Jimmy, KF4KHU - vice president; (y) Lenore, KF4PAB - treasurer; (y) Dan, KR4UB - secretary; (y) Charlie, NC4CD - repeater mgr; (n) Shawn, K4CTD - AuxComm; (y) Dee, KU4GC - DurHamFest chair ; (y) Dave, W4SAR - Field Day; (y) Martin, KA5JUJ Link Editor; At-Large Board Members: (y) David, KW4XL; (y) Paul, N2XZF; (y) Chuck, KW4KZ; (y) Karen, KD4YJZ. President – Jack, KM4MBG called the meeting to order at 7 pm with the call for officer reports.

REPORTS:

President - Jack, KM4MBG relayed a report from Sam, KJ4VWG that the APRS node at the Durham EOC is off-line. Jack further indicated that since some equipment at that location has previously been damaged from lightning, an inspection of the site the radio equipment and antenna grounding should be done. He will get in contact with Steve, W3AHL about the possibility of such an inspection.

Vice President – Jimmy, KF4KHU unable to attend. Jack, KM4MBG filling in for Jimmy needs leads on presentations. No presentations are scheduled for March yet. Jack asked all board members to explore ideas and possible contacts that might do a presentation. Dan, KR4UB will contact Nick England about a possible presentation on his Naval Communication Station equipment collection and the Navy’s use of HF communications.

Treasurer – Lenore, KF4PAB provided the treasurer’s report. There are 56 members with dues current.

Secretary – Dan, KR4UB - The minutes for the 02/04/20 Club Meeting was approved.

20 Repeater Manager – Charlie, NC4CD reported the new 6m repeater antenna from fmbroadcastantenna.com has been received. It will go on a pipe mount atop the TV Hill tower. Paul is making progress on the RF deck. Discussion continued that a duplexer offering better performance would be desirable. Dan, KR4UB suggested that Charlie contact Tom Brown N4TAB to determine if the 12 cavity helical resonator duplexers that Tom provided for the 6M OCRA repeater many years ago are still available. Lastly Charlie reported that a power drop at the Hillsborough site resulted in the repeater DVR voice recordings to be lost. A new technology DVR has been procured and the voice recordings will be reloaded. Auxcomm – Shawn, K4CTD unable to attend. Charlie, NC4CD attended the last EOC meeting and summarized Gregg Houser’s presentation on the training available state-wide. ICS 100, 200, 700, 800 and a 3 day training course are the required current training levels. DurhamFest – Dee, KU4GC DurHamFest Chair gave a progress report for the 2020 event. The DurHamFest Flyer is complete, the insurance binder has been obtained, event information has been submitted to RARS for publication and event registered with the ARRL. Volunteer roles are expected for the most part to be the same as last year. Volunteer confirmation received so far include Lenore, KF4PAB - ticket sales, JoAnna, KE4QOZ - club table, Dee, KU4GC - food logistics; Wilson, W4BOH - cooking, David, KW4XL & Felicia, KN4FKH food preparation; Jack, KM4MBG - donuts; VE Session - Dave, W4SAR will be out of town but will prepare the session paperwork, Paul, N2XZF & Dan, KR4UB signed up as volunteer examiners; Dan, KR4UB - transportation of Hoover Rd items (tables, canopy, ticket drum, ice coolers, signage) for DurHamFest. Dan reported new handicap parking signs are needed. Dave KX4XL volunteered to print and laminate new signs. MCU cleanup and drive to site - the new MCU volunteer committee. Contact and confirmation with the remaining volunteer positions is in progress. Field Day Coordinator - Dave, W4SAR reported contact is in progress with the Field Day captains to confirm plans to run the Field Day class permitting up to 150 watts, on battery power. Charlie, NC4CD motioned that DFMA share in the cost of new band pass filters for the higher power class and recommends suitable filters such as those available at DX Engineering be purchased. NEW Business: Follow up discussion on the MCU was as follows:

• The consensus from the last DFMA club meeting and OCRA meeting is that the MCU serves a worthy purpose and steps should be taken to preserve it and keep it maintained.

• Lenore summarized the MCU costs for the past 4 years, and averages $1070.00 per year. • The following new MCU volunteers are a significant addition to the maintenance team and a very

positive development. o John, KN4SVO o Loren, KV4ZR o Wally, WA4UJM o Chuck, KW4KZ

• A major clean up and inspection of the MCU by the team will be scheduled in the March/April time frame as the weather turns warmer in preparation for its use at DurHamFest and at Field Day.

• A board discussion on a suitable storage shelter for the MCU yielded the following: o Given the current plan for a new building to be located at TV Hill to replace the

Hoover Rd storage building, the question was posed to Charlie, NC4CD whether a

21larger building that could house the MCU at the TV Hill site would be possible. Charlie offered that a larger building would be acceptable at the site.

o Dan, KR4UB having maintained a similar sized motorhome for many years recommended a fully closed in building not only for sheltering from rain but also to prevent dew-point condensation occurring in humid weather that coats with water all the heavy, expensive steel components underneath the vehicle. Over time this causes expensive and damaging corrosion.

o Charlie similarly recommends a fully enclosed building to provide the needed security at the site.

• The board requested that Charlie, NC4CD investigate the cost for a Leonard steel frame metal, fully enclosed building suitably sized to store the MCU.

Lenore, KF4PAB proposed to the board a change to the membership dues payment model that will ease the treasurer’s workload, and also offer more flexibility to the members in the payment of their dues. The change would be to go to a “rolling subscription model” for dues payment that works the same way as any magazine subscription and is the same model that OCRA club adopted some years back. Lenore will propose and provide additional detail to the membership at the next meeting on the proposed change. Jack, KM4MBG brought up an idea for a club special interest group that arose from discussion at one of the Saturday morning breakfast meetings. The interest group would focus on computers for ham related use, and non ham general computer use at home, and fostering learning in a group environment above and beyond what one is likely or afraid to tackle on their own. It could be learning more from fellow hams about migrating from a Windows OS to a Linux OS, or learning how to use a Raspberry PI for some special ham or home related purpose. Given that inexpensive desktop and laptop computers are frequently available at hamfests, acquiring an additional computer for learning purposes or new project takes the risks out of modifying an existing computer in use. In the application development world of commercial IT this is referred to as a “sandbox” machine. For many of us the thought of tackling such a project alone is too intimidating and we tend to shy away. That special ham shack project, or learning to use a new operating system or specialized application would be easier for an interested individual member in a group learning environment. Given the club’s talent base, it’s highly likely another member already possesses the skills and is willing to help others gain experience in a new area. Charlie, NC4D brought up that interest has been expressed in a “Wives/Significant Others” meeting for dinner, possibly at Bullocks on the same night as the DFMA meeting. Dee, KU4GC reported there is a private meeting room at the opposite end of Bullocks that could possibly be used for this purpose. Dee will check with Bullock’s and if available, the topic will be brought up for discussion at the next club meeting. The meeting was adjourned at 8:00 pm.