Sam’s Thunderbird Mk 1 Takes Flight: A Homebrew Radio Field Report from the American Southwest

Many thanks to Sam (WN5C) for sharing the following guest post:

Homebrew in the Field

by Sam (WN5C)

What a week it’s been!

I have the opportunity to spend a month traveling through and camping in the American Southwest (specifically, New Mexico, Arizona, and Colorado) doing archaeological work. And of course, that means the prospect to operate portable at weird times and in lots of places.

I’ve been planning for this trip for a couple of months, about the same length of time that I’ve been trying to achieve my amateur radio dream: to build a complete transceiver. So why not try to do both things at once?

This is just a quick note of my experiences in the first quarter of my trip of taking a homebrew rig into the field.

First off, I have absolutely no background in RF engineering, or electronics at all. But the literature is good and Elmers are priceless (thanks Kenn KA5KXW!). I started small, with kit projects, and then very basic transmitters.

I’ve always appreciated how much satisfaction my father gets by building things by hand, and finally I have a similar hobby. I called the radio I designed the Thunderbird Mk 1 based off the fact that I cut my CW and POTA teeth at Lake Thunderbird State Park in Oklahoma and will probably continue to work there the most. It’s a 6-band (40, 30, 20, 17, 15, 10) CW QRP transceiver with SSB receive.

The receiver is direct conversion and is an amalgamation of VU2ESE’s DC40, KK7B’s Classic 40, and W7EL’s Optimized QRP Transceiver. The VFO is an Arduino/si5351 combo based on the schematics and code written by VK3HN (who has helped me from afar, thanks Paul!). It’s crude, but I use a 6-position rotary switch to manually switch between the band-pass filters.

The transmitter is based on W7ZOI’s Updated Universal QRP Transmitter, married with VK3HN’s Arduino code that acts as the oscillator, keyer, and side tone generator. I get about 3 watts output for 40, 30, 20, a little less for 17 and 15, and about a watt on 10 meters. Like the receiver, I manually switch the low-pass filters.

Here’s a picture of the digital parts (ignore the second Arduino Nano, I thought I would need it but did not), the power board, and the filters. It’s on the bottom:

On top is the main board with the receiver, the transmitter, and T/R switching. Also, you’ll notice the green PCB. I *really* wanted to build NM0S’s Hi-Per-Mite from scratch but I couldn’t get the circuit to run right before my trip so I opted to install one that I built from a kit. It’s a fantastic CW audio filter that I can switch in and out (everyone should have at least one!).

I can switch in a little speaker and added a straight key jack. I printed the box on a 3D printer at the local library. It works great for the shack. In the sun, it’s starting to warp in the heat, so I’ll have to address this, but things still work!

Getting out the door on time with a finished radio was tough! I had finished right before I left on my trip (end of May 2024) and had no time to field test. The best I got was taking the rig to the table in the back yard and firing it up during the WPX contest.

I made amazing DX contacts on all the contest bands I had and called it good. But working superstations isn’t real life, and over the next week I’ve had to MacGyver the radio (rigging a car jump pack, an inverter, and a soldering station together at a picnic table to replace a bad transistor, for example). I think I’ve finally shaken out (literally) all of the loose solder joints and bad grounding.

But it works!

In the first week I’ve activated nine unique parks and have over 200 QSOs. I hope to shoot for 30 parks by the end of June, and cap my time by working Field Day. I use a random wire and an ATU-10 at camp, and a JPC-12 in the field (sometimes just using a 17-foot whip and the base for 20 meters). The vertical is quick to deploy and necessary out here where there aren’t always tall trees.

I always have the ATU-10 with me as a gauge that things are working properly. Of course, my second day in the field I thought my radio completely broke as I couldn’t even hear FT8 on any band, but a quick text back home let me know that the solar conditions really were that bad!

Besides 10 meters, I’ve had luck on all bands even with my meager output. And, the SSB receive has been really nice. It’s both entertaining and comforting to fall asleep to nets on 40 meters in the tent, and listen to the VKs and ZLs roll in on 20 meters late at night.

I’ve been to some neat places. I’m currently on the side of a mountain at 9,200 feet with a random wire 40 feet in an aspen. It’s been fun to work local states in the evening hours on 30 and 40 meters. Here I am working 20 meters at one of the old fire lookouts in the Jemez Mountains of New Mexico. The post would have held the map board for rangers to sight and call the fire in.

And here is the radio along the Rio Grande Gorge in Rio Grande del Norte National Monument in New Mexico:

Hopefully the radio holds together for the next three weeks! I’ve had the opportunity to operate on and off quite a bit when I get off of work, so I hope to hear you!

I’ll be traveling through a bunch of different parks at different times. If you have called me back, thank you! You might observe that I ask for a lot of repeats. The reason for this is that while W7ZOI’s T/R relay switching is fantastic it also provides a fraction of a second delay and sometimes it’s hard to catch the first letter of your call. Everyone has been understanding though.

Hope to hear you on the air!

12 thoughts on “Sam’s Thunderbird Mk 1 Takes Flight: A Homebrew Radio Field Report from the American Southwest”

  1. I’ve never built anything like that before, but reading this made me remember from the 60s when I was a kid, an article in Popular Electronics (?) about a complete 80m CW transceiver. It had lots of miniature tubes and a crystal socket for easy frequency changes. I dreamed about putting it in an attache case like the illustration in the article and pretending to be a spy. I also remember long sessions with the Allied catalog pricing out all those tubes. The closest I come to looking like a spy is that I do wear a Fedora. Maybe someday I’ll get really motivated and do it!

    Good luck on your adventures 🙂

    Ken, KA8VLW, Michigan

    1. I know I am dating myself by saying how much I loved the Thunderbirds!

      This is another one of those thousand and one reasons why ham radio is so cool. Want to buy off the shelf? Go for it. Want to source it yourself? You can do that. Want something in between with a kit to assemble? Plenty available.

      In the end, they all send out a signal and that’s what we’re all about. Well done!

      David W7CDT

  2. Oh, what nice work, Sam! Bravo!
    It’s been a while since I homebrewed anything that ambitious, but I can recognize the time and effort that went into the making, and rejoice with you over those sweetest words to the homebrewer’s ear; “But it works!” !

    3D printing is one of the no-joke miracles of the 21st century, but the process does leave a lot of residual stresses locked up in the material, which are released when heated to a softening point. Soften it enough (say in boiling water) and the result can be remarkable! Haven’t figured out a solution, unfortunately, so I hope your warping problem stays within workable limits.

    Many thanks for this article, with all the interesting details and humor!

  3. Thanks Thomas for posting! Here’s a quick update at about 2.5 weeks into the trip:

    I now have 21 unique parks and about 400 QSOs, and things are still working well. I’m mostly working 20 meters for quick activations as I’m currently in southern Arizona and things get hot!

  4. Terrific adventure and gud- on-ya mate for trying science without a science background. I actually re- read Tony Fosters “Sacred Places” this morning. He is a minimalist painter/adventurer and carried a self developed large watercolor system to paint some terrific work from the area you are traveling thru. His wealthy patrons built a fantastic museum not far from me in Palo Alto California. You can see some of his art on the WEB. Stay safe and 73’s

  5. Congratulations! Great job! Working on a homemade radio is a great pleasure and an incomparable feeling! When I made my first radio, I was forced to restore bad soldering and fallen parts several times, but then everything worked perfectly for many years. The only drawback of a direct conversion receiver is interference from broadcast stations. In return you get fantastic sound!

  6. Very cool and a great job. Obviously, you are having a great time. It’s been many years since I have homebrewed RX/TX equipment, at this point kits are more my style. While I still get significant satisfaction from kits (just finished a QRP Labs QMX+ and have built an Elecraft K2, M0NKA’s mcHF and a (TR)usdx), it’s not the same as a true homebrew job…

  7. Well done , like you all my outdoor activities are conducted will homebrew transceivers and antennas (vertical and VDA). The pleasure to use its own equipment is great providing the same performances compare to commercial equipment with spending thousands of USD . Homebrewing is not an activity from the past for sure.

  8. Bravo on getting the homebrew on the air for extended field operations. That’s no small accomplishment.

    And thanks to you and all who document their experiences here. The shared knowledge is a benefit to the whole community.

    72 de W6CSN

  9. I had a QSO with Sam recently where I was running 500 milliwatts and he was able to hear me in the park he was activating 758 miles away (1,516 miles per watt). I would say he did a very good job with the receiver in his Thunderbird MK1. Excellent work Sam.

  10. Sam, congrats on your CW trek thru the Southwest. I connected with you a couple of times. I hope you’ll give us a summary of your journey with photos of your radio activity and maybe your archaeological activities. Thanks for being out there.

    Randy, N5ILQ

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