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

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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!