Many thanks to Sam (WN5C) who shares the following guest post:

Notes from a homebrew POTA adventure

Sam (WN5C)

I recently wrote about the homebrew transceiver I built to operate on a month-long trip through the American Southwest. Upon arriving back in Oklahoma here’s the final outcome: 27 days, 40 parks, and 669 QSOs. I honestly can’t believe that the rig went the distance, or that I made so many contacts on 2 watts or less!

The priority of this trip wasn’t radio, though. I’m an archaeologist and I’m starting a new research project that marries my historical interests with my love of two-way communication. In short, I’m studying the effects of how communication technology aided the American colonization and transformation of the western United States around the turn of the twentieth century. This means I walked and mapped single-wire telephone lines strung up in pine trees in northern New Mexico (used to connect fire lookouts with Forest Service ranger stations), a fascinating story of dramatic changes in land management. I also visited heliograph (sun-mirror signaling) stations established in southeastern Arizona by the U.S. Army Signal Corps in 1886 to assist in apprehending Geronimo.

Working Fort Bowie NHS (US-0815) in Arizona. The peak in the distance, Helen’s Dome, had a heliograph station on top. From the fort telegraph lines would have connected remote operations to the rest of the Army’s 1880s communication network. Next time I’m climbing up on top!

I look forward to relocating and studying the artifacts from more of these heliograph sites (mostly on remote peaks) to reconstruct this communication network and understand the lives of both the soldiers and the Apache, and how this novel surveillance system altered the battlefield. Based on the artifacts I’ve seen so far there are many cans of Army-issued proto-Spam and beer bottles surrounding the signaling station where American Morse Code would have been sent and received via flashes of sunlight. The original Field Day?

But back to radio. I covered a lot of ground and activated parks in Oklahoma, Texas, New Mexico, Arizona, Utah, Colorado, and Kansas.

The POTA sites that I activated (click image to enlarge).

At some locations I was camping so I was able to do multiple long activations and work the lower bands well into the evening. These were some of my favorite moments of the trip, being the only spot on the POTA app and leisurely working with no time or weather-based worries. It also gave me a chance to hear callsigns I was unfamiliar with, essentially exploring a new area of the country.

Working closer states after hours on 30 and 40 meters at Colorado NM (US-0918).

For other times, due to time constraints or weather (thunderstorms or that it was unbearably hot), I got my 10 contacts and moved on. Sometimes I packed the equipment for a long hike, often carried it from the car to a picnic table, and a few times deployed my antenna and operated from my vehicle.

Not every activation was a grand adventure. Sometimes, like here at Rocky Mountain Arsenal NWR (US-0226) in Colorado, I worked from the passenger seat in the car.

Every activation was memorable in its own way. I worked folks from 44 states, five Canadian provinces, and an unforgettable contact from Italy.

A map of the contacts I made (not including those in northern British Columbia, Alaska, and Italy).

The radio held up surprisingly well. Aside from it looking like a Dalí painting as the 3D printed box continued to deform in the heat, and some hot glue remelting, the electronic components worked as they should. I look forward to printing a stronger case and making some upgrades going into the fall. I do now have a real respect for the engineering that goes into designing field radios, especially those that are thrown into a pack!

Setting up a portable shack on Vail Pass in the White River NF in Colorado (US-4410). This was near the end of the trip, the plastic case was looking pretty bad.

After I began feeling less anxious about the homebrew radio (it kept turning on!) I could start focusing on the trip itself: an amazing POTA adventure with an often-uncooperative sun. Here’s a few themes I noted. Continue reading WN5C: Notes from a homebrew POTA adventure →

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. Continue reading →