Sunday, April 9, 2023

The QDX + QCX-Mini at K-3036

Easter weekend gave us a little bit of time to hang out with out family, but the weather was not very cooperative. Saturday proved to be the best weather-wise, we we headed out late to the nearest state park, Martin Creek Lake. When we arrived, my wife and the kids began rigging up fishing poles, while I started throwing lines up in the trees.

With the help of my daughter's boyfriend's pitching arm, we managed to get the end of my 20m EFHW about 25 feet up in a pine tree. I wasn't sure if it would be good enough for 5w, but a few minutes on the air proved my worry was misplaced.

I broke out my 20-Meter QCX-mini, hooked everything up and called CW POTA. Instantly, KD3D came back to me. This being my first true CW activation, I stumbled quite a bit over the callsigns. I blame it on a mixture of nerves and a lingering lack of confidence in my CW skills. But as they say, 'experience is the best teacher!' (At least I'm sayin' it.) 

Soon I had stations calling on top of each other! Wow! Within about 15 minutes I had managed to pick out 12 stations and I was pumped! The sun was about to set and I knew I wanted to try my QDX as well, so I packed the QCX-Mini and

Monday, March 27, 2023

RF Chokes and my NanoVNA

Spent some time last week working with my NanoVNA. I've had the VNA for a couple of years now  but used it mostly for checking SWR on my antennas. It's the 4-inch screen model, which is easier on the eyes but still small enough to throw in my go-bag. 

I've had a few issues with RF in the shack causing some interference. I use a multi-band vertical and an 80-meter dipole as my primary antennas. The vertical is prone to producing some RF on the coax so I built a couple of chokes to help eliminate the problem. After watching some YouTube videos on using the NanoVNA properly (I really like Barry's videos - , I was thrilled to be able to measure the signal loss on each choke.

I started by building a testing jig which allowed me to use the "Through" function of the VNA with a choke inline. I cut a set of alligator clips to use with it and wrapped it all in heavy-duty shrink wrap to protect it. My "Ugly Balun" choke was fair. Probably enough to be ok at the lowest frequencies, but not efficient higher up the dial. I then built a choke with RG-316 coax and a 140-43 toroid. This one was much better across the band. I took the opportunity to also install my grounding box with lightening arrestors at the same time. 

Monday, February 20, 2023

Testing out the new QDX GoBox

(UPDATE AT END) I love QRP Lab's stuff and and I've really enjoyed the QDX! I recently took my QDX and built it into a weather-resistant case I picked up at Harbor Freight. I used marine-grade HDPE plastic to create a panel that fit in the lid of the box. The box happened to have small cylinders in each of the corners, so I used by tap kit and cut some threads in them for screws. Then I mounted the QDX, a RaspberryPi-4 computer and 7-inch HMDI screen that runs on 12 volts. I routed all the wires behind the panel and down to the box. 

For the time being, I'm using pull-apart foam to hold things in place but I'm considering a more permanent panel in the bottom as well. Using a 6-amp/hour LiFePO4 battery, I powered everything in the box. The Pi and the screen run on a USB plug connected to the battery and the QDX runs at 12v via a buck converter to keep the voltage from spiking and risk blowing the power transistors. 

Stations which heard by signal on 30m
I took the setup to my local park and hung my End-Fed-Half-Wave (EFHW) multi-band antenna in a tree and configured it for 40 meters. I fired up WSJT-X and almost instantly I was decoding FT8 stations. I made a few contacts before switching to 10 Mhz. Fortunately, 30 meters was HOT with station consistently loud across the band. I then switched to JS8Call and, again, there were lots of stations. I sent a heartbeat and got a dozen responses. Sadly, I called CQ for about 15 minutes with no takers. 

Still, I seemed to be getting out nicely, especially according to PSKReporter. With the sun starting to set, I packed things up nd headed to the house. All in all, I am very pleased with the rig and the whole setup. Now I'm looking forward additional trips out into the wild!

UPDATE: I have now fried TWO Raspberry Pi 4Bs using my setup. There was no obvious reason why, but both times, when I turned the system on, the Pi got VERY hot and smelled like it was burning. After disconnecting and trying again, the Pis were dead. After a discussion on the Pi Community Forum ( I decided to remove the overvoltage diode on each Pi and...BAM...they worked again. However, they are no longer protected from overvoltage. I've ordered some replacement diodes to repair the boards. 

As far as why, the only thing I can guess is that the "Quick Charge" USB socket misunderstood the Pi and thought it wanted more than 5v. They can deliver up to 24v at times. Another possibility is that the HDMI screen, powered by the battery as well, may have back-fed some power on the HDMI port, helping to trigger the USB socket. So, I've decided to replace the USB sockets with 12v-in-5v-out buck converters to ensure the Pi only get 5 volts. 

Stations which heard by signal on 40m

Monday, January 16, 2023

Improving the QCX-mini power

I recently built my second QCX-Mini, this one for 20 meters. It's such a fun a build and even more of a joy to operate. I took it out to my local park for a test run using my homebrew, end-feed, half-wave, multi-band antenna. When the radio came on, the band filled with signals from a CW contest. I tried to respond to a few station, but apparently no one could hear me. I texted a friend who lives nearby and he was able flip on his HF radio and verify that I was indeed getting out. 

Back at the house, I pulled up Hans' video on maximizing output power on the QCX and sat at my bench to work on mine. I hooked it up to an RF power meter and found my rig was putting out a whopping 1/2 watt. No wonder no one could hear me. 

I adjusted the L3 inductor by spreading out the windings and managed to get right at 4 watts. But regardless of how much more I worked with it and the other two inductors, 4 watts was the most I could get. So, following Hans' advice, I desoldered the inductor and remove two windings. Once I soldered it back on the board I was able to get just over 6 watts. Perfect! I closed up the radio and packed it in the bag. 

This weekend, I took it back out to the park. Again--being a Saturday--the band was jammed packed with contest signals. However, this time, after waiting for a pause in an exchange, I called a station sending CQ. Instantly he returned my call! I gave him the exchange and he sent, "TU." It worked! I had about an hour of daylight left, but I wound up with 14 QSOs, all of them solid exchanges. 

Sunday, January 1, 2023

TinyPaddles are a HUGE deal!

As the Christmas holidays approached, I decided to give myself a small and inexpensive gift...a new set of paddles. Mind you, these aren't just any set up paddles. These are a SUPER tiny micro-paddles! Called the "TinyPaddle," they were designed built by N6ARA. You can buy a kit version, but I opted for the assembled set. I first saw these on Tom Witherspoon's (K4SWL) site, I finally ordered a set just before Christmas and they arrived before New Years.

These are indeed very small! The paddles are soldered onto a circuit board and the board is insterted into a 3D-printed holder. The assembled version comes with a case which is basically a 3D-printed sleeve to protect the paddles when stowed. I also ordered the cable. The both came with an adjustment tool to carefully bend the paddles in or out as a way of adjusting the feel of the paddles. He also sells a version with the male plug instead of the female jack, in case that fits your setup better.

After playing with them for a little bit, I have to say I really like them! No, they don't feel like a $200 set of paddles. But, then they only cost $24! They are perfect for backpacking, POTA (my use), SOTA (not in Texas!) or any other ultralight station bag. I'm a sucker for cool, lightweight, micro gadgets and these certainly fit the bill!

Friday, December 30, 2022

Quick POTA trip with friends

Don (the ham who inspired me to get back into CW) asked at the last club meeting if I wanted to activate our local state park over the holiday break. Since both of us work for school districts, he knew I'd have a little spare time during Christmas. I said, "of course!" and that led to a fun Friday morning last week at Martian Creek State Park, just south of Tatum, Tx.

Don also invited a few friends from the Longview Club (LETARC) who got there early in the morning. In total, there were four stations on the air at some point during the day including two on SSB and two on CW. It was Don's first official outing with his BuddiHex. It was an impressive site to see the spider-web antenna hoisted high in the trees! He racked up 40+ POTA contacts within the first hour or so and seemed to created a pile-up every time he keyed the mic!

I took my new 20-meter QCX-mini for its first time in the wild. I paired it with my homebrew ENHW multi-band antenna. My wife tagged along as well. She got a new fishing rod and a Solo Stove for Christmas and spent time breaking in both along the shore of the lake.

Wednesday, December 14, 2022

A new LiFePO4 charger

I'm in love with LiFePO4 batteries. They are lightweight, powerful, and last forever (if you count 2000+ cycles forever). I have a several that I use with various radios and other projects.

What I don't have is several chargers. The charges tend to be very expensive, especially ones with higher amperage. The first one I received as part of a deal when I bought by first battery. Since then, I've looked for cheaper chargers with little success.

I recently found one on Amazon that was around $20 and sometimes even had a coupon. I ordered and, so far, am pleased with it. It's only 3-amps so I'm not going to be charging my larger batteries with it, but it seems to work very well with my 6 and 10-amp batteries.

LiFePO4 Battery Charger

All my equipment has Anderson Powerpoles installed (a ham radio and emergency radio standard), so, as you can se in the pictures, I clipped off the RC connector and installed powerpoles. This way, it mates easily to all my batteries and my power boxes.

I hook it up to a 6-amp battery along with a power monitor and watched it top off the battery. Once it got to 14.7V, the charger ramped down the power and turned itself off. We'll use it over the coming weeks and see how it fares.