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

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!

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!