Enjoying The Fruits of My Labor

 

As many of you know, most of my portable operating is done via a bicycle.  When I discovered the QRP Labs QCX Mini series it was like the heavens opened up for my QRP portable operating. For years I've used my Yaesu FT-817 for portable operating especially while doing my bike touring activities.  The FT-817 provided multi-mode options but during my bike tours the unit and accessories took up a lot of space in my panniers.  So the QCX Mini rigs are the perfect portable rigs for my CW and bike touring activities.

I opted to order a 40 meter QCX Mini kit. The backlog for an assembled units was too long for my liking so why not put my ham radio skills to work and build this unit. I completed my unit in a couple of weeks without any major flaws. Made so minor adjustments for power output and I was off to the races.  

Those first few weeks of operating only wetted my appetite to purchase another unit. Just before ordering another kit, I came upon an operator who was selling his 20 meter QCX mini for a fairly inexpensive piece. Lower than a kit, so I purchased the unit.

All was well for a couple of weeks of POTA activations until one day while doing a joint POTA activation with Michael / N4DCW, I noticed a change in receiving on my 20 meter USED QCX Mini. I didn't think much of it until a couple of weeks later when I went to removed my antenna from the unit the center insulator of the BNC connector on the unit pulled out with the coax. 

Again not thinking much of it, I ordered a BNC connector and within a week was back on the air.  During the summer months almost all of my POTA activations are done at or before sunrise due the the hot and humid weather conditions in Louisville, KY. USA, so during those mornings I use on 40 meters. My use of my 20 meter QCX Mini was limited during the summer and fall months of 2023. In late 2023, I noticed the power output of my 20 meter QCX mini seemed to be low.  Checked and found it was putting out less than a watt with 12 volts.  Something had gone array.

Opened up the unit and did a physical exam to check for any obvious issues.

I didn't noticed any signs of improper soldering, so I pulled out the limited test equipment I had to delve further into the issues.  I'll be the first to admit my troubleshooting skills are weak but I was determined to find out why this unit was not performing in its former state.  

Thanks to many internet inquiries and encouragement from others I was bound and determined not to let this little piece of electronics BEAT ME.  With the schematic and voltage readings for components, I checked every component on the board. I found some voltage reading issues but wasn't sure of my findings. I learned many years ago to document my troubleshooting findings. I wrote down all my findings and put the unit back together and set aside. 

The unit sat idle for the rest of 2024 and most of 2025.  As we slowly move away from Solar Cycle 25 max, my Early Bird morning activations have produced GREAT 40 meter DX openings but at times 40 meter band conditions can change rather quickly providing early day openings on 20 meters.  Although I have other multi-band QRP units, I felt it was time to complete troubleshooting 20 meter issues and repair it, to get the Twins (Bada Big and Bada Boom) back together again.

It had been months since I attempted to repair this unit, so I took my time and went back again to double checked voltage readings from months earlier. Still same readings. This helped relieve my anxieties that I was on the right track. The zoom function of my cellphone camera was an huge help in locating potential bad solder points.  

Close up views showed potential solder issues with some of the toroids where enamel had not been fully removed and wires were loosely wound.

My probing of the Q1,Q2,Q3 and Q6 were varied.  The only way for me to be sure of my readings was to remove heat shrink to get a better angle for testing and/or removing transistors.

Now able to get a clean shot of of to test transistor points, I was able to verify that all transistors were shot. Even though my suspicions were on point, I was able to solve my issues, as I continued to be a "Doubting Thomas".  I had to be sure of my readings, so after removing all transistors and testing them; I experienced a certain level of euphoria from troubleshooting my issues and confirming the transistors were bad.

After ordering transistors it was now time for the real work to begin. It is always easier to dismantled something than constructing it. With parts on hand it was time to continue this repair.

I was so thrilled I had solved my transmit and reception problems, I did not take photos of the soldering work to install a Q1, Q2, Q3, and Q6. Nor the removing of enamel from the ends of L1. L2, L3,and L4. It took several times of adjusting the windings on those toriods to boost the power output to 5.5 watts and a few passes of adjusting the band-pass trimmer capacitor, the I-Q amplitude balance of R27 and Audio phase shift adjustments of R17 and R24.  

After work the next day I did a quick POTA activation during unsettled 20 meter HF band conditions and secured 11 CW contacts within 17 minutes from coast to coast from US-7956 Beargrass Creek State Nature Preserve in Louisville, KY. USA.  What I initially thought was an impossible task turned out to be fairly simple. I had repaired my 20 meter QCX Mini.

On Halloween of 2025, I hunted some Parks on the Air activators from my shack during Geomagnetic Storm conditions with Solar Winds over 600, A Index over 30 and K Index of 4.  My thoughts, if I can make contacts during these conditions from my shack where my noise floor generally hangs around S5-7, then my POTA activations will be a piece of cake. 

The following video is a QSO with Dave / WG0Y activating at US-4427 / Apache-Sitgreaves National Forest near Springville, AZ. USA. About 1500 miles from my shack in Louisville, KY. USA.

It is nice to have the Twins back together again. Bada Bing (40 Meter QCX Mini) and Bada Boom (20 meter QCX Mini).