Category Archives: Radios

QCX – low output power

I busted out my QRP Labs QCX 20-meter CW transceiver this evening, just for grins, to see what its output power is–I’m hoping to take it portable this spring. It really is a neat little transceiver… I’ll have to blog about my experience building it at some point, because when I built it last summer (2019), it really was a great time. Here’s a picture of it in the PCB chassis I built for it from QRP Guys plans.

Unfortunately, what I discovered when hooking it up to my 13.8 VDC bench supply, my antenna tuner/power meter and a dummy load, is that the output was less than 1.5 watts! I swapped out the bench supply for a fully-charged 14.8 VDC LiPo battery (so ~16 VDC output), and the power went up to about 1.8 VDC. However, this is still quite a bit less than the ~5 watts that I was expecting! So, I’ll need to do some research. (I will note that this is actually the first time I’ve ever attempted to measure its output power.)

I did open it up, just to take a look at the finals and see if there was any visible damage to the BS170s. Here’s a picture of it opened up (but with the LCD display still in place, so you can’t see the finals).

After removing the LCD display and inspecting the finals with a magnifying glass, I could see no visible damage. So, I’m going to post to the forum, and see what I get. I do see, based on this FAQ, that I might be looking at reworking the output filter a bit.