TCXO woodpecker/no BPF peak #qcx #solution

Daniel Solano Gómez

Hello, all,

I was finally able to resolve the woodpecker on my QCX+40 this afternoon. I thought I would share what I discovered here, in case it'd help someone else out.

The main symptom I was seeing was the infamous woodpecker noise, this time at around 100Hz. While I was poking around with my multimeter measuring some voltages during the week, I had noticed that going into the BPF alignment mode was reading super low, in the range of 0–2, instead of about 8. This afternoon, I set up my oscilloscope and looked at IC3 pin 8. Instead of the 7.02MHz square wave I was expecting, I saw a 10MHz square wave. I double-checked that the reference/oscillator frequencies were set correctly. So, on a hunch/whim I decided to look at the outputs of each oscillator. The 20MHz crystal was fine, as was the output of the 25MHz TCXO. However, while probing the TCXO, the woodpecker disappeared.

In the end, it seems like my connection from the main board to the TCXO had a cold/bad joint. Reflowing and applying some extra solder solved my problem. Now, I have a working QCX+40!


Daniel, AG5UT

Brian N7BKV

Wow, sounds familiar.  I have built three amps and three QCX radios.  I take great personal pride in how I build them.  Worked through any problems and got them all running fine.  Except the last kit, a 50W Amp.  Tried like crazy to sort it out.  No joy.  Went through the NA5Y trouble shooting video.  Got stumped at a failure point.  Turns out that was a defective trace.  But still after that it did not work.

Turns out the final problem was one I caused.  A bad solder flow on the input pad to T7.  Looked OK, but did not figure this out until I watched the NA5Yconstruction series, which has some continuity tests no included in the trouble shooting video.  Sure enough, I was able to isolate the exact problem child.  Reflowed the solder and cooked off the enamel completely and now all is happy!


Glad you are on the air!

Brian N