I finally sat down to do some more work on my uBitx -- with the external relay daughterboard
-- wired with just regular, unshielded wire. I recall that I damaged and lost one section of one of the low pass filters (I think on 20 meters).
Here attached is the first plot I got attempting to look at the CW harmonics on 80/40/30 meters, using a 12V supply. I had 67 dB of pads in line with the Siglent spectrum analyzer, and that entered as a correction factor. Video and RBW were 30 kHz.
Frequencies are from 3-63 MHz so each major division is 6 MHz. using "traces" with an averaging of 2, I was able to capture and hold traces of 80, 40 and 30 meter CW signals. You can figure them out from the frequencies, but
80 meters = purple
40 meters = yellow
30 meters = blue
The blue horizontal line is my attempt to mark the FCC limit requirement for harmonics, 43 dB below an observed output of about 37 dBm.
If I should make this measurement differently, I'm quite willing to hear improvements! This was my first crack at it, and I've only had the spectrum analyzer for 2 months. It has been used on MANY projects already.
I believe you can see that the harmonics are WELL below the limit for these items tested.
I'll work at this some more and hopefully made more and better measurements.