I did not measure with no sound, as that should be almost 43 db down already (no audio).? At that low of a level you may see things relative to the carrier that leaks through.? I would not expect to see harmonics.? Wonder if the BFO is off so that the crystal filter is not removing the BFO that becomes the "carrier"??
Can you do the test with a dual tone input to the mic?? There is a simple PC 2 tone generator that you can use through the mic to run the test:?
I did a quick test that way before I completed the 2 tone audio circuit from Peter Rachow, DK7IH.
Ran it with a 9v battery.??
Not Pretty, but it works
I also used the "multi tone" setting on my Koolertron signal generator and got the same general results.
To be able to keep the transmitter on, I added a slide switch to the tone board and connected through the 3.5mm plug to the PTT and the tone out to the mic input on the ubitx.? I was careful and monitored the temps on the finals (they did get warm when I had the audio drive too high).
As I stated in the prior email, I used the CW power output reading on my Nissei SWR/Power meter to set the audio drive to get the same power out.? I had adjusted the two tones relative amplitude to each other using the audio spectrum analyzer program that I listed before.? Would like to know the design value for the audio input of the ubitx, would be easy to set that up with a scope.
Net result is that there is a spur issue, though not high enough, nor on a band that I use.? CW harmonics are out of compliance, however there were not above the -43db with the two tone input.? Became just as bad if audio drive was increased to an above CW power level (8.5 watts for me on 40 meters with 13.5 volts to PA only, 12v to rest of rig)
Still learning how to use the tools.? Not exactly as I expected, need to adapt to what is available.? Still think a Siglent or Rigol is in my future shack.
Waiting on the QSX to become available to do comparison testing.
Above are my interpretations of my experiences.? Yours may differ
73
Evan
AC9TU
