Re: uBitxV6 SSB transmit has RF out with no audio input, voice distorted when present
|
Almost EVERY piece of current?digital technique freebie software includes a spectrum display.? ?JS8, WSJT-X,, FLDGI are very common ones that all have a spectrum display.
If your BFO is in the middle of the filter....you will have a RESTRICTED frequency range of white noise coming from the antenna.? ?It will be like 0-1500 Hz for example. If you get your BFO?just to one side (where it should be) then your white?noise will expand to 2500-3000 Hz wide.?? That is another clue.
If upper sideband signals (think 20meter voice) work o the UPPERsideband setting, then you areon the correct side of the filter. If they are BACKWARDS, then you are on the wrong side, just change to the other side by changing the frequency of the BFO up or down about 2.5 KHz.
Loads of experimental learning available from this effort.? ?Exactly the same as what my chemistry students will be doing in just a few hours
Gordon
On Mon, Nov 6, 2023 at 3:12?AM Evan Hand < elhandjr@...> wrote: On Sun, Nov 5, 2023 at 07:43 PM, DaveW, KL7HJF wrote:
Gordon,
Your explanation does describe what I am seeing.
Are you familiar with the KD8CEC "IF Shift" function? Perhaps there is a way that might be used as a tool for determining whether the BFO is adjusted to the edge of the filter?
Dave,
I am familiar with the KD8CEC IF Shift function (though, as with Gordon, it has been a couple of years).? It will not help in this case.? The relationship is between the SSB crystal filter and the BFO.? That does not change with the IF shift function in the KD8CEC software.? The shift function adjusts the relationship between the BFO and the IF frequency.
The best way that I found to measure the filter reduction is with a spectrum analyzer and a tone generator.? The one that I used at the time was an SDRPlay RSP1A and the spectrum analyzer software on the SDRPlay website.? Like you, I had an Antuino and tried that.? The issue is the minimum resolution is about 3kHz.? It's too wide to see the difference between the tone and the carrier.? That was true for the other low-cost analyzers that I could find.? The TinySA became available, but it is also limited.? The newer TinySA Ultra can go down to 200Hz resolution bandwidth (RBW), BUT it takes over 8 seconds for a scan.? That could work if you are patient and have a good, constant tone.? It would be a test, adjust, and test again with as much as 20 to 30 seconds between adjustments.
If I needed to do the analysis again, I would return to the RSP1A, as it could go down to 10HZ RBW with a good update time.? It has other weaknesses that keep it from becoming my go-to analyzer.? The ideal is either a Siglent or Rigol analyzer.? Maybe this year, I will break down and buy one of them.
Without the spectrum analyzer function, the method Gordon suggests is the only one I can think of.
Have fun experimenting and learning!
73
Evan
AC9TU
|
