PHSNA & Measurement Receiver

Nick Kennedy
 

I've been working on an SSB exciter using my Si5351a programmed as an I/Q VFO and some circuits from EMRFD. I finally got my two boards all wired up. Hooked up an audio generator and my Si5351a I/Q VFO and took a listen on the K3. It sounded awful and I couldn't make heads or tails of the mass of carriers and/or spurs I was hearing. But that often happens when trying to use your receiver to evaluate something on the bench.

I remembered I had this Measurement Receiver thing - inspired by Hayward, I think and designed by W5JH and N5IB and I wrote the code for PHSNA to take and show the data. It can be kind of a poor man's spectrum analyzer and it seems to have enough resolution to separate carrier and sidebands when the modulation signal is 1000 Hz.

When I looked at the data in Excel it still seemed like a mess, but when I looked at the relative amplitudes maybe it's not all that bad. The harmonics of 1000 Hz may come from my audio generator or might come from my circuit but they're not too bad except I don't know why the 3000 Hz one on the USB side is so large.

I haven't tried adjusting my sideband balance control yet, because I'm not sure how to assess the effect in real time.

That Measurement Receiver function in PHSNA hasn't gotten a lot of work due to the small number of users. (Am I the only one?) It doesn't do real time plotting, so I had to take the CSV and plot it in Excel. Not difficult though.

An image of the plot is attached.

73-

Nick, WA5BDU

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