Jack,
FYI (not to rub salt into a wound), I set up the recommended scan and ran scans between 3.5 and 4.0 MHz in 100kHz increments to see if any cropped up for my factory-built V3.? All of the scans were clean, exceeding -50DBc.? The spurs were buried in the noise floor if they were there.? This suggests there is an issue with your board.
Is there anything different for your V3 than stock?? ?Is this an actual V3 board or a converted V2?
Gordon,
Does your V2 have any spurs on 80 meters?
All,
I suspect that the carrier is getting through and mixing with the LO to produce the spurs.? That could be a 40 MHz filter issue or a BFO setting.? ? Another possibility is the BFO mixer is not attenuating the BFO on the output.? You would need a high-impedance probe for the TinySA Ulra to measure the signals on the output of the mixer.? The Siglent may have that as an option for the probe inputs.
I have not thought through the impact of changing the BFO.
The above is more brainstorming.? I am open to any suggestions.
73
Evan
AC9TU
