Most people seemed to agree - including stalwart "radio men" Nick (VA7NRM), John (VA7JW) and Adam (VA7OJ) that it sounded like a front end problem in the radio. There have been several comments online about the radio having poor intermod rejection characteristics, and it was supposed by those present that this could bode badly for the overall design and perhaps has a bearing on the observed characteristics of the radio.
Over the next few days I'll hopefully get to learn more about the problem via:
- Adam's radio lab - with an RF generator and analysis gear. I'm taking the radio over tomorrow for a shake-down.
- The club's antenna and bandpass filter set-up. We'll try to discern if the problem is intermod. Should be able to see this on Saturday at the club radio room.
Hopefully these will shine a more scientific light on the nature of the problem and then we can hypothesise over whether the problem is likely a design flaw, or something specific to my particular radio - or indeed the unlikely scenario of user error -perhaps a "don't distort strong signals" setting that I've neglected to turn on :-)