Ever since marrying up the IC-2820 with its intended antenna, the newly erected GP-98, I had been wondering about some distortion that was particularly apparent on the audio from the club repeater's idents (both morse and voice). The audio gets distinctly raspy, and although the S meter is pegged fully high, the BUSY indicator flickers when the audio is affected. The worst occasions sound really quite bad, but the situation seems to vary somewhat. This afternoon I noticed a particularly bad phase, and decided I had better investigate.
From a high-level point of view, the problem can only be with the radio or antenna system (including feed line). Luckily, I have a perfectly good radio to act as a comparison - in the form of my IC-7000, which of course does 2m and 70cm. Connecting the, very 'gainy' GP-98 to the IC-7000 I was able to listen to a number of idents from the repeater, and these were all noticeably clean and very nice sounding audio. I also took the trouble to test the antenna SWR on the upper part of the 2m band, and found it satisfyingly very low. That should have been the case, but I had never analysed the GP-98 since installing it, so that's nice to have verified.
My Yaesu VX-8R had also had clean audio on every occasion I had used it with the repeater, though I have no way of currently connecting it to the GP-98, so couldn't achieve a good comparison there.
In any case, it certainly looks like the problem lies with my IC-2820 right now. Perhaps this is a mis-calibration or something in the radio that manifests the poor handling of a strong FM signal and/or its generated audio levels. I shall do some more listening in the next few days, and also sample opinion on the matter.