Earlier quoted context omitted.
That doesn't sound right at all. I mostly use mine as a TDR (50 GHz with 83651B) but I can generally reload saved calibrations from months ago, less than 5 minutes after a cold start, and still see I'd go through the receiver channel tests in the manual and try to isolate the problem to the test set or IF box. Does S21 drift as well?
Thanks, it's really useful to have a reference point. Having played about a bit with which device is left to warm up, I'm fairly sure it's the 85102 (IF box) that's drifting. I've also tried my old 8350B sweeper instead of the 8341B and although the pattern's very different (different band-switch points) it drifts about equally badly. The odd bit is that it looks like it's related to the sweep position - I get a sawt…
If you can get your hands on an 8360 source, it will synthesize both the start and end of RAMP sweeps (starting on the second sweep -- it looks to see how far off it was and corrects it), and you will also have significantly faster STEP sweeps.