@abcd567, It was probably the demise of your noise source that alerted me to the issue in the first place, so thanks! (if thats any conciliation )
The noise source and directional coupler does the SWR ok, for what I need anyway. Measuring an open feed line gives you infinate’ish SWR then a good 50ohm dummy load gives ~1:1, the rest can be converted from the db scale between these points. Its probably as good a number as any uncalibrated non professional gear is going to give.
I think I mentioned this previously and I know you are quite familiar with the effects of standing waves. But I’ll rant on anyway. The main thing I found in getting useful results that isn’t mentioned in all the YouTube videos etc, is keeping the feed-lines as short (preferably non existent) as possible. It’s hard enough coming to grips with the results when not having to get your head around the effects of the standing waves and differences that small changes in feed-line length can have on results.
To get the best out of a tracking signal gen or a noise source, I think its important to see the results warts and all on a spectrum display rather than just a number on a meter that often where where feed-lines are involved, means nothing.