Hi Andrew,
I think you are right about the RBW. If I come down to a RBW of about 300 Hz it is working. Since this was for testing and quick checking of IP3 of an amplifier, I increased RBW to 5kHz. In this case I can see the two main carriers. With the low RBW they hide behind the limitlines ( picture lowrbw.jpg ).
If I increase the RBW to 3kHz it will pass ( picture rbw3khz.jpg ).
It will fail at a summ level somewhere below -73 dBm.
It gets worse if you increase the span…
Anyhow this was working in Version 3.1.11.
So the algorithm of checking has changed. If it is like your wrote that you are checking single samples against the limit you may run into trouble when you have a good generator. Should you not check against a interpolated line between two samples ?
I really hope you can get it running, because I ever wanted the limit lines stored with the preset as it is first done in this version.
The limits I used:
249.8,-200
249.8995,-200
249.9000,-60
249.9005,-200
250.0995,-200
250.1000,-60
250.1005,-200
250.2000,-200
Best
Volker