Rigol RSA3030 (RSA5065) Strange Behaviour at starting frequencies below 7.5MHz

[AndrewJCS]

I have today observed a really weird behavior in my Rigol RSA analyzer.

For frequencies starting from 7.5MHz or lower, there is a sudden 5dB drop in the noise floor at EXACTLY 12.50MHz. The measured signal drops by half that or 2.5dB.

This is independent of detector type (but significantly more noticeable on average or positive peak detectors). It is also independent of amplitude settings.

It is driving me insane, and I wonder if any RSA owners out there could help me trying the same thing. Suggestion for setup is 100ms sweep, frequency span from 5MHz to 20mHz and auto RBW.

This is an "upgraded" unit to 6.5GHz (so a 5065) and I wonder if that is part of the problem.

Check pictures for details.

Thanks!

[KeBeNe]

Hello,

this looks very much like a faulty flatness calibration