[Premium-Rx] RF testing with the HP8640B

[pat1mca at aol.com]

Greetings List Members,

The now 30+ year old HP8640B has always been a Signal Generator of Choice for Rx Testing but how many now are up to their original phase noise performance ?

Measuring my 1988 HP8640B today I come up with figures at :  5kHz offset  -126.6dBC/Hz,  10kHz offset  -127dBC/Hz and 15kHz offset -140.5dBC/Hz.

Similar measurements on my year 2001 R&S SMG give :           5kHz offset  -136.2dBC/Hz,   10kHz offset  -140.5dBC/Hz  and at 20kHz offset  -141.6dBC/Hz. 

On the HP beast there are some Mains (UK) 50Hz spurs and also lots of internal Fan generated rubbish which is seriously degrading the performance. So I did all the usual stuff, checked as per book and discovered everything in spec, even changed out all the PSU caps to totally eliminate them for bad ESR - but to no effect.

Has anyone measured their 8640B recently ? I could do with some guidance please as to the best procedure to take from this point onwards to make some progress.  

If in doubt - Ask the HP8640 experts !   So I am.

Please reply offline,

Thanks,

Pat G3YFK