GPIB control of an HP8591 spectrum analyzer

Nothing in any of these manuals?

If not, then they don't like switching that power and some other output is available to control it...maybe through a switched attenuator or something...

Not that I could find. Anyway, the 28V output is specific to the noise figure measurement option, but the associated docs, the "HP85719A Noise Figure Measurement Personality User's Guide" (who invents those silly phrases?) doesn't seem to have it either.

Well, it's switched on and off at a rate of a few tens of cycles per second while running the built-in noise measurement routine. I'm trying to use a noise source that has relays in it, and which cannot keep up with that switching rate.

Maybe you're right: They don't want me to control it directly. I'll find some other way, if I have to.

Thanks, Jeroen Belleman

Did you check this 200 page manual:

It looks like the same option...reading it now.

If there is a workaround, it is not obvious. You're just going to have to get your hands on an HP 346B noise source...

Or hardwire your noise source ON, and then rig up a 28V to logic level controlled PIN diode or GaAs switch inline with its output, that is not hard...the drawback is the personality module stores an ENR profile for the 346B, but this can be manually recalibrated, which you might try with your new noise source.

Here is the technical info for the 346's:

which your SA expects....they are attenuated avalanche diode generators. Looks like they run $1k used.

Thanks for your suggestions and help.

I *have* a 346B, but for this test I was using a noise source based on pair of terminators, one at room temperature and the other at 77K, using LN2.

All this is in a VME-based test setup for low-noise pre-amplifiers. I've ended up using a digital I/O module to control the noise source. Not as elegant as using the dedicated 28V spectrum analyzer output, but it gets the job done.

Thanks again, Jeroen Belleman