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HP 8590A Opt H18 (1.8GHz) Service/schematic? Going 1.5GHz+

Question asked by Peskydan on Nov 26, 2011
Latest reply on Nov 28, 2011 by tabbott
Hi all,
I've checked all the service documents I have for the 8590A, and unfortunately nothing seems to contain information on the H18 option (extended operation to 1.8GHz).

I've looked in

"Support Manual Volume I & II" (08590-90096, Nov 1988, includes opt 001, 021, 022, 023, 030, 040);
"8590A Series Analysers Component-Level Information Packet" (5963-2951, Jul 1997); and
"HP 8590 Series Assembly Level Service Guide" (08590-90316, Apr 2001) to no avail.

There would presumably have been other service documents, addenda, or service notes etc. covering the changes for options like H18, since I believe it was a fairly common option, and it's not really possible to do performance verification (to specification) without the information. Currently I can only guess which assemblies are modified by H18 - presumably the software ROMs and factory cal eeprom data; but possibly also sweep ramp gen and/or YIG module would have needed alteration, as some of the local oscillator frequencies and filter passbands may have been shifted slightly. This is partly what I'm interested in finding out, since an unmodified 8590A without H18 is 'sort of' capable of operation to around 1.8GHz.

For what it's worth, the H18 wasn't available when the 8590A was introduced in '87 but appeared the following year, and was pretty cheap as part of a new unit (around $300 extra I believe). This suggests there's not a lot to it.

So if anyone has any relevant documents, or an idea of who to ask or where to look, please let me know. I will of course also share anything I come up with, if anyone else is interested. :)

Alternatively anyone with an 8590A with H18 and a few minutes of free time, it would be interesting to tune it to 0Hz freq, 0Hz span, and measure the 1st LO output frequency. In a standard 8590A this is offset by 2.05GHz, reaching 3.55GHz when the analyser is tuned to 1500MHz. Such units seem to let you tune the 1st LO well beyond spec; the LO on mine will span 1.9GHz to 4.05GHz, corresponding to a max receive freq of 2GHz. Despite the LO working, something in the receive chain drops out well before 2GHz, although it does go a few hundred MHz beyond 1.5GHz. Performance in that range is questionable; I can't do much testing since my only suitable synth above 1GHz is an 83220A DCS1800 test set, currently in storage. If anyone else is interested though, I'll get it out and see what the 8590A picks up in the 1.7-1.8GHz range.

Thanks for reading.