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From: whit@milton.u.washington.edu (John Whitmore)
Newsgroups: sci.electronics
Subject: Re: HP Spectrum Analyzer 8558B Part Question
Summary: Matched pair Schottky diodes
Message-ID: <7899@milton.u.washington.edu>
Date: 21 Sep 90 00:43:55 GMT
References: <4574@qip.UUCP>
Organization: University of Washington, Seattle
Lines: 20

In article <4574@qip.UUCP> john@qip.UUCP (John Moore) writes:
>
>I have an HP 8558B Spectrum Analyzer that has a blown first mixer diode.
>Does anybody know which diodes would be suitable replacement. HP gets
>big $$ for a replacement pair.
>
	HP makes a large line of Schottky diodes at all sorts of prices;
matched pair "5082-2306" for $30, "5082-2351" for $50, and "5082-2804"
for $1.31, according to Almac-Stroum's catalog (a few  years old now).
	Unless you know exactly what to get, performance will likely
suffer.  Do these numbers look familiar?  HP dealers can get you the
parts in small quantity at (perhaps) better prices than HP's repair
depot will offer.
	Don't even consider germanium, by the way; the turnon
characteristics of a diffused diode are not nearly as controllable as
those of a Schottky barrier, so matching is far worse.  This causes
some odd effects (like amplifying noise in the LO and shifting it
to the IF frequency...).

	John Whitmore