[Premium-Rx] Racal 6790/GM First Mixer Question

[jmcvein at teleport.com]

Date sent:      	Tue, 27 Jul 2004 19:20:34 -0400
From:           	Edward Knobloch <ed.knobloch at verizon.net>
Copies to:      	premium-rx at ml.skirrow.org
Subject:        	[Premium-Rx] Racal 6790/GM First Mixer Question

> Hello,
> 
> Does anyone have the schematic for the first mixer of the 6790/GM? (It
> is in a sealed tin box on the A-2 card.)  I know that the box contains
> four MOS FET transistors, but I would like to know what's going on. 
> In the tech manual, the schematic for the A-2 card merely shows a
> black box for the mixer, labled U1.
> 
> Thanks,
> Ed Knobloch
> 
> 
I got extremely good info out of the Siliconix low power discretes 
databook, 1989.  App note LPD-14 covers the commutating mixer
design used in the various Racal front ends.  DMOS FET parts 
SD210 Discrete, Si8901 IC, and SD5000I DIP are good parts to 
use, If you can still get them.  Note the need for a square wave
LO drive, Racal gets this by driving the LO amp to 1dBc.

Jim Mc
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