[Premium-Rx] mixer fets

[richardreich at aol.com]

Hello Steve,
I know a number of the development engineers who worked on the mixer FETS for both 1772 and 1792 at Racal, and have the benefit of some of their knowledge (and test jigs after the company closed). The type and match of the part was quite a headache back in the 'early' days, and more than 40% if the chosen type did not make the grade in pre-test.
Today, there are a number of far superior FETs to use in respect of all parameters, but it would involve some experimentation on your part. They need to be fast switching types, and well matched - but modern manufacturing techniques make this easier if parts from the same batch are used.
I used some surface mount devices on a copper-clad PCB a couple of years ago - but can't remember the type at the time of writing. They were readily available from Farnell, cheap, and worked very well. There is no magic in the Racal parts.  - just carefully set-up electronics - as it should be. 
Incidentally, I used the same FETs in a Drake receiver - and it was transformed.

Regards.... Richard

Sent from my BlackBerry® wireless device

-----Original Message-----
From: engineroom <steve at engineroom.free-online.co.uk>
Sender: premium-rx-bounces at mailman.qth.net
Date: Sun, 06 Jan 2013 09:52:11 
To: <premium-rx at mailman.qth.net>
Subject: [Premium-Rx] mixer fets

Hi Folks,I need to change mixer fets on a Racal RA1792 it has bsv81 type 
on the circuit drawing but i noticed some posts on here before 
mentioning the sd215de's being used the receiver picks up only strongish 
broadcasts stations but passes bite ok i suspect the mixer, it's the 
later 85830 radio with score.I was wondering if there is a superior fet 
replacement or should i stick with the drawing type?
Regards
Steve in Rugby England
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