[Premium-Rx] Improvements to the RA6790 / RA1792

[Carcia, Francis A HS]

    Hi all,
There is a high dynamic range second mixer for the 6790 on epay. I'm not
sure if there is any agc action in the module. I added a PAS3 to my 6830
DF second mixer module to make it usable. It also needs the linear to log
converter op amp circuit to get the s meter to function properly.   fc

-----Original Message-----
From: Dan Rae [mailto:danrae at verizon.net]
Sent: Friday, February 18, 2005 6:34 PM
To: Michael O'Beirne; premium
Subject: Re: [Premium-Rx] Improvements to the RA6790 / RA1792




Michael O'Beirne wrote:


  Everyone seems to have forgotten that there is small ceramic filter at
455kHz immediately after the MC1496 second mixer.  


That's only in the RA1792. The 6790/GM front end is pretty different, two
crystal roofing filters in the GM v. the single one in the 92.  RF amp in
the 92, none in the /GM etc.,  Interestingly though, the gain from antenna
to IF input should be identical in both even without the RF stage in the GM


In one of my 1792s I have an approx 8 kHz wide ceramic filter in the 2nd
mixer board and another instead of a link in the FL7 (the wide, nominally 16
kHz, filter) position.  I've also done this (the FL7) in one RA6790/GM, it
gives a useful wider bandwidth for AM etc., as opposed to the ridiculously
wide "standard" 16 or 20  kHz filter.  This is pretty easy to do.  BITE
takes care of the new B/W in the GM, in the 1792 you need to edit the eprom
data if you want the bandwidth display to be correct.

73 
Dan.
ac6ao / g3ncr


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