[TMC] GPR-90RXD stuff

[Les Locklear]

I've been reading the TMC thread with interest.

Having owned both a GPR-90 s/n 1120 and GPR-90RX s/n 7514 I have come to the conclusion that the GPR-90 series is one of the most visually appealing
general coverage receivers built. 

Dial readout is quite good, stability good enough for that period. My only complaint is the if filters. They are barn-door wide
and very poor for any kind of critical listening. 

The GPR-90RX was much better on sideband than the GPR-90.

Both were sold/traded years ago and I never missed them.

Les Locklear

----- Original Message -----
From: Richard Knoppow <1oldlens1 at ix.netcom.com>
To: <tmc at mailman.qth.net>
Sent: 8/14/2021 2:53:45 AM
Subject: Re: [TMC] GPR-90RXD stuff
________________________________________________________________________________

   Some more GPR-90 questions.  Because of the previous thread I 
began to read over the various GPR-90 manuals at the TMC site. In 
particular I wanted to know what differences there were between 
the 90 and the 90RXD. I discovered a surprise to me that the RXD 
had a built in product detector. Its activated by the SSB switch 
on the back apron. It has a 6BE6 which operates either as a BFO 
supplying the diode detector or as a product detector taking a 
signal from the IF and connecting to the AF amp. There does not 
seem to be any provision for a  slow release AVC. This is a 
puzzle to me since the receiver is set up to work with an 
external SSB adaptor like the MSR-6 and could work with a more 
comprehensive one like the MSR-9 which has means for connecting 
to a receiver's AVC. So, what was the purpose for this detector? 
Without a slow release AVC it can't have been too satisfactory. 
In addition the IF bandwidth is a little wide for SSB. What was 
going on there?  The receiver has other changes, such as a double 
RF amplifier and perhaps some others. Its a very frustrating 
design to analyze without any idea of the intended market.

-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL

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