[TMC] GPR90-RXD Receiver & SSB

[rrkrr]

There is no real product detector in the GPR-90, (unless you have a
GSB-1 lying around) so if you want to receive SSB, you have to
compensate the RF gain to optimize the detector response.   It sounds as
though you may need a bit more BFO injection, if you are having to back
off on RF gain that much.

Another item to look at is the slide switches on the rear that are used
to select the external signal connections to the GSB-1.  On the GPR-90 I
had, the internal contacts on these switches were corroded.  I got a
considerable improvement in performance after prying these open and
cleaning the contacts.

Bob
K4ERR

Mark Johnson wrote:
> I recently acquired a GPR90-RXD receiver and did a pretty thorough
> overhaul and alignment. I replaced some weak tubes, a few leaky
> capacitors and as mentioned, I then did a very thorough alignment
> using better than average test gear.
>  
> While the sensitivity is good and the receiver is OK, I find that
> using it for SSB or even CW, it is not as good as other receivers I
> have of similar genre. I have to back the RF gain control off to the
> point where sensitivity suffers or it will overload. I increased the
> value of the coupling capacitor from the BFO circuit and that helped a
> bit but as mentioned, other receivers of similar genre are better even
> though they, like the GPR90-RXD, don't have product detectors.
>  
> From the experience of others, is this common for this receiver?
>  
> Overall I have to say I'm disappointed with the receiver. I've had
> many "Boat Anchor" receivers over the years and always wanted on of
> these TMC receivers. Its no where  close to any of the Collins
> receivers, R390's, 51j series, or even my RCA CR-91a.
>  
> What's the experience of others?
>  
> Mark V Johnson VE3DJU/VE3DDI
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