[TMC] GPR-90 Redesign

[Dave McDonald]

Richard,

If you compare stage by stage, you will find other subtle changes.  These 
were probably needed to control by external oscillators and crystals.  The 
RF input change may have been required to satisfy the requirements of the 
intended market which was government total HF coverage and not the amateur 
market.

My GPR-90 stays on daily on the 22, 19 and 17 meter bands and I have never 
seen any problems with the GG input.

73,

Dave McDonald
Clearwater, FL
K4EWC


----- Original Message ----- 
From: "Richard Knoppow" <1oldlens1 at ix.netcom.com>
To: <TMC at mailman.qth.net>
Sent: Saturday, August 25, 2012 1:37 PM
Subject: [TMC] GPR-90 Redesign


>      I discovered from looking at the schematics that the
> RF stages of the GPR-90 were redesigned for the GPR-90RX.
> The original receiver has one stage of grounded-grid
> amplification coupled to a conventional pentode. The
> grounded grid stage is bypassed for the broadcast band.  The
> RX model has two conventional pentode stages on all bands.
> The tube chosen for the first RF is one that has good IMD
> performance and is pretty quiet. I wonder why the GG stage
> was eliminated.
>
>
> --
> Richard Knoppow
> Los Angeles
> WB6KBL
> dickburk at ix.netcom.com
>
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