John,
That was the W1FB, Doug Demaw preamp from QST, Aug. 1988. I too built one
and discovered there is an error in the ratio of T2. The impedance ratio
should be 112:1 to match the output of the MC1350 to 50 ohms not 10:1 as
shown in the schematic. I ended up with 31 turns on the primary and 3 turns
on the secondary of the FT-50-43 core to get the match about right. I don't
know how that mistake got through.
And yes, it has way too much gain but is still usable by keeping the gain
pot down.
73 Hardy N7RT
At 09:15 AM 6/18/06 -0500, W0UN -- John Brosnahan wrote:
>I ran across an old preamp in my junk box and I am trying to
>find the source of the design, so I can modify it for AM BC DX.
>
>It has an MPF102 JFET first stage and an MC1350 8-pin DIP
>IF amp chip second stage.
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