[Elecraft] [K2 4922] IF Amplifier Alignment

[David Woolley]

Clark Macaulay wrote:
> build process was unable to get 3.80: my dmm reads 3.76 but only at the
> extreme end of R1's range.

I forgot to mention that I can only get 3.79, but that seems to be a bug
in the manual.  If one assumes U2b (i.e. got the a and b mixed before)
doesn't load the voltage, I think the end stop voltage with all
components nominal is 3.82; that means that 3.76 is less than 2% out, so
within the component tolerances.  It looks as though the manual should
really have said set R1 at the end stop.

>    
> At first, I didn't think much of it and have started on the Phase II
> of the RF board. Your message would imply that the desired 3.80 is
> probably a minimum and I can't even reach that! Since I've always had

It's a maximum.  The original design didn't have a variable, but it was
found that many people wanted to lower R1 slightly.  The material that
describes the mod to the old version gives a better description of how
one should vary R1; the current manual simply says you may want to
adjust it, without any clue as to why.



-- 
David Woolley
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