[R-390] re: Call for measurements - 100dB carrier reading

[David Wise]

Oh, that.  I am convinced that R537 was the
work of a naive junior engineer, to make a
100-ohm pot look like a 15-ohm pot.  (My position
is weakened, however, by the fact that he used
22 not 18.)  And it does - as long as R523 is
full CW.  I sense a deep wrongness there.

I won't repeat the computations I posted earlier,
but the upshot is that the smallest value R523 ever
needs to be set to is about 4 ohms and the largest,
about 7.  10 is available cheap, but if you could
find a 3 and put it in series with a 3.9 fixed,
it would be as good as you can get.

Regards,
Dave Wise

> -----Original Message-----
> From: r-390-bounces at mailman.qth.net
> [mailto:r-390-bounces at mailman.qth.net]On Behalf Of Barry
> Sent: Wednesday, August 29, 2007 1:01 PM
> To: R-390 at mailman.qth.net
> Subject: RE: [R-390] re: Call for measurements - 100dB carrier reading
> 
> 
> >One person recommended a 20-ohm pot from
> >Surplus Sales of Nebraska.  He feels that 18
> >ohms is the ideal value.  I disagree, 8 is ideal.
> 
> I was going on the fact that the original 100-ohm pot has a 
> 22-ohm resistor in parallel with it resulting in an 18-ohm 
> variable resistance.
> 
> Barry - N4BUQ