[R-390] More C709 info

[Tim Shoppa]

Flowertime01 at wmconnect.com wrote:
> Why are you still trying to peak a VFO in the middle of its frequency range, 
> when you know you want a flat output across the range?

I believe that Barry's Q calculation was not correct: my scribblings
put the Q at closer to 1.

This is extremely consistent with my observation that VFO output is
highest near the center and falls off by 20-30% towards the edges.

> Why do you want more mixer noise at 500KC in every band than you want at say 
> 100KC and 900KC?

If he has too low of a injection level, then mixer conversion
drops like a rock. Above a certain level, you are mostly insensitive
to variations in injection (although you are right, mixer noise does
go up.)

My guesstimate is that a "good place" is more than 6V pk-to-pk for
the 390A mixers. Last I heard he was struggling with a measly volt or
two pk-to-pk, and at that low level conversion efficiency in the mixer
is gonna be pretty rotten.

> What part of flat like a pancake are you missing?

Who wins in rock-scissors-pancake?

Tim.