[R-390] Need Resistor info

[James A. (Andy) Moorer]

None of the resistors in the circuit would any effect on the noise of the RF 
stage (except in the extreme, of course - that is, extremely broken). The 
only resistor that would have a chance of having any effect is the grid-leak 
resistor. This is in parallel with the antenna (through a tank circuit 
transformer). The antenna impedance is going to be so low that it will swamp 
(short out) any noise voltage from the grid-leak resistor.

I'm not sure the input noise in an R-390A could possibly be any lower. 
People routinely get sensitivities in the fractions of microvolts. See my 
"noise and sensitivity page" http://www.jamminpower.com/main/noise.jsp. With 
an antenna impedance of, say, 100 ohms, there is a thermal noise of .04 
microvolts on the grid regardless of what resistors are used. Not much you 
can do to reduce that except maybe sink the front end in liquid nitrogen.

James A. (Andy) Moorer
www.jamminpower.com

----- Original Message ----- 
>
> There are many opinions about what resistors contribute what to the sound 
> of high fi amps and other devices. I can't even repeat in general what 
> those opinions are.  I do wonder if a very few low noise resistors in the 
> front end of an R-390A or other receiver might reduce it's self noise just 
> a bit.
>