[AMRadio] RE: Yet another receiver update!

[Brett Gazdzinski]

Bacon,
Thanks for the info.
Any idea where I might get the caps?

Its very stable after 15 minutes.
I tried an experiment tonight.
The home brew receiver is mounted in the rack directly above
the r390a.
I figured maybe the heat from the r390a would make the homebrew
drift, but it did not.
While it was on, I compared the two receivers on 80 meters.
Both receivers use the same marantz audio amp, and I can
switch the antenna with one hand, the audio input selector
with the other hand.
At first I thought the antenna connection fell off the r390,
and was checking that.

You may not believe it, but the home brew receiver blows the r390
away.
The r390 has always been my best receiver, but the homebrew
is much quieter, and has better fidelity, especially on the low end.

Perhaps the r390 needs attention, but I never thought so before...

Maybe the somewhat simple homebrew is quieter because its got
less going on inside.
Double tuned input circuit, mixer, LO, 2 stages of 
IF amplification, and the detector (diode tube).

Its not a lack of sensitivity, as I could hear weak stations
quite well, while on the r390, there is a background hiss/noise
level that tends to mask the real weak ones....

If you asked me 6 months ago, I would have said it was
impossible to build something that works so well.
I hoped for something barely usable under clear
conditions, just so I could say I have a home brew station,
but I am ready to retire the r390a as the main receiver.

My original plan was for a regen, but Bruce (NR5Q) took 
too long to get the info in electric radio!

Thanks for the info!
Brett
N2DTS
 
> 
> Hi Brett,
> 
> Hey, you got that thing going... I've never built a receiver up from
> nothing.
> 
> If it drifts down as it warms up, you can compensate with negative
> coefficient caps.  These are the most common type, I think.  N750,
> N1500, N2200, etc; the higher the number, the stronger the effect.
> 
>   Bacon
>