[R-390] The R390/R390A front end, anything similar?

[Kenneth G. Gordon]

Jack Sullivan wrote:

> Does anyone know if any other receiver has ever been
> built, that had such a profound front end, with 2 or
> even 3 R.F. stages, three I.F. frequencies, two of
> them variably tuned, that helps give profound
> performance. 

BC-779 and its cousins all had 2 RF amp stages and at least 3 IF amp 
stages: Also National HRO-50-1. "If you want to hear them, get a 
National: if you want to know where they are, get a Collins." or another 
variation at the time was, "If you want a RECEIVER, get a National: if 
you want a frequency meter, get a Collins.".

I added a triode product detector to a BC-779 once. It was the quietest, 
most sensitive receiver I had ever used up to that time. In its original 
condition, it was spec-ed at 1 microvolt or less sensitivity. In addition to 
having a wide-range crystal filter of good design, it also had a 
mechanically variable IF coupling system.

In any case, it isn't the 2 (or more ) RF amp stages, and the 3 (or more) 
IF stages that makes a receiver: it is far more than that. Gain 
distribution is one factor. Besides, the older receivers had 2 RF amp 
stages mainly to improve the image response at frequencies above 20 
Mhz.

The three IF FREQUENCIES of the R-390 series had to be very 
carefully thought out to prevent weird mixer products.

Ken Gordon W7EKB