[R-390] Mixer mod for 75A4 - possibly adaptable to the R-390?

[Kenneth G. Gordon]

On 9 Mar 2007 at 13:39, Transmaster wrote:

> Oh really, I wonder if this mod' would work on an 51J3 Collins, mmmmm.
> 
> Ken

Probably. 

I will dig out the ER magazine in which that article appears, and forward 
the info on to you. Ray sells all back copies of ER for $3.85 each. I find 
the magazine very useful and enjoyable.

I have posted the schematic for that mod to the Glowbugs website here:

http://www.mines.uidaho.edu/~glowbugs/75A4Pullen.pdf

It may have enough information that you won't need the ER article, 
although that article contains some reliable test information on what 
was discovered about how well it works.

IMHO, it is well worth doing.

BTW, ER also recently printed an article on a mod to the AGC system 
of the R-390A. The result is an almost perfect AGC system with no 
overshoot, and almost instantaneous rise time. It requires no added 
holes and only a few added components. It makes the R-390A an 
extremely good SSB and CW receiver, yet doesn't change its AM 
characteristics.

The system and associated ideas are also applicable to many other 
receivers.

I'll try to dig out that one too.

Ken Gordon W7EKB