[Milsurplus] Curiousity...

[Al Klase]

"Kenneth G. Gordon" wrote:
> 
> Can anyone in the group explain why the SRR-11/12/13 and the
> FRR equivalents were never used as much when compared with
> the R389/390 series?
> 

The big difference is architecture.  

The SSR-13, introduced in 1950, was double conversion with
1600/200KHz IF's.  This allowed good selectivity and
reasonable image rejection, but you still have the frequency
accuracy and stability difficulties inherent in a
tunable-first-oscillator design. Add to that, soldered in
sub-minature tubes, some of which were running too hot, and
you're probably going to be interested in a better set.

The R-390, 1951, based on the slightly earlier 51J, uses
triple conversion with a crystal-controlled first local
oscillator.  The second LO only needs to tune a single 1MHz
range, and is, of course, the highly stable Collins
permeably-tuned-oscillator (PTO).

The Collins receivers represent a major shift in
general-coverage receiver design, and were fundamentally
superior to everything that came before in frequency
accuracy and stability.

If you want to find them, use a Collins.  If you want to
listen to them, use a Hammarlund.

73,
Al



-- 
Al Klase - N3FRQ
skywaves@bw.webex.net
Flemington, NJ 08822
Web Page:  http://www.webex.net/~skywaves/home.htm