[Milsurplus] history and evolution of the Collins gear

[Meir WF2U]

Interesting that the first model of the Russian R-250 series receivers was
manufactured in 1949 as well - it's also using the calibrated variable first
IF with the crystal converter in front of it, a la Collins. The difference
is that while in the Collins the IF tunes a 1 MHz range, the R-250(*) tunes
a 2 MHz range (1.5 to 3.5 MHz). The 215 kHz fixed second IF has a
continuously variable bandwidth from 1 kHz to 14 kHz (same principle as in
the Hammarlund SuperPro receiver). For additional selectivity options, audio
frequency filtering with selectable bandwidths of 8, 5, 2.5 and 0.3 kHz is
built in. The BFO has a calibrated tuning dial in the range of +/- 5 kHz
from center frequency. There is a crystal calibrator, a delayed, amplified
AGC which works on CW, and a separate detector for CW. 
My experience with the R-250M version, manufactured in the mid-1950's is
that it works great on SSB as well and the AGC is fully functional and no
lack of BFO injection is observed. The R-250M uses the standard metal octal
tubes (all have US equivalents), running at 160 VDC plate voltage. (The WW2
US Navy RAX receivers used 160 VDC). This keeps the receiver cool, and the
tube life long. Incidentally, the receiver has a built-in tube checker which
reads the emission of each tube as selected, in operation. As long as the
needle is within a certain indicated range, the tube is operating normally. 
The receiver is somewhat larger than the R-390 series, and heavier. The
power supply is a separate unit.

The R-250(*) were highly secret, were used for intercept work by the USSR
government agencies, the military and the Soviet Navy.

I have to say that this receiver is the best octal tubed receiver I ever
used!

I wonder whether the Russians came up with the idea of crystal converter
front end independently, or maybe they had a trickle of information from the
Collins design team.  

73, Meir WF2U
Landrum, SC













































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-----Original Message-----
From: milsurplus-bounces at mailman.qth.net
[mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of Al Klase
Sent: Monday, May 28, 2012 11:10 AM
To: milsurplus at mailman.qth.net
Subject: Re: [Milsurplus] history and evolution of the Collins gear

Folks,

The post-war Collins receivers were a radical departure from almost 
everything that came before in that you could set the dial to a desired 
frequency, and be certain you were within a kilohertz or two.

"If you want to find them use a Collins.  If you want to listen to them 
us a Hammarlund." :-)

The basic architecture is a crystal controlled converter in front of a 
carefully calibrated tuned IF.  The IF tunes a 1 MHz range, and the 
crystal converter has 30 positions.  A fairly complicated mechanical 
arrangement of gears and cams keeps the front end, crystal 1st 
conversion oscillator, and tuned IF in sync.

The first radio in the family was the 75A in 1946.  This was 
ham-bands-only, and is mechanically a lot simpler than its successor, 
the general-coverage 51J1 in 1949.  The R-390 appears in 1950, and is a 
much more expensive elaboration on the basic theme.  These were the 
descendants of the WWII AN/ARR-15 that pioneered many of the basic 
techniques.

Al

On 5/28/2012 3:56 AM, Raymond Cote wrote:
> The mil list has been talkin lately about the R388 and 51J3 equipment.
This brings to mind the thought of the evolution of these great receivers.
When was the first designe, what was the first one?  51j1???   Was there
units before the J series?  What are the capabilities of the various
lineage?  from the 51H, 51J, 51S R388, R389, R390 390A 391 and so forth?
Does anyone have all this in writing or does it have to be compiled, perhaps
on these lists?
>
> thanks all 		 	   		
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-- 
Al Klase - N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/

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