[ARC5] TN 1B/APR-1 and TN 2B/APR-1 Military Radio Tuners

[Mike Hanz]

On 6/24/2013 1:09 PM, Robert Eleazer wrote:
> According to an impeccable reference source - the G&G catalog from the mid-70's - the TN-1 covers the same range as the TN-16, 38-95 MHZ, and the TN-2 the same as the TN-17, 74-320 MHZ and both are interchangeable in the APR-4.
>
> The TN-3 is the same as the TN-18, 300-1000 MHZ..  The TN-19 covers 975 to 2200 MHZ. The TN-54 is the one that covers 2200 MHZ to 4000 MHZ if you want that range.
>
> Apparently the APR-1 was virtually the same set but only had tuning units for 38 to 1000 MHZ.

The two had a lot of similarities, but the APR-4 benefited from a 
slightly later start date, resulting in refinements like a switched 
attenuation network that permitted more accurate signal measurement.  
Actually, the APR-1 also had a fourth plug-in tuning unit, the TN-4 and 
later the TN-4B (motorized), that tuned from 1,000-2,200MHz.

That whole progression from the original General Radio P-540 "test" 
receiver (that looked pretty much identical with its aircraft ATR shock 
mount) through the APR-4Y is a study in accelerated technology 
development.  The so-called commercial P-540 was quickly supplanted by 
two military versions (Army and Navy, naturally) that seem to be 
identical except for the nameplates.  I posted a photo of two of the 
early "competing" tuning units at 
http://aafradio.org/countermeasures/APR-1.html - the Navy version having 
a nomenclature that probably caused a bit of confusion when the JAN 
nomenclature naming system came about the following year.

            73,
  - Mike  KC4TOS