[ARC5] interesting ?

[Michael Hanz]

On 2/23/2018 11:10 PM, Tim wrote:
> Hi Mike - Interesting stuff....I have an APR-4 with several tuning 
> units.  It operates on either 115V 400 or 60 cps AC power (plus 28VDC 
> for the motor I think) , 60 cps is something I always wondered about.  
> For an airborne set anyway.
> Perhaps that was a holdover from the GR Lab instrument design?  Or 
> maybe for shipboard ESM work?

The original GR P-540 had a power transformer that worked on 60Hz - it 
was a test instrument.  The derived aircraft variations (SCR-587, ARC, 
and ARC-1) used a 28 volt DC supply, with an internal 250volt DC output 
dynamotor.  By the time the APR-1 and APR-4 rolled around in 1944, they 
had changed the specification to 10 watts of 28vdc (tuning motor) and 
110 watts of 115vac from 60-1000Hz.  They also included an 80vac tap for 
our UK brethren, reflecting the combined nature of warfare during the 
period.  That did allow those receivers' use on a wide variety of 
platforms.  When the ALR-5 (that included the R-444/APR-4Y mainframe) 
was procured, the contract specified a 380Hz lower limit (upper limit 
1000Hz), befitting its dedication to aircraft platforms.  It also 
dropped the wartime 80 volt tap in the power transformer.

           73,
  - Mike  KC4TOS