[R-390] R-390 sensitivity measurements

[DJED1 at aol.com]

Here's another bit of trivia which I hope will entertain.   In looking at 
Dallas' other postings, he discusses a method of measuring receiver sensitivity.  
 From my view, I'm not sure there is an absolute correct way, but just for 
fun I looked up the MIL spec for the R-390 (MIL-R-13947B) to see what the test 
requirement was.   It's pretty close, but not exactly what Dallas discussed.   
The spec has two tests: AM and CW.   The AM is performed by turning the 
generator modulation on and off, with 30% at 400 cycles modulation.   The signal 
level is set for 10 mw audio out with modulation, and 1 mw with no modulation.   
The only difference from his test is that it is done at 8 Kc bandwidth, and a 
125 ohm matching resistor is in series between the generator and the receiver. 
  You still need to do the correction for the generator reading to get the 
voltage at the receiver.
For the CW case, the setup is the same, except the generator is unmodulated, 
where signal is carrier on and no signal is carrier off (still in the 8 Kc 
bandwidth).    The AM spec is 3.3 uv except in the 16-32 bnd, where it is 4.4 uv. 
  The CW spec is 1 uv.    
This, I believe, was the final spec for the R-390 and was used for acceptance 
testing.   I never did much like the concept of turning the modulation on and 
off, but this gives that approach significant legitimacy.
Ed