[R-390] R-390 sensitivity measurements

[DJED1 at aol.com]

I think the test serves two functions- first, you can tell if a particular 
repair to the radio has improved the performance in a relative sense, and you 
can compare two radios in a relative sense.   The test is probably useful in an 
absolute sense only if you define all of the test conditions- then a 
knowledgable person can calculate the differences in measured performance based on the 
setup.   For example, testing at 8 Kc bandwidth versus 4 Kc gives a 
degradation in sensitivity of 3 dB.
I think tweaking the radio for the best sensitivity has lead to its 
reputation as one of the best weak signal receivers ever made.   I've found it to be as 
good as my R4C and distictly better than my SP-600.   But I won't try and 
argue that its got 0.0XX microvolt sensitivity.   Maybe the uncertainties in 
measurement is why the spec numbers are so loose.
Ed