Let me try my hand at this...

"crb" wrote in message ...
Still not sure what it is.

I know I do a test at work where I put in a 3 KHz deviated, 1 KHz tone
into the FM receiver port while probing an audio point going to the
SINAD port on the test equipment.
Increasing the input level makes for a larger SINAD value (which makes
sense) Looking for at least 12 dB SINAD.
What is so special about 12?

Can't get my mind around it. Is the test tone 12 dB stronger than noise
+ distortion?


That's the simplest way to look at it. The desired signal (tone) is
(approximately) 12 dB above the junk.


Is the the input value in dBm on the test equipment the sensitivity of
the receiver at 12 dB SINAD.

Yep. That's it! The INPUT level, which gives this special output
condition, IS the sensitivity.


When measuring sensitivity, you need some kind of a reference point and the
signal to noise ratio at the receiver output (after a fashion) is what is
used here. . If I recall correctly, way back, AM receiver sensitivity was
the input signal (with some standard modulation) which produced the rater
power output (audio) with the volume cranked all the way up.