Civilian Wartime Radio - Further Notes

[Alistair D]

I can't find it now but I have come across a description of a compression system for AM transmitters which allows greater than 100% modulation! 

The system you describe is called asymmetric modulation. It was discussed over on VRAT a while back.

https://www.radios-tv.co.uk/community/ra...post-23221
 
Basically the -ve going peaks of the audio are clipped/limited so that the transmitter PA does not saturate. A higher mod level can then be applied to the PA.

Two problems occur when doing this:-

Firstly; The audio signal is now distorted so the sound quality will fall.

Secondly; The receiver's AGC is confused into thinking the signal is smaller than it really so it may not turn the gain enough.  

Al