Re: LF: Droitwich Carrier

[RaySoifer@cs.com]

Hi,

I have no AM broadcast experience, having only been chief engineer of an FM (but not AM) BC station in the 1960s, but from my amateur experience, any form of controlled-carrier transmission I've ever seen reduced the carrier when the audio was at low level, not when it was high.  This "downward modulation" that has been measured by several observers would almost certainly imply a degree of overmodulation on audio peaks.  That could result from a number of causes: insufficient grid drive on the RF stages, too much audio relative to the carrier, or if compression is being used, an incorrect setting of the maximum audio level.

I was in England last week, and Droitwich sounded fine on my LF BC receiver, but that doesn't prove anything re overmodulation.

73,

Ray, W2RS