Mallory tech book on TV in 1942

[Steve McVoy]

I'd like to hear the full story of the decision to go with FM sound. The selection of FM meant that good audio could be received at signal levels way below what was needed for good video. AM sound would have resulted in sound and picture requiring about the same signal levels for acceptable performance. So, in a way, FM sound didn't really have any advantages over AM in television.

The reason wasn't intercarrier IF, since it didn't exist in 1941. And FM detectors were more complex than AM ones at the time.

Anyone know the full story why FM was chosen?

[wa2ise]

Originally Posted by Steve McVoy

... The selection of FM meant that good audio could be received at signal levels way below what was needed for good video. AM sound would have resulted in sound and picture requiring about the same signal levels for acceptable performance.
... And FM detectors were more complex than AM ones at the time.

That would mean that less transmit power would be needed for the FM sound, to get the same area coverage for it as the video signal would have. Thus less interference to the next higher channel in the next market area. Thus the FCC deciding it was a better choice. The fact that FM would require a little bit more circuitry wasn't that big a deal, as the video part required a large amount of circuitry anyway.