[BC] FM History

[rj carpenter]

Oops, full of errors.

> Edwin Armstrong invented a new method of encoding audio onto a
> transmission carrier.

FM had been know for a number of years. It had long been discarded 
because only narrow deviations were used and it didn't work 
satisfactorily with crystal sets and simple tube receivers.  Armstrong 
at least recognized the importance of wide deviation and a LIMITER stage 
in the receiver, which made FM work well.

I won't comment on the Sarnoff Conspiracy.

> Before WWII, there were 50 FM stations on the air.

Not so. The February 1942 issue of Milton Sleeper's FM Magazine said
that there were 29 FM stations on the air with daily schedules. This
included experimental stations, such as Armstrong's. The FCC had issued
a total of 54 CPs and licenses as of February 17, 1942. Some of these
were in experimental, not commercial, operation.

> The ensuing war diverted resources and froze development.

FM was used in Western Electric radios used in WW2 tanks and jeeps. Look 
up the BC-603/604 and 683/684 pairs, introduced in 1942. They were very 
nice radios.

> After the war, David Sarnof and RCA, still out to hold control of
> their radio empire, pressured the FCC to change all of the FM radio
> frequencies from the 50 MHz band to 100 MHz a move they knew would
> instantly obsolete all of the exiting FM radios, and cause Armstrong
> to lose his personal investment in FM radio. Sarnoff claimed that he
> needed the existing FM frequencies for the new television. Even now,
> we do not have a TV channel 1 because it was unsuitable, requiring
> an unobtainable ten percent bandwidth for television. It later
> became the six-meter amateur radio band.

There were relatively few FM broadcast receivers in use before the 
frequency change.  In retrospect, we should be very happy that FM was 
moved. The sporadic-E interference in the old band would have been 
severe. TV Channel 1 was 44 to 50 MHz. The ham 6-m band is 50-54 MHz. 
The pre-WW2 5-m ham band was 56 to 60 MHz.

http://www.tech-notes.tv/History&Trivia/Channel%20One/Channel_1.htm

I'll stop here.

bob