Dear Ed,
You are entirely correct about 200% modulation in AM
commercial rigs. This was in the day when modulation reactors
were driven by a push-pull set of hefty tubes.
With the right iron you could modulate a pair of 4-1000A's
with a pair of 4-1000A's and the sky was the limit.
But this is why the conscientious broadcasters put a compressor/limiter
in the audio chain and kept the studio technicians hands off them, because
this is what would save the licensee's bacon if Mr. Plummer or associates
would visit the station and record meter settings.
My friend Dale Gagnon, KW1I, up in NH, rebuilds commercial and
military AM transmitter chains for low band AM. He has to be very careful
about splatter when keying these huge rigs, and keeps a very close watch
on the output waveform when the mike is open.
As to reverb, it was allowed as an audio "effect", but I never saw
a commercial BC chain with one just operating in the normal
daily broadcast. One of my professors at college worked for Mercury Studios
and he had photos of the reverb and echo setups using the elevator shafts.
Hal
W4HBM
[snip]
Gates developed a BC-5HA which essentialy had a 10 kw RF stage, set to 5 kw
and a 10 kw modulator fed with a separate power supply. As I recall one
station was able to achive close to 200% positive modulation. Of course the
negative peaks were compressed, clipped and otherwise processed.
At that point the FCC decided to establish a rule of +125% positive
modulation peaks. This was so as many stations trying to emulate this
overdrove the transmitter with resulting splatter and interference.
[snip]
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