[BC] Supermodulation

[Dave Hultsman]

In a message dated 5/11/05 12:01:32 A.M. Central Daylight Time, 
broadcast-request at radiolists.net writes:
In the late 60's Gates made a "special" version of the BC-5P2
with the 10 kW modulator section of a BC-10P in it. Anyone want
to guess why? <ggg>

Phil Alexander, CSRE

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My guess was it was the only way to do the "Super Modulation" people 
wanted.  They installed a separate power supply for the 
modulator...  Collins also had a "Hot Rod Kit" 125% modulation transformer 
for their 820-E/F  5-10kW. Models.  The Bauer of the day with its 12 Phase 
Power supply had overated its power and modulation transformers and would 
usually get well over 100%. RCA's after the BC5H  were the pits on positive 
modulation until the 5L.
THe FCC imposed the limits of 125% probably because some manufacturers 
began advertising 150% positive modulation.  In some receivers the audible 
distortion increased with heavy positive modulation.

Many of the older plate modulated rigs of that period would not take the 
heavy modulation. I had and old Western Electric 5 Kw. that we had a tube 
type negative peak clipper using a 6H6 and it  did well at the pin on 
positives on both the old G,R. Mod monitor and the "O" Scope.  No 
modulation transformer involved in the transmitter.  One of my buddies 
installed a new limiter on his Class B plated modulated rig and blew his 
modulation transformer twice finally got and oil filled version that would 
take the peaks.

Dave