[Milsurplus] Re: BC-733 an iron radio

[C. Whitaker]

de WB2CPN
You're right, there were two finals on the CAA ILS.
It had a final for the carrier, but tapped off a little of
the RF to feed TWO other finals.  These other finals
were not fed with DC voltage, but fed AC voltage
from large electric motor driven generators.  One
generator feeding one SSB PA the 90 Hz, the other
feeding 150 HZ to the other SSB PA.  These generators
were technically called frequency converters, ( 60 Hz
to 90 Hz, and 60 Hz to 150 Hz).   The SCS-51 and
the MRN-7 & 8 used a "bridge modulator" to generate
each of the two SSB frequencies; 90 and 150.  Each
coaxial bridge had a rotating wheel capacitor that
ballanced/unballanced its bridge. One wheel had three
capacitor arms, the other had 5. They rotated at 30 cps.
They weren't reliable, but they didn't weigh 5000 lbs
like the CAA generators did.  All these systems had
the station ID amplitude modulated on the carrier, and
voice on Localizers was an option.  Also, TRIVIA, but
SSB was in use on Trans-Atlantic telephone circuits well
before WWII.   Also, maybe the reason for the armor
plate on the 733, it enhanced the frequency stability
of the receiver, what with it being on thin ice as it was.
73  Clete