From: "Bob Bruhns" <[EMAIL PROTECTED]>
After scouring the internet for a while now, I still
can't find any articles at all on the details of the
Taylor circuit.
I found an article by Hoisy from AM Press/Exchange
where he refers to W6QYT and W3PHL, and the Taylor
super-modulated circuit.
I think there may be some confusion here. The Taylor modulation scheme was
sometimes called "super modulation" but it is NOT the same thing as the
upside-down tube circuit that W6QYT and W3PHL are famous for.
The upside-down tube circuit is basically a high level balanced modulator,
adjusted for double-sideband reduced carrier output. W6QYT's original idea
was to reduce the carrier just enough to invert the negative peaks that
normally would have resulted in overmodulation. He wrote an article in QST
sometime in the late 40's entitled "overmodulation without splatter." Later
on, he took this idea several steps forward and became active with early
amateur ssb.
The Taylor circuit operates somewhat similarly to the Doherty high
efficiency linear or Terman-Woodward grid modulation scheme, but without the
quarter-wave phasing lines that make those circuits nearly impractical for
amateur use where the transmitter frequency is not fixed. It works on the
principle that one tube, the "carrier" tube, takes care of the signal from
zero (100% negative peak modulation) until it reaches saturation at full
carrier, and then a second "peak" tube kicks in to deliver the additional
output required to achieve full positive peaks. The Taylor circuit is
supposed to operate at about 60% carrier efficiency, as opposed to the 33%
carrier efficiency of a normal grid modulated amplifier. The original
circuit appeared in an early 50's issue of CQ Magazine. I think Hoisy
played with it some, but I never actually heard him on the air with it.
Don k4kyv
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