[AMRadio] W4CJL's Taylor Super Modulation


Donald Chester k4kyv at hotmail.com
Sat Feb 25 17:30:06 EST 2006


>From: "Bob Bruhns" <bbruhns at erols.com>
>
>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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