[Heathkit] AT-1 on AM???

Wed, 21 May 2003 23:37:41 -0400

I didn't have an AT-1, but I used a cathode modulator with my Globe
Chief 90 back in the 50's.  Worked fine for talking to all the mobiles
on 75M after school.

It used a 6SL7 and a 6Y6G.  "The Simplest Modulator" was in QST,
September 1953.  Best thing was it needed no HV power supply.  Just
apply filament voltage and plug it into the (cathode keyed) key jack.
Worked great, and gave decent modulation up to about 80%.  I used it
for a year or so, then went back to CW!

There is another modulator specifically for the AT-1 in CQ Magazine
for November 1955.  "A Modulator for the Novice Transmitter".  This
one uses a Heising circuit to plate modulate the AT-1.  It has a
transformer and flashlight battery for a carbon mike as written.
Tubes are a 6C4 and 6L6G.  The article says that "The Heath Company
advises that the [AT-1] supply will deliver safely a maximum of 25 to
30 mA additional current.  If the final amplifier plate current is not
more than 50 mA, this limitation is not exceeded."  "Do not operate a
VFO and the modulator from the AT-1 power supply simultaneously."

73, Garey - K4OAH
Atlanta

----- Original Message ----- 
From: <[email protected]>

> It has been done.  I recall talking to a ham who was using a
modulated
> AT-1 back in the 50s.  I don't recall whether he was using plate or
> screen modulation.
>
> I was using cathode modulation on a 6L6 final.
>
> KoDCF/Tony
>
> Quoting kwylow zinjanthropus <[email protected]>:
>
> > Hello:
> > Has anyone built or used a modulator (plate/screen/otherwise) for
the
> > AT-1? Been thinking about it and trying it out for bragging
rights.
> >
> >
> > Cal, N6KYR
> >
> >
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