This sounds like a good project to share with readers of this group or a
magazine article for QST or CQ. I've always thought a solid state AM
transmitter makes a lot of sense. What keeps me from experimenting with AM
are the tubes and large transformers. How about it?
73, Winston K4CWQ
----- Original Message -----
From: <ToddRoberts2001@aol.com>
To: <jtml@lanl.gov>; <amps@contesting.com>
Sent: Friday, July 13, 2001 17:47 PM
Subject: Re: [AMPS] Why build high level AM?
>
> Several years ago I built a 200 watt all-solid-state Pulse Duration
> Modulation (PDM) AM transmitter using a pair of $5 switching Mosfets in
the
> final Class-E amplifier and one in the class-S modulator. PDM dispenses
with
> the need for a modulation transformer which is the main bottleneck in a
> high-level plate modulated Class-C tube-type AM transmitter. Measured
> frequency response with the PDM rig was ruler flat between 50Hz-12KHZ and
> distortion measured less than 1% at 100% positive peak modulation. PDM is
a
> form of high-level series-modulation with efficiency for both the final
> amplifier and modulator running over 90%. It is amazing to see the final
> amplifier operating at 200 watts carrier output with the heatsink barely
> warm. I run the final amp and modulator from a relatively safe 100VDC
> regulated power supply. If there is a short or some kind of accident the
> power supply simply shuts down. No danger of ozone here! The rig has been
> operating reliably for over 5 years now. 73 Todd Roberts WD4NGG .
>
> --
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>
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