[heathkit-yahoo] Heath HW-100 Plate Modulation Mod

[Gordon Gwillim]

I would have to concur with Pete on this one.  Find a handbook from the "glory days of AM" 1950 or so and read the chapters on modulation and class C finals.  Quite a bit more involved than matching up a modulator and a pair of final tubes. The HW-100 normally runs at much higher plate voltage than would be adviseable for high level modulation. 100 watts input would be possible using some other power supply than the Heath, but 100 watts out just would not happen. The pi-network plate capacitor would need to be replaced as well perhaps the plate choke.  IF it is possible to supply enough drive for proper class C operation, then I am not sure about the pi-net inductor value, screen voltage, etc.  
"Can of worms"? you bet! Not impossible by any means but quite a project.   Install a relay under the chassis to unbalance the modulator and bypass the filter and your AM signal will appear at the antenna at the 15 to 20 watt level and you will be  hard pressed to tell it from plate mod. Any 800 watt or better linear amp will give you the 100 watts AM desired. 73, Gordon VE5UJ

Peter A Markavage <pmarkavage at JUNO.COM> wrote: Use it as a driver for a linear. Lots of us do that to generate a "big"
carrier on AM. I generally run my 100V at 10 to 15 watts and drive either
a SB-200 or Johnson Courier.
Pete, wa2cwa

On Tue, 21 Aug 2007 11:54:06 -0500 kd4e  writes:
> Bob,
> 
>     I am told that due to the nature of the mode and other
> factors if I want reliable communications other than very
> local (which I do) I need a minimum of 100W for AM - and
> high-level plate modulation vs the lower-level alternatives.
> 
>     Presuming the predicate to be true I really need to sort
> out the necessary mods to the HW-100 or some other more
> amenable cw/ssb tube transceiver.
> 
>     At the moment the one component that worries me the most
> is the three section air variable tuning cap -- not sure I
> can fit a larger one in there!
> 
> Thanks!  doc
> 
> > Doc,   I'd recommend you get the back issue of Electric Radio #211 
> (Dec. 
> > 2006). which describes exactly what you need with the exception of 
> being 
> > able to change back and forth between AM and SSB/CW easily.  
> Getting a 
> > 2nd radio would be the way to go.   The author didn't report 
> problems 
> > with 25w of plate-modulated AM.
> > http://www.ermag.com/
> > 
> > 73, Bob W9RAN

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