[Amps] Modulation Transformer(s)

[Mike Sawyer]

Yeah, but sometimes it feels good to do something classical. If I wanted to 
go real high-tech,  I could use a bunch of FET's and run class E for super 
efficiency. But I feel "Real Radios Glow in the Dark."
Mike(y)
W3SLK
----- Original Message ----- 
From: "R.Measures" <r at somis.org>
To: "k7fm" <k7fm at teleport.com>
Cc: <amps at contesting.com>
Sent: Sunday, February 20, 2005 5:42 AM
Subject: Re: [Amps] Modulation Transformer(s)



On Feb 19, 2005, at 5:25 PM, k7fm wrote:

> First, this is an amplifier question - even though the amplifier part
> in
> question is from a class c amplifier rather than a linear amplifier.
>
> One of these days I plan on building a 500 to 600 watt plate modulated
> rig.
> I have all the parts except the modulation transformer.  Finding a 300
> watt
> transformer normally involves the expenditure of about $150 or more.
> I am
> considering another option - that of using 2 modulation transformers
> from an
> ART-13 in parallel.

Low-level modulated, linear-amplified AM has noticeably less IMD
products than plate modulated AM.  Fuel injection is noticeably better
than carburetion.  Mo' older is not always mo' betta.
>
> The normal arrangement in an ART-13 is P-P 811 tubes modulating an 813.
> What I would propose is P-P/parallel 811 tubes modulating push-pull
> 813s.  I
> realize that there may be no real advantage to running the 813s in
> push-pull, but I have the parts and it sounds cooler (only for one
> band, so
> bandswitching is not an issue).
>
> I already have the ART-13 transformers.  They are beauties.  The
> additional
> advantage of the ART-13 transformers is that there is an extra winding,
> which would be used for feedback to the earlier stages to reduce
> distortion.
>
> I have hunted numerous books and never found it discussed.  Anyone
> done it
> before.  Any concerns?  Are resistors needed to match loads?
>
> 73,  Colin  K7FM
>
>
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Richard L. Measures, AG6K, 805.386.3734.  www.somis.org

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