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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