[AMRadio] Building


Mike Sawyer w3slk at hughes.net
Sat Dec 1 20:56:11 EST 2007


Geoff said:
A fine and fitting job for the RCA 1:1 modulation transformer, with
5,500 ohms on primary and secondary.

**I wish I had said transformer.


If you want to get 'close enough', then, at 1500v, run 4 100TH's in
push-pull parallel in the modulator for effectively 4400 ohms,
plate-to-plate impedance, according to the Eimac tube data sheet.
According to it, a pair of 100TH's in AB(1) has a plate-to-plate load
impedance of 8800 ohms.  That's kinda high to work into a 5500 ohm
transformer.  4400 ohms is -much- closer.

**Doesn't that make quite a bit of Cg-p? You would need some large 
neutralizing capacitors because of the combined C of the parallel tubes.
Mod-U-Lator,
Mike(y)
W3SLK




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