[AMRadio] Re: RCA 1:1 mod xfmr

Geoff/W5OMR ars.w5omr at gmail.com
Sun Dec 2 03:56:10 EST 2007

Mike Sawyer wrote:
> If its the one I'm thinking of, I have one of those. It has a tertiary 
> winding for the screens and a funky secondary max. I of 0.193 A(?) The one I 
> was looking for but needs repaired is 10300 Pri. and 4300 sec. If memory 
> serves me, it was used in a KW transmitter. Mine goes in my RCA ET-4336F 
> transmitter. A rig that uses 813's X 805's for 250 watts, (very lightly 
> rated.

Same transformer.  The one I have actually is stamped "0.198mA DC".  
Others I've seen, state "200mA" as the max secondary current.

I'm still not sure if that's where saturation of the core starts, or 
that's where saturation of the core -is-.

Otis/K5SWK uses the same transformer in his single 833 x 833's rig.

I've ran a pair of 250TH's on one, modulating another pair.  Also used 
that same transformer with push-pull 811's, and then later changed to 810's.
It took (4) 810s, with that transformer, to get the same amount of audio 
I was getting from a pair of 811's.

then again, not too sure of the condition of the 810's.  They came out 
of a foot-locker that John/W5MEU had stashed away for so long, he forgot 
about 'em (and that's not like John!)

I ran two on the positive side, and one on the negative side.  positive 
peaks were about 3:1.

My next modulator is going to contain (4) 811's in push-pull parallel.  
Maybe (6), at 1250v on the plates, and (-)0v bias.

That should take care of any asymmetrical audio.

Driving your AM Rig without a scope, 
is like driving your car at night, without headlights. (K4KYV)

73 = Best Regards,

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