[ARC5] Using a power transformers as a modulation transformer.

[Fuqua, Bill L]

There was an article in GE Ham News or something like that of a single ended sweep tube plate modulator using a
TV power transformer for the output in the 60's. Don't remember all the details now. But is was similar to Heising modulation.
I think the plate voltage was applied to center tap and modulation tube on one side of secondary and PA on the other to sort of
minimize the DC flux and avoid saturation.
Bill wa4lav
  If this has been mentioned already please forgive me. I have not read all the emails.

________________________________________
From: arc5-bounces at mailman.qth.net [arc5-bounces at mailman.qth.net] on behalf of Geoff [geoffrey at jeremy.mv.com]
Sent: Friday, April 12, 2013 9:40 PM
To: jfor at quikus.com
Cc: ARC-5 List
Subject: Re: [ARC5] Using a power transformers as a modulation transformer.

Glen,

The current capability is not the issue. The DC component of the final
saturated the iron in the core.

That's why a previous poster suggested restacking the E-Is to permit an
air gap.

-John


** Or use a choke and capacitor.

Carl
===========



> Don't know about the link! However, I have used power transformers from
> tube type television sets for modulation transformers without any
> problems! At least for transformers in the 100-watt output range. Run
> the center-tapped high voltage secondary to push-pull modulator tubes and
> use the 120 VAC primary in series with the plate/screen voltage.
>
> Does the impedance always match? Of course not. However, no one told the
> transmitter that the impedances didn't match so the power transformer
> worked fine as a modulation transformer. The older power transformers had
> plenty of current capability and, at least in those that I used in the
> 1960 time frame, no problems what-so-ever.
>
> Glen, K9STH
>
>
> Website:  http://k9sth.com
>
>
> ________________________________
>  From: Leslie Smith <vk2bcu at operamail.com>
> To: ARC-5 List <arc5 at mailman.qth.net>
> Sent: Friday, April 12, 2013 3:32 PM
> Subject: [ARC5] Using a power transformers as a modulation transformer.
>
>
> Dear List-members,
> Bry Carling has a pointer (or link) on his web-site, thus:
> " How to make modulation transformers out of old power transformers -
> by WA1HLR, Tim"
>
> This link does not work.
> Power transformers don't work (usually) as a modulation transformer
> because the (transmitter final) DC current saturates the transformer
> core.
> I would be interested to get information about using a power
> transformer as a modulation transformer.
> I would be interested to hear (or read) about the relationship between
> frequency response and quality of "iron" in the transformer.
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