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Eric W. Nyman · June 1st 12, 04:06 PM

Quote:

Originally Posted by coffelt2

"it9xxs" wrote in message
...

Hi, I'm looking for a low-power modulation transformer. I'd like to
build a QRP (5W?) tube AM transmitter for the 10m band. Thanks, 73s,
IT9XXS

Are there any old tube type CB radios around?

I suppose size might matter, but sometimes old tube type
power transformers can come up with a "close enough"
impedance ratio.

Another old time solution was to find a tube type speaker
output transformer, with the secondary on an outside winding
which could be stripped away, making room to add a new
secondary. (keep a log of turns removed on the old
secondary, so a good estimate of new turns required)
(to get impedances fairly close.. precision not required)

Old Chief Lynn, W7LTQ

I have used the Vertical Output transformers from Tube-type TV sets.
They are designed to handle quite a bit of current.
Not 'Hi-Fi' tho, but Very cheap..
You can connect the modulator tube to the tap to increase the modulation for the PA tube, OR connect the modulator tube to the end of the winding and the PA tube to the tap to prevent possible over-modulation.
Both ways work.
73 de Eric / WA4HIS.

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