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I realize this isn't part of the bitx, but it was developed in the same spirit as the bitx project, so forgive me if I ask a few questions. Firstly, if anyone has built this, can you give me any advice on the output transformer. I purchased Sunil's kit, and am having difficulty fitting the #26 wire on the binocular cores for the output transformer. I have some #30. Will using this much smaller wire degrade performance very much?

Thanks

Brent

Brent:

Probably not.

A viable alternative to the small "pignose" core
is a slightly larger one two of the same size mounted
back to back, or using four FT37-43
or FT37-61 cores cemented as two pairs of
two each side by side, and made to look sort of
like a "pignose. If necessary, go to a FT50-43 or
61 toroid core. It is not too critical; what makes a difference is
the number of turns and the ratio of turns in the
output transformer. You are trying to match the AB
transistor section to 50 ohms for the antenna. Usually
that is a ratio of about 4:1...but it may not be. There is
a lot of information on the JBOT out there. Look it up for other
alternatives. All of them will work pretty well. You may also
have to add a small capacitor across the primary winding
of the output transformer to squelch oscillation. (It happens!)

I don't know what Sunil is using, but most likely it
is a type #61 core (since these are everywhere now
as they are the common core of the 300/75 ohm transformers
for TV antenna lines). The original source is on Farhan's home
page. Look it up; it is very interesting.

john
AD5YE

Thanks John

That's what I figured. I tried it with the number 30, and the amp works, but output is low. I'll try to make a different core. The instructions specify 5 bifilar turns on the primary, and 10 on the secondary, so I guess that works out to a 2:1 ratio with the center tap.

Brent

Yes, I was wondering about using a needle to get the turns nice and tight. I was also wondering, when they refer to a bifilar winding if you are supposed to make a twisted pair prior to winding on the core, or just wind two parallel wires, or if it makes a difference. Any further info would be helpful before I rewind the core.

Thanks

Brent