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Wind your own transformer

By George Dowell, K0FF
Topband Antenna mail list, September 16, 2000

Tommy, WD4K, who was experimenting with some Pennants, asked me to wind him up a couple of transformers.
Transformers can also be bought ready made, among others from Array Solutions.
They ship international, and accepts all major credit cards.
The small cores that I normally use weren't big enough for the large number of quadrafillar turns needed to match 75 Ohms to 900 Ohms.
So I took the advice of Mauri, I4JMY, and went to a much larger core, and a smaller number of turns but with larger wire.
Well, with the FT-140 J's that were on hand 1.4" dia x .9" tall and u=5000), Mauri's recommendations were darned close.

Inside transformer.
I wound up liking a 3T primary and a 7T secondary for the 50 to 470 Ohm Beverage transformers.
For the Pennant I settled for 3T/11T for the 75/900 transformer.
Both worked well on the lashed up test setup that I threw together this morning.

With the smaller turns count working so well, I went back to the smaller cores for Tommys units (FT-50-75's) and had plenty of room to spare. That's his in the glue drying fixture on the left of the '259 in the photo.
You can also see some of the jigs that make the cut and try method a little easier.
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