your own transformer
By George Dowell, K0FF
Topband Antenna mail list, September
Tommy, WD4K, who was experimenting with some Pennants, asked me
to wind him up a couple of transformers.
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.
can also be bought ready made, among others from Array
They ship international, and accepts all major credit cards.
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.
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
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.