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Old August 9th 07, 08:03 PM posted to rec.radio.amateur.antenna
Highland Ham Highland Ham is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 250
Default Building a T2FD antenna

The terminating resistor of a B&W antenna is 600 ohms resistive i.e.
there is a 600 ohm resistor connected to the ends of the folded dipole
antenna. It's purpose is to swamp the current leftover when the standing
wave is formed. The balun is of necessity a 12 to 1 ratio balun. Other
values may be used to other effects.
The biggest problem is the balun. I haven't seen any specs for making
one. The resistors need to be carbon non inductive high wattage.

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A 12:1 ratio balun is decribed by Jerry Sevick , W2FMI in his book :
"Building and using Baluns and Ununs" , pages 54-55
It is in fact a combination of a 1:1.33 Unun and a 1:9 (type Guanella)
Balun , hence for an impedence transformation of 50 Ohms unbalanced to
600 ohms balanced. The unit has 4 toroids.

The above book : Library of Congress Catalogue Card Number 94-69520
ISBN 0-943016-09-6



Frank GM0CSZ / KN6WH