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Stick
with the 34/8 turns
By Earl Cunningham, K6SE
Topband Antenna mail list, November,
2000
Gerry Kersus, W1GD posted a message about a problem matching his
Pennant antennas using the transformer described in the July 2000
issue of QST. Using his Autek RF-1 analyzer, he measures an SWR
of over 3:1, either with antenna or with a 900 Ohm resistor as the
load for the transformer.
Although the 34/8 turns ratio of the transformer theoretically should
match a 900-Ohm load to 50-Ohm coax, several others have mentioned
this same "problem" to me. W7IUV has tried numerous transformer
designs, but he says that the one described in the QST article is
the only one that makes his Flag antenna "come to life" and perform
as it should, and without hearing compuiter "birdies" (which are
apparently picked up by the feedline when using his other experimental
transformers).
Two transformer manufacturers are now selling the transformer
made exactly according to the QST article, with many apparent happy
users:
Bob, K1FZ makes the KB-5 transformer for Pennants, Flags, etc.,
and can be contacted via e-mail at k1fz@agate.net.
Jay, WX0B sells one made by George, K0FF. Jay can be contacted at
wx0b@arraysolutions.com
or you can visit his Web site at http://www.arraysolutions.com.
Until a better transformer that performs as well or better
than the one described in the QST article surfaces, I recommend
that you stick with the 34/8 turns ratio on the Amidon FT-140-43
core and ignore any SWR results.
W1GD also mentioned that his Pennants were 28 feet long. The correct
dimension, from the point to the vertical side, is 29 feet.
Anyone using EZNEC version 2 or 3 that wishes to look at all of
the designs (Pennant, Flag, Diamond and Delta), send me a request
via direct e-mail to k6se@juno.com
and I'll send the EZNEC model files to you. |
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