The source I have on this "aerial" is the RSGB's "Amateru Radio
Techniques", Seventh Edition, edited by Pat Hawker, G3VA.
In Section eight, "Aerial Topics", , page 265, there is a section on
"Aerials Using 300-ohm Ribbon Feeder". From the article:
"Two simple aerials featuring 300 ohm feedr are shown in Fig. 2. Fig 2
(a) is the "T2FD" (terminated tiltes folded dipole). With the
dimensions given, it should provide nearly omni-directional radiation on
all bands from 3.5 to 28 Mc/s, although this aerial appears to be
appreciaably down compared with dipoles, and is not recommended, except
where space is at a premium. Wattage of the terminating resistor is
about one-third of the DC input to the transmitter."
The diagram, Fig. 2, shows a wide-spaced folded dipole, with an 18 inch
spacing between conductors, an overall lentgth of 47 feet, the high end
up 32 feet, and the low end up 6 feet. It is fed in the center, on one
leg, with a "300 ohm feeder", and directly opposite, on the other leg,
there is a 400 ohm non-inductive terminating resistor. The antenna fits
in a 40 foot length. Figuring a 50% efficiency for the "average"
transmitter, the terminating resistor would need to be about 3.3 watts
for a QRP version of this "aerial"...
There have been several modelings of the T2FD in the past, with results
posted on the QRP-L a couple of times, and it is down some 5 - 6 dB from
a dipole, as I remember.
This could be a challenging antler to run on QRP, as you can be in the
milliwatting class of performance while running almost a "QRP Gallon".
Two for the price of one, sort of...
I will play around with the text editor, and see if I can make an ASCII
"drawing" of sorts on this antler. Also, my SpellChecker chokes on
"aerial" unless I leave it in quotes. Strange...
72/73, Keith, WB2VUO, QRP-L #582, scQRP 40, Tech Specialist (ARRL/WNY),
ARRL Life Member, VP/BARK, Beacon Chaircritter, Rochester VHF Group
Trustee, KB2YTW/B 10 Mtr QRPp Beacon (250 mW @ 28.2870 MHz)
"In the Depths of the Great Bergen (NY) Swamp...FN13ac"
Packet - wb2vuo@w2im.#wny.ny.usa.noam
Email - wb2vuo@juno.com
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