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Old February 15th 06, 09:11 AM posted to rec.radio.amateur.antenna
Geoffrey S. Mendelson
 
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Default 300 ohm folded dipole from ARRL Handbook, early 1990's

Hi, the early '90s ARRL handbooks had construction information for a
simple folded dipole made of 300 oHm twinlead. The article was not in
the '96 edition or later.

The antenna was made of 300 ohm twinlead. It was fed in the center by
a 300 ohm twinlead feeder to a matching capacitor which made it aproximate
50 ohms. The capacitor could be either a regular capacitor (I used silver
mica WWII surplus) or a "stub" of more twinlead.

At the end of the feed line, which was part of the antenna, you could
attach it directly to a 50 omh unbalanced transciever or a 50 ohm coax
of any length.

The length of the antenna was one half wavelength without the velocity
factor and then shorted at the wavelength points compensating for
the velocity factor.

For example, if it was 10 meters long for a 20 meter dipole, the shorts
were about 4 meters from the center for twinlead with a velocity factor
of 0.8.

If anyone has a copy of the article and could scan it for me, I'd
appreicate it, or even better yet, a pointer to an online version
of it.

Thanks in advance and 73,

BTW, if you are also in Israel and asking yourself "where does he get
the twinlead"? I don't. I brought it with me when I moved here in '96.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM
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