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Re: Topband: flag question

Subject: Re: Topband: flag question
From: Earl W Cunningham <>
Date: Wed, 5 Apr 2006 20:09:31 -0700
List-post: <>
Mike, W7DRA wrote:

" i have a flag antenna up in the woods, it is about 15x30, and i am
redoing the transformer/coax feed line. 

i wonder what would be the effect of not having a terminating resister?  
i just want it to receive, no particular direction is important "
If the resistor is shorted out (making the Flag a continuous loop), the
pattern will be very high angle on 1830 kHz.  At low angles the pattern
will be egg-shaped favoring the normal forward and reverse directions of
a Flag with about -10 dBi gain.  The impedance at the feedpoint will be
about 3 + j525 ohms.

If the resistor is removed and the wire is left open at the center of
that vertical section, the pattern on 1830 kHz will be circular and low
angle (about 26 degrees elevation) with a gain of about -5 dBi.  The
impedance at the feedpoint will be about 3 -j1700 ohms.

Another feedpoint matching system would have to be designed and
implemented because the "normal" Flag transformer is designed to match
50-ohm coax to a feedpoint impedance of 900 +j0 ohms, and that
transformer will not work for either of the above cases.

73, de Earl, K6SE
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