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[TowerTalk] Full wave loop on 80m : Impedance 50 or 75 Ohms??

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Subject: [TowerTalk] Full wave loop on 80m : Impedance 50 or 75 Ohms??
From: (realex)
Date: Tue Jan 28 20:19:50 2003
A vertically mounted full wave loop that is rectangular ( twice as high as
it is wide) will have a feedpoint
Z of around 40 ohms when fed in the center of the short side nearest the
ground.  Since you state your loop is
 horizontal and 1/8 wavelength high, I would think the feedpoint Z is less
than 40 ohms.  If that is the case,
the 50 ohm line is the better choice.
73, Bob, W5AH

-----Original Message-----

I have been using Full wave loops on 80m since 1987 and have always used 75
Ohm coaxial cable as feedline without a Balun.  I know of other hams that
use a Balun on a full wave loop. My Loop is Rectangular in Shape and fed in
the center of one of the shorter sides. The Antenna is terminated with a gap
of around 3 inches between the ends.
This was how it was described , for a German Quad antenna which is a Full
wave loop in a Diamond shape terminated at one of the sharp pointed
ends..The German Quad was Quoted with an Impedance of roughly halfway
between 50 & 70 Ohms Impedance.. My Quad antenna is 33 feet high at all 4
points.  Any Comments on what impedance this Antenna May be at the feed
point and how to feed it with Coaxial cable... I am about to run ALL new
cables thru the roof of My House and I'm wondering whether to use 50 or 75
Ohm Cable...
Lee Noonan  VK2LEE

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