[amsat-bb] Re: Arecibo and circular polarization using cheap yagis

i8cvs domenico.i8cvs at tin.it
Sat Apr 17 09:20:43 PDT 2010

----- Original Message ----- 
From: "Idle-Tyme" <nss at mwt.net>
To: <amsat-bb at amsat.org>
Sent: Saturday, April 17, 2010 4:51 AM
Subject: [amsat-bb] Re: Arecibo and circular polarization using cheap yagis

But what about antennas like the M2 ants where it's a balanced feed, and 
there is no + side of the element or coax?

The Original Rolling Ball Clock
Idle Tyme

Hi Idle-Tyme

The M2 antennas uses folded dipoles wich is a balanced system with
impedance of 200 ohm.

In order to transform the impedance from 200 to 50 ohm and change
from a balanced system (the folded dipole) to a unbalanced system 
(the 50 ohm feed line) a 1/2 electrical wavelenght of 50 ohm coax
cable called balun is connected with the inner conductors across the
dipole studs.

the braids of the 1/2 electrical wavelenght coax balun are soldered 
togheter with the braid of the 50 ohm coax feed line and grounded
to the center of the antenna boom.

The side of the folded dipole connected to the inner conductor of the
feed line is the (+) side of the element.

I hope this helps

73" de

i8CVS Domenico 

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