[Antennas] Half-Square Question

Sat, 1 Nov 2003 12:41:22 -0500

Dear Ron,

Don't feel bad - it's not obvious how the half square works.

The two vertical portions are forming a 2 element vertical beam that has its
favored radiation broadside to the flat top.  The flat top is nothing but a
1/4 wave delay line that causes the phase relationship between the two
verticals to be such that they cancel each other in their plane. I.e., there
is a null in the pattern along the direction of the two verticals.

Think about it this way - in relation to the signal in the directly fed
vertical, the other vertical gets its feed 1/4 wavelength (90 degrees) later
in time. Then, that signal has to travel another 90 degrees through space in
order to get to the directly driven vertical which is 1/4 wavelength away.
As the two signals combine at the location of the directly driven vertical,
they combine 180 degrees out of phase (cancellation). But that only occurs
in that plane. In the perpendicular direction the two signals arrive at any
distant point in phase (reinforcement).

All of this presumes that the coax feeds the flat top from the center
conductor and the directly driven vertical from the shield connection.

Sounds good to me - let's see if the rest of the world agrees!

Bob Lay (W9DMK) in Dahlgren, VA
http://www.qsl.net/w9dmk
----- Original Message -----
From: "Ron Evans" <[email protected]>
To: <[email protected]>
Sent: Saturday, November 01, 2003 11:52 AM
Subject: [Antennas] Half-Square Question

> At the risk of exposing my considerable ignorance yet again, can someone
> clear up for me a question about the half-square antenna.  Does the
> center conductor of the coax attach to one of the vertical 1/4
> wavelength portions or to the 1/2 wavelength flat top portion?  Why?
> And will maximum radiation be broadside to the flat top or parallel to it?
>
> I've seen it both ways on the Internet.  Some sites say the favored
> direction is broadside to the flat top, and others indicate that the
> favored direction is "along" the flat top.  Perhaps the antenna will
> work either way?  And changing the point at which the center conductor
> attaches changes the favored direction?
>
> Help!
>
> Thanks in advance for educating me "kindly."
>
> 72/73,
>
> Ron - KD5S
>
>
> ******************** Ron Evans ************************
>    KD5S  (ex K5MVR) - Loving the "glow"  since 1957
>         Fort Worth, TX  "Where the West Begins"
>            mailto: [email protected]
>        http://www.geocities.com/sweetvengeance
>        Adventure Radio Society (ARS) - #1595
>                 http://www.arsqrp.com
> *********************************************************
>
>
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