Any horizontal antenna will have a direction (angle above
horizontal) with higher power density due to the combination
of direct rays and rays reflected from the ground.
The turnstile, if properly fed, will have uniform angular
radiation in the horizontal plane. Vertical "take off" angle
will depend on height above ground and the "circular" radiation
directly up will depend again on height above ground and the
ground constants.
73,
... Joe, W4TV
On 2014-12-09 5:45 PM, Hans Hammarquist via TowerTalk wrote:
Hi Jim,
The next question then is; Do two horizontal, crossed dipoles, feed 90° out of
phase have an even power distribution across the hemisphere, horizontal across the
horizon and circular above and below or is there a direction with a higher power
density?
Hans - N2JFS
-----Original Message-----
From: Jim Lux <jimlux@earthlink.net>
To: Hans Hammarquist <hanslg@aol.com>
Sent: Mon, Dec 8, 2014 9:58 pm
Subject: Re: [TowerTalk] Dipole gain?
On 12/8/14, 6:45 PM, Hans Hammarquist via TowerTalk wrote:
That way you should
subtract 3 dB to get a comparison between an antenna gain give over
the isotropic. I was also told that two crossed dipoles were as close
to an isotropic radiator you could get.
Not really. two crossed dipoles fed in phase is the same as a dipole at
45 degrees. two crossed dipoles fed 90 degrees out of phase is
circularly polarized in the direction normal to the plane containing the
dipoles. Other arrangements of dipoles (e.g. a Lindenblad or a
turnstile) may have better circularity in some directions.
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