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Author Topic: Antenna hot point top or bottom ?  (Read 1254 times)
SV1ENS
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« on: December 16, 2008, 07:34:06 AM »

Hi all,
In the antenna handbooks where the inverted V antennas are described the reason for an inverted scheme is the hot point of the antenna being higher than the endpoints of the elements.

So why are antennas like the Diamond HFV5 build like a normal V Huh

73
Demetre - SV1ENS
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WB2WIK
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Posts: 20595




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« Reply #1 on: December 16, 2008, 01:28:49 PM »

There's no "hot point."  A current-fed antenna like a 1/2-wave dipole or inverted vee (or non-inverted vee) has its current maxima at the feedpoint, and its voltage maxima at the antenna ends (tips).  The tips or ends are much "hotter" with respect to the potential for causing arcs or fires!!  However near the center of the antenna (high current point) is where most of the work is done.

The Diamond (and other) rotating "vee" antennas are designed as they are so the elements clear other obstacles such as other antennas below them, chimneys, ventpipes and other things on "roofs," etc.  They work fine if you install them "upside down" so the highest point is the center, if you wish; they're just more difficult to use that way for most people.

The difference in "height" in the case of that design is only a few feet if you mount it normally or upside-down.

WB2WIK/6
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KF7CG
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« Reply #2 on: January 02, 2009, 10:23:13 AM »

The placement of the high-current point does help occassionally. For what it is, a semi-limited space, shortend verticle, the MFJ 1798 performs quite nicely do to the high current area being at the top.

Now if the counterpoise weren't quite so sinsitive to wind damage.

KF7CG
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