[TowerTalk] Gap Vertical, Verticals in general

[Frank T. Brady]

Tom,

None of the responses to your thread described the vertical antenna
characteristics in quite the same way as I have come to understand them, so
I thought I'd throw mine in after the dust settled.

Regarding the effects of elevating the base of verticals:

My understanding (mostly from from the Bill Orr W6SAI book) is that the only
thing that affects the takeoff angle for a single vertical radiating element
is the electrical length of that element. The angle is lowest for a 5/8 wave
element.  Elevating the base of a vertical has no effect on the takeoff angle.

As the base of a vertical is elevated, the number of radials required to
minimize ground return losses drops rapidly from 120 (base at ground level)
to 3 or 4 (base 1/2 wavelength above ground).  The number of radials
required continues to be reduced at greater than 1/2 wavelength heights
until it is approaches zero at 1 wavelength elevation.  Greater elevations
have no additional benefit (unless, of course, they result in raising the
antenna above local obstructions).

The two books I recommend are:

The Amateur Radio Vertical Antenna Handbook
2nd Edition
Capt. Paul H. Lee, USN (RET), N6PL
Published 1984 by CQ Publishing, Inc.
Library of Congress Catalog Card Number: 74-83411

Vertical Antennas
William Orr, W6SAI and Stuart Cowan, W2LX
Published 1986 by Radio Publications, Inc.
Published 1993 by Radio Amateur Callbook
Library of Congress Catalog Card Number: 86-061499
ISBN 0-8230-8710-7


73,
 Frank T. Brady - W0ECS


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