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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