Jason,
An end-fed antenna that is an integral multiple of 1/2 wavelength will
present a very high impedance. An end-fed antenna that is 1/4, 3/4, 5/4 etc
wavelengths long will present a low impedance more suitable for direct feed
from your rig. The impedance of a 1/4 wave antenna end-fed against ground
or a counterpoise as you suggest would be about 35 ohms and purely
resistive, half that of a center-fed half wave. If your rig is designed to
match a 50 or 75 ohm load, you could increase the length of the antenna to
about 0.28 wavelength for 50 ohms or to about 0.3 wavelength for 70 ohms.
The antenna would show some series inductive reactance at those lengths
which could be tuned out with a series capacitor.
A vertical quarter-wave will have a reasonably low angle of radiation and
will be good for low-angle propagation usually associated with longer
distance contacts. Increasing the height of a vertical fed against ground
up to 5/8 wavelength will further enhance the low-angle radiation. Above
5/8 wavelength height, a second, high-angle lobe develops and the low-angle
radiation suffers.
A good reference book on verticals that you may be able to find is The
Amateur Radio Vertical Antenna Handbook by Capt. Paul H. Lee. It is
published by CQ Communications, Inc, 76 North Broadway, Hickville, NY 11801.
It is a paper-back and not expensive.
Hope this helps,
Jim, W8KGI
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