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If you cannot lay the radials out in a symmetrical radial pattern, don
’
t worry too much
-
it will distort
your omni
-
directional pattern slightly but won
’
t reduce your efficiency very much. Lay the radials out in the
best manner possible given your situation. There are various ways to accomplish laying a radial system, in-
cluding turning corners, etc. Turning a radial back towards the antenna and running it until the obstacle that
prevented a radial there is encountered (with about a
10”
radius) is a good way to increase the effective
shield area.
Good results are limited only to your creative energy and determination! Be aware that very high volt-
ages can exist at the ends of radials, so be certain that no one can come into contact with them. It is a good
idea to use insulated wire to protect from corrosion, and don
’
t bury the radials any deeper than necessary,
one to two inches maximum. In the manual you will see we suggest mounting the EHU box so the ground
stud is no more than
8”
-
10”
from the radial field.
Any straight vertical wire going from the EHU to the radial field adds to the antenna length and causes
a mismatch at higher frequencies because it causes off
-
center feeding. When a good radial field is present
verticals work much more efficiently and predictably.
Elevated Mounting:
If you elevate radials even a few inches off the ground the capacitive losses go down dramatically. On
80m 5 feet is all you need to get a drastic reduction in losses, thus allowing the use of many fewer radials.
Once the antenna is elevated it is much easier to get reasonable performance with even one .25 wl radial!
With one radial the antenna is no longer omni
-
directional, the side with no radial is down by 4 dB, that ener-
gy now appears at high elevation angles on the radial side and can be advantageous for close in contacts (0
to 400 miles).
Once you elevate a vertical, two .25 wl radials work very well. It is important that you try to keep a
180° angle between the two (opposed, directly in line) for the best pattern. You will need two .25 wl radials for
each band you intend to use. Spread the radials out as far as possible to reduce interaction, if they are less
than a foot apart it can be difficult to get a good match on all bands.
In Rudy Severns articles he is a big proponent of at least four up to 12 elevated radials, because the
antenna becomes much less affected by nearby objects and the gain is better. His contention is that it is ac-
tually easier to just cut 25 to 30 30ft radials, it is then easier to deal with radials all the same length without
the need to cut them to different lengths and then have to arrange the pairs 180° from each other. The down-
side is this is 665ft more wire than a 2 elevated radials per band system suitable for 40
-
6M. The two elevated
radials are just slightly down in gain. This system will now work well at any frequency from 40m—
6
m, for
80m double the length of the radials. As more radials are added the impedance of the antenna drops, over
perfect ground a vertical is 36 ohms. If you put up a vertical with a poor radial system you usually get a good
match because the ground LOSS adds to the 36 ohms to get you at or near 50 ohms, but with a big drop in
signal strength.
To raise this low impedance closer to the desired 50 ohms you can angle the radials downward, this
raises the impedance of the antenna as you increase the angle downward. Graph 4 (next page) shows the
approximate relationship of radial angle to impedance:
COUNTERPOISE/RADIAL SYSTEM OVERVIEW
