The holy goal of resonance has little to do with the performance of a plain
0.5 WL dipole. Almost all of the power delivered will be radiated. What is
sure to reduce performance of a 20 meter dipole is being only 6 meters above
ground. 6 meters is about 0.28 WL and thus most of the radiation is towards
the zenith. This will be true even if you prune the length of the antenna
to have no reactance (to be resonant) at your operating frequency.

The old tale of resonance equating to enhanced performance is, to say the
least, an exaggeration.

We do not know how high the fence is nor what sort of grid it has. Since
the antenna can not be moved horizontally, not much point in speculating
about the effect of the fence.

What will improve performance is to move the dipole higher.

73, Mac N8TT

"Sal" wrote in message ...


"Bill Peters" wrote in message
...
I put up a 20 meter dipole array a while back and I don't seem to be
receiving the greatest signals. The height is fairly low, about 20', and
one part of the array is fairly close to an aluminum fence I have
surrounding the property. I'd say the southern leg of the array is about
25' away from the fence. So I ask the question: what effect can fences
have on antennas and what are some possible solutions? I can rule out
moving the antenna because I lack the room to move it any further away from
the fence.

Thanks,
Bill

Since length formulas treat your installation as being close to ideal,
consider that the antenna, being physically lower than ideal, may be too
long for 20m work. I made that mistake with a 40m dipole some years ago and
had to cut it shorter to reach resonance, due to the effect of the
too-nearby earth. (A tuner makes your radio happy but won't solve inherent
problems.

If the the antenna sees that chunk of metal fence as an upward extension of
ground, that just adds to your problem, although 25' away doesn't sound like
a big deal.

Have you access to an antenna analyzer that will clue you to the resonant
frequency of your dipole?

Know also: being too close to ground will cause the pickup pattern to favor
upward, vice off toward the horizon



J. C. Mc Laughlin
Michigan U.S.A.
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