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Old February 3rd 12, 01:35 AM posted to rec.radio.amateur.antenna
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Default effect of close property fence on dipole arrays and solution?


"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


 
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