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Old February 25th 09, 08:07 PM posted to rec.radio.amateur.antenna
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Posts: 2,951
Default @0 Meter Vertical Collinear
On Wed, 25 Feb 2009 04:04:39 -0800 (PST), wrote:

The advantage of the half wave is exactly for its high impedance in
relation to the loss of ground. The far ground still dominates low
angle launch characteristics, but if (like the large number of radials
offers) you lose less to ground, you have more in the air in all
directions.

....
this leads to 1100Vp voltage (at 1500 Ohms). Without careful
construction, E-field at sharp edges will exceed 3000V/mm easily.
....
This
will not result in full air breakdown (due to strong nun-uniformity of
E-field, but will result in undesired corona discharge.

I would have thought they were the same. (Corona discharge is NOT air
breakdown? Is there some distinction to "full?")

However, this is not an exclusive disadvantage of a half-wave radiator
when a quarter-wave radiator can exhibit similar problems through
similar poor building practices. The same high potential "problem"
exists at the quarter-wave's distant end where the half-wave's is at
the near end, feed point. As the original poster posed this as a
single band antenna, a half wave has practical solutions if the
additional gain is deemed sufficient for the effort.

On the other hand, going from quarter-wave to 5/8ths does yield
benefit that exceeds +/- 10% or 1dB.

73's
Richard Clark, KB7QHC
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