W8JI wrote:
>It would be very interesting to see results of an A-B test between a
>Beverage over a counterpoise, and one not over a counterpoise, at
>the same location.
>Has anyone actually A-B'ed a system like this, and seen a clear
>difference with and without a counterpoise, which is certainly what
>any metal fence would be....grounded or not.... ?
Terry,
Maybe you can forward this to the Topband Reflector for me:
At HZ1AB we recently had the following experience with a Beverage
project. The Topband guys may find our single-wire counterpoise
solution useful.
The case is similar to the Beverage installed on top of a page fence
- but different.
Our case is a double wire Beverage that is installed some 3m up on
horizontal plastic pipes that are fixed to a high concrete perimeter
wall, some 300 m long. The perimeter wall may very well contain its
share of rebars. One wire is some 0.2 m from the wall and the other 0.3m
further out.
The earth is extremly poor!
The Beverage operates as a standard two-wire type that we can switched
forward and reverse directions. The forward direction has no resistor at
far end but one wire is connected to earth and the other is open ended.
At near end (feeder end) an earth is required for the arrangements. The
feeder has a separate earth, and the primary and secondary
windings of the transformer are electrically separated.
Initially, the Beverage did not work very well. As the earth is very
poor, my reasoning was that it may be a useful to connect the earth at
both ends together, to ensure they see the same electrical ground
reference potential. Unfortunately, this 'connection wire' on the ground
could also act as a counterpoise and potentially ruin the Beverage
operational characteristics.
Nevertheless, I tried a single wire on the ground connecting each of the
Beverage earth ends. The resulting signals increased and the noise level
is now much lower. I do not think that the wire acts as much as a
counterpoise since the area (seen the way the received signal sees the
antenna) of the wire is very small in comparison to the rest of the
ground surface. The Beverage radiation characteristics are preserved.
73, Thomas SM0CXU @ HZ1AB
Thomas
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