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Re: [TowerTalk] Slopers, half slopers, (using the tower)

To: "Tower (K8RI)" <tower@rogerhalstead.com>,<towertalk@contesting.com>
Subject: Re: [TowerTalk] Slopers, half slopers, (using the tower)
From: "Tom Rauch" <w8ji@contesting.com>
Reply-to: Tom Rauch <w8ji@contesting.com>
Date: Sun, 26 Sep 2004 04:12:14 -0400
List-post: <mailto:towertalk@contesting.com>
Roger,

Every antenna fed with a two conductor transmission line,
even coax, must have equal and exactly opposing direction
currents in the two conductors of the feeder or the feeder
will radiate.

That means your tower would have the same current at the
attachment point as the half-sloper wire, and the tower
would radiate also. The amount of radiation, since current
is the same, would depend entirely on the spatial distance
the current is distributed over.

I often call them sloppers, not slopers, because they are a
sloppy system design that generally works by chance. Antenna
results largely vary with what is on your tower and how tall
your tower is (and how the base is grounded). You'll get all
sorts of answers from "they don't work at all" to "they are
the best antenna in the world".

Since they depend on the luck of the draw as to what is on a
tower at what height, you really need to model the entire
tower and everything on it. Short of doing that, just try
them and see.

Half-wave sloping dipoles are also similar. Some towers can
act like a director, some like a reflector. Some like
nothing at all.  Any slopers installed in other directions
can , through careful planning, be intentionally made into
"reflectors". This is generally a much better system.

What you are actually asking is how a random sloppy system
that causes high currents in the tower and everything
attached to the tower will work compared to a much more
predictable planned sloped dipole antenna system. The answer
to that is either try it and see, or model it. My money
would be on the results that a slopper won't work nearly as
well as the slopers you have.

73 Tom


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