We have several of the center fed Force 12 verticals of the Sigma V class
for a project at work.
They were also used for a ham operating event on the bands 20m and up.
They work great, are very easy to use and can be put up very fast. Assembly
is speeded by the use of wing nuts.
Our models did condense salt water overnight at the beachside test site.
That is easily removed from the "radome' covering the loading coils, relays
and centerfeed point by drilling a weep hole in the bottom of the cover
housing. In sustained salt water atmosphere you would have to rinse out the
housing with fresh water, but this is commonly done with other commercial
antennas in seaborne service.
They are very good shortened dipoles, using a combination of center loading
coils and horizontal rod capacity hats to resonate the 12 foot length as a
20m dipole. The furnished control cable to the relay switch box is 50 feet,
so you might have to add some for other installations.
The coax feeder has ferrite beads over it at the feedpoint end to remove any
chance of RF on the outer shield back at the rig.
-Stuart
K5KVH
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