Other Types of Towers
Attachment of Feedline
When installing the TH7DX on a guyed
tower, you may wish to use a different guide
system. If you have insulators on your guy
wires, you will need to keep the antenna away
from the guy wires as well as the tower. You
may wish to use two ropes attached together
at the top of the tower and attached to the
ground about 15 feet apart. These two ropes
can then be used to slide the antenna on as it
is also being lifted. The two ropes will need to
be far enough from the tower base to allow
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Use a good quality 50 ohm coaxial
transmission line such as Time RG-213/u
(solid), Belden 8237, 8367 or 9251 (solid). Take
extra care when soldering connectors to foam
dielectric coaxial cable. Weatherproof all
connectors which will be exposed to rain or
ice, with Coax-Seal® or another similar
Attach the transmission line to the BN-86
balun and tighten the connector securely. Tape
the coax to the boom and mast to ensure good
strain relief.
Lightning Protection
VSWR Curves
For proper lightning protection, you must
ground your antenna supporting structure.
Grounding will ensure noise free operation
and low VSWR. A proper ground consists of a
1/2" x 8' copper clad steel ground rod driven
into the ground approximately 12 inches
away from the concrete tower base. Connect
the tower to the ground rod using #8 copper
wire and commercial non-corrosive ground
clamps.
These VSWR Curves are typical for the antenna
mounted 70 feet above the ground, horizontally
polarized. Similar curves can be expected for
this antenna mounted between 30 and 100 feet
above the ground. DO NOT TRY TO TUNE
THIS ANTENNA FOR LOW VSWR AT
GROUND LEVEL. Higher VSWR can be
expected if mounted at less than 30 feet or
above a roof or large metallic structure. Forty
(40) and eighty (80) meter wire dipoles should
be kept at least 6 feet below this antenna. Guy
wires should be broken up into non-resonant
lengths (less than 12 foot lengths) and insulated
from the tower if mounted within 10 feet of the
top of the tower.
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