After 17 years of operating with longwires, dipoles, and a vertical,
I'm finally getting ready to put up a tower and beam antenna. Just
wanted to run my proposed setup by the list and see if I've overlooked
anything. I'm a very experienced operator, but a complete novice when
it comes to tower/beam installations! :) Thanks to all who previously
encouraged me to get rid of the vertical and go for the "low" beam!
Due to power lines and property lines, a standard tower is not an
option, so I'm opting to go with a Glen Martin Engineering 17.5'
roof tower. It's built with 6061-T6 aluminum, does not require
guying, and has a base width of 32". The rotor shelf sits a little
over three feet below the top of the tower and also has a top
plate for a thrust bearing. I'm also getting the GME thrust
bearing and a 5' x 1.92" OD 0.145" wall medium duty mast. I'm going
with an aluminum mast because I want to try and keep the weight down.
This mast will leave about 2 feet of mast protruding from the top of
the tower. I don't want to go nuts with sticking a ton of mast out of
the top of the tower, so I figure two feet is plenty to mount a beam and
2m/440 vertical. The point where the tower will be mounted is about
12' high, so the antenna will be at the 30' level. My house is about
30 years old and the roof was redone about 9 years ago (asphault type
shingles) and is in great condition.
I want to go with a Force-12 C4-S which is the shorter boom (12') version
of the C4. I don't mind giving up a few tenths of a db to have
an antenna which won't look as obnoxious to the neighbors. I'll use
two Force-12 B-1 baluns and two 70' runs of 9913 coax. I also have
a 2m/440 Diamond D-100 vertical I'll put on the very top. I've
chosen a Hygain Ham-IV rotor. I'd like to get a rebuilt one from
the RotorDoctor, but he has a pretty long waiting list right now, so
I'll probably just get it new. The Ham-IV will handle up to 15sqft
and a C4S is only 6sqft, so there's no problem there.
Here are a few questions I have:
The standard 8-wire rotor cable seems to be 2-#18 & 6-#22. Is there
any reason I should get bigger gauge rotor cable for a Ham-IV? I
also plan on getting the "Quick Connect" type connectors for it.
Should I run the coax and rotor cable along the top of the roof to
one of the vents on the end of the house, or should I drill another
hole in the roof for all the cables? If I go thru the roof, I assume
I should use some sort of tubing with a 180 degree turn on top to
keep water/moisture out?
I have overhead copper plumbing in my attic close to where the tower
will sit. Is connecting to it a good way to ground the tower?
Thanks for any comments/suggestions!
73 de Doug, N6RT
Doug Brandon http://www.kaiwan.com/~dab firstname.lastname@example.org
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