Dave
I am now proceeding with the installation or a "Free" US Tower
TMM541 tower for my KT34 tribander, M2 6M7JHV and a pair of 2M-5WL's
on a 20' Mast.
Like you I have been considering mounting and feedline problems for
the new tower. My feedlines are somewhat more Modest. The existing
Rohn 25 next to the new one currently has the KT34 (with M@ updates
and the 6M7JHV feed by 9913 for 6M and RG213 for HF and another run
of 213 for a G4RV wire.
The New runs will be 7/8" LDF 5-50 for 2M and 6M one run of RG 213
will be used for the Tribander and the other for the G5RV. The 9913
fromm the existing tower will feed a 6M M2 HO loop for omni use and
other runs of either 213 or Andrews superflex installed in the 3"
conduit as space allows.
My runs are about 100' from the shack to the base of the tower and
will terminate in a 10"x12"x5" Weatherproof Steel Box. That said
here in Central Florida's Lightning capital of North America, My
installation differs in that instead of Type-N feed through bulkhead
connectors I used Gas tube Lightning arresters through the wall of
the weatherproof box. After looking at Polyphasers and discounting
for price and power level issues I settled on AES SPN and SPU units
(see http://www.aesham.com/display_pages/aesspu.shtml ) I also
replaced the inner painted steel mounting plate with a copper sheet
and lined the sides of the box with copper sheet before drilling the
5/8" holes for the lightning protectors. The inner plate, side
plates are all bonded with copper straps.
For the Rotator cable and 2M PreAmp power and switching relay lines
a PolyPhaser 8 wire unit was installed in the box.
Cables to the shack will be routed into the box through a 3" PVC
conduit through a hold cut inn the bottom of the weatherproof box and
a 3" PVC Threaded bushing. The Switching Relay and PreAmp for 2M
will be mounted in the Box on the copper Back Plate for
grounding. The box will be mounted to the Tower's Slab and bonded to
the tower's ground rods with copper straps. The tower grounds are 2
- 32' ground rods and one 20' length of 1/2' cooper tubing washed in
all bonded by 1/2" copper tubing in a ring around the tower's base (
did I mention the Orlando Florida ares is the lightning capital of
North America?). One of the 32 ' ground rods is on the existing
tower which will be taken down when antennas are moved to the new tower.
The feedlines are being moved underground for lightning reasons. The
3" conduit will run underground from the tower base to the house and
about 8' up the side of the house in under the eves of the house
through the pool screen enclosure as lightning doesn't like to go up
after coming down the tower . Phasing lines for the 2M beams to the
M2 2 port power divider are LMR 400 and runs down the tower are 9913F
for all the runs around the rotator. I had considered Andrews 1/2"
SuperFlex but thought the repeated flexing of the feedline by the
Prosistel PST 2051rotor's 500 degree range of rotation would cause
the feedline to fail.
I have digital pictures of the box and will send to your e-mail off list.
Like you my project is in the "Starting to look like more then a pile
of parts here now" phase.
VRY 73
Bob Cumming
W2BZY
QRV 160m-9Cm + 3Cm
from EL98hr
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