I am not sure, but I think if you look at the Hand Book It will state that you
do not want the tower or anything else to be grounded that goes through
concrete. The reason being that a hit from lightning
Will cause the concrete to explode. If I am wrong someone please let me know !
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of ke2d@comcast.net
Sent: Thursday, March 11, 2010 3:44 PM
To: towertalk@contesting.com
Subject: [TowerTalk] tower & antenna project questions
Good afternoon. Finally, the 3rd sunny day in the 50s here in NJ, and time to
start the antenna work! Hopefully we'll be pouring concrete in another week or
two for the new tower. Nothing like having a new tower delivered with 24" of
snow on the ground! Now,......
I am looking to purchase a few 6m/2m/440 yagis to stack above my HF antennas.
In my last installation, I used Cushcraft antennas - 13B2 for 144, 719B for
440, and A506S for 6m. The VHF/UHF will be vertically polarized, as I work
more FM simplex than SSB. 6M, however, will be horizontal for SSB DX. This
time I am now looking at the M2 stuff, namely a 2M12 for 144, a 440-18 for 440,
and a 6M7 for 6m.
Does anyone have any recommendations of one over the other (Cushcraft vs. M2),
or recommend any other manufacturers for VHF and UHF yagis?
Also, I plan to stack a Hy-Gain 7-3 along with a TH-11DX. I was thinking of
placing the 40m beam above the TH11, as the TH11 has the higher windloading.
Anyone have any comments on which should be on top (am I correct in placing the
heavier antenna lower?), and also how much distance I should allow between the
TH11 and 7-3 40m antenna so as to minimize any potential interaction?
In addition, I need to run grey conduit under ground from the base of the tower
to where the cables will enter my home. I need to run 9 coax cables, and a
rotor control line. 10 cables total. Each run will be approx. 210ft. 100ft up
the tower, then 50ft from the tower to the house, then 50ft along the basement
and up into the shack, then 10ft or so for movement in the shack. Due to the
long runs, I was planning on going to LMR600 type cable to cut down on the
losses, especially at 50MHz and above. I am thinking of going with LMR600
right up to the antennas, making sure to oversize the rotor loop. I
successfully used solid center LMR400 for 10 years, so I might gamble this time
again. The loss figures for LMR400 keep pushing me that direction! Any idea
what size conduit I will need if I opt to run 9 runs of LMR600 size cable and
one rotor cable? I was able to easily get 10 LMR400 size cables in either 2 or
2.5" conduit (can't recall, as the last tower/qth was 10yrs
ago). I stopped at HD and looked at 3" conduit, but damn, that stuff just
looks too darn big, especially when it will be going into the side of my home.
I was planning on entering just above the concrete foundation, where there is
an approx. 8" sill between the concrete and where the first floor rests. Same
as the utilities do.
One other thing - my plan was to run the conduit from the house out to the base
of the tower, sink a few 4x4s into the ground near the tower base, then mount
some sort of grey weatherproof enclosure on them. Have the conduit from the
house go directly into the bottom of the box, then have another elbow come out
the bottom, allowing the coax cables to make a drip loop before they head up
the tower. Inside, I was planning to install a copper plate to which I would
affix 10 or so Polyphasor arrestors, and the rotor control surge arrestor.
Then bond the plate and tower to common ground rods near the tower. Can anyone
recommend a suitable enclosure that will comfortably fit 10 or so surge
arrestors, plus some room to spare. I took a quick look at the DX Eng website,
but their stuff only accomodates two or three devices.
I also need to install an electrical outlet near the base for the tower motor.
So I will be running a 3/4" conduit as well, from the main panel out to the
tower base. Any objection to dropping the electrical conduit in the same
trench as the coax conduit?
Finally, as far as grounding goes - is there any advantage to installing three
8ft ground rods at the bottom of the tower foundation hole BEFORE I pour the
concrete, and run the ground wires up thru the concrete base, to be attached to
the tower once it is erect? Or just stick to three ground rods into the dirt
around the base of the tower foundation after it is done?
Thanks for your insight and knowledge. I've been learning a lot just reading
the postings of the last month or two in preparation for this project.
Eric
K2WD
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