Hi All,
I'm working on a grant application for a network expansion and I could use
some advice on the towers.
Our ground out here is either sandy, solid rock, soil (farm ground) or soil
and rock mix (also farm ground :-P).
I'll want the ability to put a distribution omni near the top (basically no
wind load), 3 sector antennas roughly 8" by 6" by 2'. Around half way we'll
want to run backhaul antennas (don't need to go to the top because we'll
have the towers no more than 15 miles apart). The backhaul antennas will be
3 3' dish antennas and 3 2' dish antennas per tower. There will also be the
radio units themselves and those boxes are about 1'x1'x4" on average. So
there will be from 6 to 15 of them per tower.
>From talking to my rep at Hutton it looks like there are two pretty good
choices for me. Both free standing towers and mono poles.
The free standing towers would make it easier to add things like ham
repeaters, public safety systems etc.
The mono poles are nearly half the money. I don't know what the cost of
mounting accessories would add though.
I do NOT want to use guyed towers if I can help it. No matter what I always
seem to end up with a link that has to shoot through the guy wires. grrr
We're in a 70mph wind zone here, though I've seen it hit 100 in the last few
years. No tornadoes etc. though.
What would you guys use? What factors affect your decision making process?
And FYI, the motor home emergency communications project is coming along,
slowly but it's moving. We did use it to provide free internet to people at
a couple of motorbike races about a month ago. I learned that 3 group 27
batteries take a LONG time to re-charge once they've been pulled completely
down. And they go down at a surprisingly high rate when you leave the
furnace on in a 29' motorhome! Using the DC charging port on a Honda 1kw
generator only give you 8 amps of charge. But the 4kw (built in and much
noisier!) unit will charge at 45 amps! Even with BOTH running it takes the
better part of 4 hours to bring the batteries full up to speed.
I've decided to install a 3' x 16" x 3" weather tight box on top of the
motorhome. I'll run a conduit from the cupboard that the radios will be in
to the box on the top. That will allow us to easily make changes to the
antennas without having much to worry about when it comes to water getting
into the coach. It'll also leave the inside looking as un cluttered as
possible and that'll be a good thing for momma!
The mast I built onto the coach (mostly for my backhaul high speed data
antennas) turned out to be pretty easy. I built a couple of brackets that
attached to the back of the coach (lag screwed into the solid wood
framework). They have u-bolts welded on and are painted body color so they
don't look bad at all. I then used a mix of galvanized EMT, fence pipe and
aluminized exhaust pipe. I welded nuts to the largest pipe (two of them, 6"
apart), I made a couple of t-handled bolts to fit the nuts. The middle pipe
and the top pipe are able to be pinned (with captive spring pins like you'd
use on a trailer hitch to keep the couple from rattling loose) at pre set
heights. I painted two bands on the inside pipes so that I could tell when
I was about out of room to push them up.
All pipes fit with almost no clearance, just enough to slide them up easily.
The inside most pipe is 2" o.d. so everything is strong enough that I don't
have to guy it, even with 2' grid antennas (two of them) on it. I didn't
put the system all of the way up this time, and I didn't have both antennas
at the very top. But we did have 40ish mph winds and there was NO sign of
anything loosening up and no damage to anything at all. I can take this
system up to nearly 30' above the ground and it still collapses small enough
that I can store it underneath if I choose to! If it's left on the coach
there are NO tools needed to raise and lower the mast and it can be turned
360* once it's up to the height that I want it at.
At some point I may drill some holes in the second pipe so that I can raise
it then pin it before tightening the t-handled bolts. This would make it
quite a bit easier to aim the antennas when needed, now I have to hold
everything up and turn, then tighten. I may also add a brace from the
bottom bracket to the bumper so that I can confidently stand on the upper
bracket while working on things. I don't think I've even got $100 into the
mast so far!
laters,
marlon
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