This is forwarded from the AR902Mhz mailing list. See the very bottom paragraph
about building the rebar cage. Somehow, I always thought that the rebar cage in
a concrete tower foundation was NOT to be welded together, just tied with some
kind of wire ties. Did I miss something along the way?
LJ
-----Forwarded Message-----
>From: Mike Morris <wa6ilq@pacbell.net>
>Sent: Dec 27, 2005 2:33 PM
>To: AR902Mhz@yahoogroups.com
>Subject: Re: [AR902Mhz] Tower Installation
>
>At 11:39 PM 12/26/05, you wrote:
>>(big chunk cut out)
>>Architectural Improvement form so I can submit my "project"...to install
>>a 30 foot Rohn tower for my 900 mhz antenna system and other antennas
>>related to repeater/remotebase and other link systems [a.k.a, antenna
>>farm on a tower].
>
>30 feet won't get you much above a normal house roof level.
>I'd plan on a 60 or even 90 foot tower and dig the base for that. You can
>always put a 30 foot tower on a base designed for 90... and add sections
>later.
>
>>My question on a typical tower installation and please keep in mind...I
>>have no experience in this area other then as a "helper" with other
>>installations years ago.
>>
>>Can someone direct me to a website or specifically explain how best to
>>"lay the foundation" to install a 30 foot Rohn tower without guy wires.
>
><http://members.aol.com/kj6y> or kj6y at aol dot com .....
>Skip has done over a hundred towers across the country and
>is well known among the DX community...
>might want to drop him an email and ask his opinion...
>
>Also if I remember correctly Rich WA8DBW used to have a
>web page about a tower re-installation at his place after an ice
>storm brought it down... used to be at
><http://pages.sssnet.com/richardr>... might want to drop him
>a line and ask what he'd do differently if he had to do it over...
>
>>Yes, I plan, once I purchase the tower sections [working on that with a
>>local Ham] to secure the second bottom section to the eave of the house.
>>In short, I think I want to sink/install the first five foot section of
>>the tower into the ground,
>
>The tower manufacturers have a base section that is designed for
>embedding into the concrete. It has thicker galvanizing and the top
>is designed to sit a few inches above the concrete, and have the
>real bottom section bolted to it. Or you can put a hinge plate
>between the two so you can tilt over the tower.
>
>>use rebar for added support and firmness,
>>pour cement to "fill the hole" at the base of a five foot section of the
>>tower, then secure the upper section to the eave of the house with steel
>>brackets [that I may have to have formed and bent to the right config].
>
>Please do what a friend of mine did not do... spend an extra half hour
>with a trowel on the wet concrete and make very sure that the concrete
>"peaks" under the bottom plate, so that rain water and melting snow
>runs AWAY from the tower legs poking through the concrete. He ended
>up with a low spot under the tower base and has an ongoing problem
>with puddles ... he expects to have a shorter tower life as a result of the
>water collection.
>
>>I am new at this so any and all suggestions on/from this list would be
>>appreciated so very much.
>
>Have a plastic conduit of 2.5" or larger going from the tower base into
>the house for feedlines and control lines. Have a 3/4" conduit for
>AC power at the base, and put a double wide weatherproof box on the
>end of the conduit. Run #10 or #12 wire in it, with two circuits (i.e. both
>sides of the 220) and run it through a labeled cutoff switch. If you
>ever get interested in HF you can put a crank up tower with a winch
>on the base. Lay an extra conduit or two - PVC pipe is cheap and you
>don't want to be in the position of saying "I could put the TV antenna
>up another 20 feet if I hand an extra conduit to get it into the house..."
>
>A year or so ago I helped a friend in Pasadena pour a patio in his back
>yard. He ran a water line to a faucet and a gas line for a BBQ, and
>several extra conduits and pipes under the concrete "just because he
>could". Come January 1 (i.e. Rose Parade) I was over at his place
>and his dad's Class A motor home was parked next to the patio...
>(his folks live in the SF Bay area) and I saw what the extras were
>for... one was a sewer line, one was telephone and cable TV, one
>was...
>
>Point is that schedule 40 PVC is cheap... just use sweeps
>instead of elbows.
>
>>This will be my new 900 mhz repeater and
>>remotebase project for 2006!! The wife and I have been living in our
>>new home now 15 months and I really desire to install a quality antenna
>>system for the three repeaters I currently operate and maintain.
>
>Sooner or later you will get interested in HF... my first exposure was
>backwards from most... in the late 70s a local guy had a UHF repeater,
>and two HF remote bases on it. He had a Heathkit monobander parked
>on 7255 WCARS net on 40m, and a Collins S-line parked on
>14.2<something> ... he could select any of four channels on 6m, eight
>channels on 2m, or the Heath, or the Collins all via touchtone. The
>Heath and Collins used the guy wires of the tower as inverted V antennas
>(the angle and length of the guys had been selected precisely
>for that purpose).... the 40M antenna ran north and south, the 20M
>ran east and west.
>I'm mentioning this only because I'm reading your posting as
>being interested in 900 and UHF only right now, and your interests
>may expand or change in the future. A larger tower base now is not
>that much more, and you may want to add HF in the future - maybe
>as a stand-alone station to start with, or maybe as a remote base
>off the 900MHz repeater. Might be fun to work the south pole
>direct instead of via IRLP.
>
>>So please comment/send thoughts and suggestions on your own experiences
>>with tower installatons. I am looking forward to "getting my hands
>>dirty", digging the hole for the tower and rebar and pouring the
>>cement...and at age 62, I NEED the exercise!!
>
>Another mistake that a friend made, but in a building as
>opposed to a tower base. For the purposes of avoiding
>RF rectification you always want to weld, not tie-wire the
>rebars to each other as you build the cage. When he built
>the concrete block building that is now a workshop behind
>his house he tie-wired the rebar. It rusted before the
>concrete was poured (some folks leave the blocks empty,
>he filled the blocks). He has iron oxide diodes every foot or
>so inside the walls. Some local codes forbid welding the
>rebar, some don't mention it. I don't know the reasons for
>not welding it.
>
>Mike WA6ILQ
>
>
>
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