My original answer was based only on the epoxy and using the proper
type, but...
On 5/5/2010 5:37 PM, RICHARD SOLOMON wrote:
> I am thinking about putting up a 4M Dish for EME. There is a rather large
> and thick Concrete Pad out back (the former owner had a large pigeon coop).
>
> I could use a section or two of Rohn 45 for the support, but what would I
> use as Guy Anchors in the Concrete Pad ? And what would I use to attach
> them to the pad.
>
The first question: How thick is that pad? "Rather large and thick" is
pretty vague.
A 4" pad as Mark mentioned, is not very strong structurally (6" is
better and 8" is better still while a foot sounds much better) and is
unlikely to have been high quality if it was poured as the floor for a
chicken coop. It is heavy, but I'd be wary of using it as the sole
means of guying a 4 meter dish. (13' diameter or 3.14159*6.5^2 = 134.8
ft sq.) which is a LOT of wind load. This is the equivalent of over 4 4'
X 8' sheets of plywood broadside to the wind. OR taken antenna wise it
is equivalent to OVER 14 KT36XA M^2 tribanders! Admittedly a mesh dish
would have a some what lesser load, and one made of tube like the old
Wineguard UHF dish, even less, but I'm going to assume you are not going
to stick with 144 MHz as the upper limit for EME and will be using
either a solid, or fine mesh dish.
Some years back, before Direct TV and DISH Net work, when C-Band was
near the peak of its popularity we had a rather strong wind storm. On
my way to work I noticed what was probably a 10' dish (most ranged fro 8
through 12') AND the slab of concrete on which it was mounted ( probably
10' X 10'). The whole works had tipped over. The concrete slab was
still in tact but standing on edge using the dish, which was on the
ground, for support.
The above was apparently with a slab poured to serve as an anchor as the
typical slab would have broken up.
Even if it's in a relatively protected area, I'd be more than a little
cautious. Maybe I'm being a bit overly cautious, but I'd at least bore a
hole through the center of the slab and pour a base for at least a 6" or
8" pipe and fill the pipe with concrete along with a few lengths of rerod.
73
Roger (K8RI)
> I read about some form of Concrete Epoxy, but if I recall that's the stuff
> that dropped a chunk of the Ted Williams Tunnel on some poor devil's car !!
>
> Thanks for any ideas,
>
> 73, Dick, W1KSZ
>
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