AD5VJ Bob wrote:
First,
Congratulations!
> Hey guys *FINALLY* got my first tower since licensed 1965 in the air and it
> sure looks pretty standing tall and proud as I drive up
> to the QTH, I know this sounds strange, but I had to drive up to the house a
> couple of extra times just to look at it again Hi Hi
>
> Cant believe I am looking at mine and not someone else's Hi Hi
>
> Now I am looking for anyone who may have in excess to their needs some guy
> wire for the prettiest Rohn 25 tower in Texas. I have it
> up at 30 feet.
>
Fortunately the leverage of a tribander on a 30' tower isn't all that
bad. I'd check the strength, but I'd guess 3/16" galvanized wire rope
will be strong enough, but it varies in strength for source to source.
> I have already priced what else I need and after buying the concrete and all,
> retail pricing is more than I can do right now, so
> looking for a good deal from someone who has some laying around and is
> willing to part with it.
>
> 3/16 or 1/4 guy wire should be fine I am guessing.
>
You need to be as careful about over guying as under guying. Remember
the guy tension is supposed to be *about* 10% of the working strength
for that cable. The weight and tension of the cable both pull down on
the tower as well as out. With a 30 to 40 footer you have a lot of
leeway as to cable size and strength. I'd go to the ROHN site (do a
google search) and look up the guying for that particular tower.
They don't show a 30 footer in the catalog, but for 25G towers they use
3/16" and for a 40 footer footer they attach at the 38' level and anchor
it 32' out from the base.
> I am guessing to guy it at the 25 foot level I need a set of three at about
> 50 feet length each, if this is overkill please let me
>
You'd probably put the guys about 2 feet below the top and use an angle
between 40 and 60 degrees with the ground. But if you want to stick with
what ROHN does for the angle on a single level guy system just figure it
based on what they do with the 40 footer. You end up with a right
triangle, 38' tall and a 32' base. The length would be the square root
of the sum of the base length squared plus the height squared. IE.
SQR(38^2 + 32^2) I'll leave it up to you to figure the angles (remember
your high school Trig, if not let me know) with should be the same for
the shorter tower. Just the lengths would be different.
> know, I also need the associated hardware, brackets ect. I am not using the
> Rohn Guying bracket since a Ham told me I didn't need to
> spend that kind of money for a guy bracket, just tie it to the leg of the
> tower.
>
There are many ways this can be done. "Good enough" or good engineering
practice.
First, and I know there are many on here who will emphatically disagree,
but you can safely get away with things on a 30 or even 40 foot tower
that would be really dangerous on a 60 footer. Forces (and expense) go
up rapidly with height so any compromise made on a short tower should be
taken in light of how it's used and something that should never be tried
on taller towers. Never compromise with safety or safety equipment.
Falling from 30 feet can make you just as dead as falling from a hundred.
> The guy who will climb the tower (using his harness and his GinPole to mount
> the three element tribander) next weekend said he
> wanted me to use two cable clamps at each end of each guy wire, so I need 12
> of those.
>
>
With 3/16" I always use 3 and a wire thimble to attach to a bracket.
Although the ham is correct in that at 30 feet you can just wrap the
cable around the tower leg, but it is not a solid mechanical connection.
The tower leg can move inside the guy line and that will eventually wear
on the tower let, galvanizing, and the wire rope. Personally I'd not go
the extra money for either EHS cable or Phyllistran BUT if you do plan
on eventually using this for the base of a larger installation you need
to plan ahead and not cut any corners with any portion of the project.
I mentioned I have used dirt bases on some towers holding some fairly
good size antennas. On a guyed tower the purpose of the base is to hold
the tower in place while not sinking into the ground. Up here, I've seen
90 foot towers holding tri-banders using dirt bases. We have the soil
that will hold them in place. Sill my 45G sets in plenty of concrete.
That's getting a bit too large to depend on sand an clay from keeping it
held rigidly in place. OTOH I'd never recommend to any one they
specifically use a dirt base.
So good luck and welcome to the ranks.
73
Roger (K8RI - ARRL Life Member)
www.rogerhalstead.com
N833R (World's oldest Debonair)
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