In a message dated 26/09/99 23:25:53 EST, frosty@kc1.net writes:
> I am in the process of putting up about 75 feet of Rohn 25G and have
> gotten some great answers here, but I still have several questions to
> straighten out my mine. I will
> have two sets of guys, one at 70 ft and the other at 35 feet. The first
> guys will be about
> 91 ft long, which I plan to break up into lengths of 4', 27', 27', 27',
> 11'; will this be ok??
Probably. The reason you break up the guys with insulators (or use
Phillystran) is to minimize/eliminate antenna interaction with the guys. If
you turn your beam and the SWR changes as it rotates - you've got interaction
problems. It's like you've got another parasitic element near the antenna
affecting the SWR and pattern.
There are lengths (I think 27' is one of them) that don't resonate
anywhere in the ham bands. A chart is listed (I think) in the ARRL Handbook
(sorry, I'm out of town and don't have my copy to check). If you just have a
triband beam, then all you really care about is 10-15-20. OTOH if you've got
wire antennas hung from the tower, you probably don't want them interacting
with the guys either.
> The other guys will be about 69 ft long, be broken up to 4', 27', 27',
> 6'; will this be ok??
Same as above.
> The other question I have comes from my earlier questions, all of the
> answers about using crosby clamps, suggested using grips, how do they
> install?? are there special tools??
They are Preformed Guy Grips and are available from ham tower dealers;
i.e. Texas Towers, etc. Go to their website and check them out.
They are installed by hand - no tools, special or otherwise - are
required. They're just MUCH easier and convenient to install than cable
clamps so feel free to use them if you like. Same comment on installing them
correctly (saddle on live side of cable).
Cheers, Steve K7LXC
Tower Tech
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