On 9/9/2012 8:18 PM, Jim Lux wrote:
On 9/9/12 5:08 PM, Rick Kiessig wrote:
How do you figure out how much coax and control cable to put between your
rotator and the antenna?
The short answer is enough to reach, plus the rotator loop.
How do you secure those cables on both the tower side and at the antenna?
On regular towers I just use tape to form a band 2 to 3 inches wide
What kind of coax do you use there? BuryFlex or something else?
It depends on what you use for your regular coax. If it's a flexible
RG-8 I just use more of the same. That way I don't need to add more
connectors. I also use tape to hold the coax under the boom from the
tower to the feed point.
I do not like cable ties used on coax. They are narrow and can exert a
lot of pressure on the cable which may distort said cable.
I'm also looking for a good way to secure cables to the outside of the
tower. I'm not using a Rohn-style with multiple smaller support posts.
Instead, it's a single pole, 220mm in diameter. I'm reluctant to just use
long plastic cable ties. Is there a better approach?
That's roughly 8 1/2 inches
They make "stick on" things that look like the saddles you use with zip
ties to hold cables on a chassis, but made of metal or UV resistant
plastic with a bit of curvature.
To attach those, they have double stick foam (3M VHB - Very High Bond, I
think) that is very weather resistant (used for holding windows in on
skyscrapers, for instance). I have a 15-20 year old roll of VHB and
lots of things stuck up outside for more than 5 years that are still
stuck (in Southern California, so we don't get freezing very often, but
it does get hot.. surface temp in the sun is probably well over 60C)
I've seen metal surfaces way up here in Michigan reach over 100C laying
out in the sun. I believe a flat, protected surface of the proper
color can reach well above 300F
There are things which can be epoxied on, as well. Epoxy will never
come off, if the surface is properly prepared.
Typical epoxies that most of us use or that you find in the hardware
section will soften and fail in some areas. There is a reason that most
small composite aircraft are white. Park one that is green, black, or
red out in the sun and you will be able to see the rib and stringer
outlines through the skin in a few hours.
Check the temperature range for any specific epoxy. I use Vinylester
Resin which has a notably higher softening point and much lower
viscosity allowing for a much denser weave in the fiberglass cloth.
Unfortunately it has a relatively short shelf life once promoted
(Factory says 3 months, but typically less than a year. Much less if not
kept cool). Cure time is only about 15 to 20 minutes depending on how
much catalyst you use, how much promoter was originally used and the
working temp. Working and cure times are highly variable. Plus the
stuff is expensive at over $80 a gallon and requires hazmat shipping as
the catalyst is Methyl Ethyl Keytone Peroxide
On a pole I'd be tempted to fasten on the same kind of cable hangers
they use on crank up towers. Can't remember the name of them though.
73 and good luck
Roger (K8RI)
73, Rick ZL2HAM
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