Holding the coax in the sling "below" the bend makes sense, but the
vertical load on the center conductor is still there. That's why too
sharp a bend, or too gradual a bend are still problematic and long,
unbroken vertical runs still cause problems. The best all around
connectors are the 7-16 DIN.
73
Roger (K8RI)
On 6/5/2015 7:32 AM, ve4xt@mymts.net wrote:
Wouldn't holding the coax with a sling-type grip in such a way that the bend
itself is a tension-free loop, solve both problems?
The issue in both cases is the unsupported weight of the coax pulling on the
bend, yes? So if you took all the weight off the bend...
Or am I missing something?
73, Kelly
ve4xt
Sent from my iPad
On Jun 5, 2015, at 12:15 AM, "Roger (K8RI) on TT" <K8RI-on-TowerTalk@tm.net>
wrote:
Coax has two bend radius listed. A repeatable radius and a one time bend. It's a
good idea to stay well away from both of these. The one time bend can be a very
short radius. Short enough that the center conductor will want to migrate off center
given enough time just laying on a flat surface. The repeatable bend radius is
usually quite a bit larger and "should not damage the coax over a given number
of bends. No, I don't know the number, but the minimum repeatable bend radius can
still stress the coax.
Now hang a load on the coax in a vertical run. The center conductor will tend
to migrate downward. In a 100 ft vertical run it's often enough for N type
connectors to lose continuity. If the coax is supported only from the top
with a relatively sharp bend, the center conductor will migrate off center.
That's why several small loops evenly spaced up the side of the tower will
remove the load from that top support.
There are several methods of supporting the coax from the top on crank up
towers. Wire mesh and rope slings do a good job of holding the coax, but do
nothing for the linear migration of the center conductor. Several commercial
ones linked to on here appear to do a pretty good job,
Too sharp a bend causes the off center migration, while too wide a bend will allow the
linear migration. There has to be "a best radius" for each size and type of
coax. I'd choose about twice the repeatable bend radius. No concrete proof, it just
looks right. Not exactly a scientific approach.
Tall, crank up towers put a lot of stress on the coax supported only from the
top. Unfortunately supporting the coax at intermediate heights brings a whole
new can of worms.
73
Roger (K8RI)
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73
Roger (K8RI)
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