[TowerTalk] 90 degree coax bend atop a crankup tower

[ve4xt at mymts.net]

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 at 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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