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Re: [TowerTalk] LMR degradation

To: towertalk@contesting.com
Subject: Re: [TowerTalk] LMR degradation
From: K8RI <K8RI-on-TowerTalk@tm.net>
Date: Wed, 27 Mar 2013 11:20:25 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
On 3/27/2013 10:06 AM, Patrick Greenlee wrote:

A large multi turn loop of LMR400 Or a conventional rotator loop of Davis BuryFlex(TM) works just fine and the jackets are plenty rugged You do sane two connectors... actually, a splice takes 6 two male and a double female on each end

You can put a female connector on each end of the rotator loop and save two connectors. They are available for UHF and N connectors.

Putting a snug piece of the corrugated plastic tube over the coax, but I'm a firm believer in keeping it simple. You don't want anything that might catch on something.


73

Roger (K8RI)
What about putting something over the rotation loop coax? How about the
corrugated black plastic wire loom covering?  Or better, maybe a cloth
cover made from sun resistant awning material.  Even I could sew up
something as simple as that, just one long seam.  Alternatively you
could just loosely wrap the cloth around the coax and secure with an
adhesive, maybe securing with string around it in several places to hold
it together while the adhesive is setting/curing.  Maybe contact cement
and no wait after putting it together. worried about longevity?  Put on
two or more independent layers. The second layer won't begin to degrade
from the UV until the first layer fails. Ditto the 2nd and 3rd.  Good
sun resistant awning material last for years in the sun and weather.

There is flexible corrugated looking spiral wrapped aluminum conduit
that flexes very easily, enough to handle the flexure required of a
properly constructed loop.  A bonus would be that the aluminum doesn't
transmit much UV through to the coax jacket.  The spiral wrap flexible
aluminum conduit is not water proof (don't get the type with the plastic
coating as it is much stiffer and will hold water.) The Flexible
aluminum conduit will drain and not retain water.

Comments?

P.S.  The 40 ft tall tower with 14 ft plus leg separation disassembly
project has been on hold while I assist an older ham get up an antenna
mast to get his antenna up almost 40 ft.  Also the series of sprinkles
and cold winds have been discouraging.  I did manage to make the trip to
the site twice, once to clear brush and 30 years growth of trees with
trunks and branches intertwined in the tower's X braces and a second
trip with a tractor to push the brush and downed trees out of the way so
I can get in with my trailers, tractor, and truck.  As promised, I'll
have pix when this project moves forward.  I have two other towers on
the ground waiting for bases and to be put up.  I am anxious to get my
hex beam up so I might install one of these before I take the BIG ONE down.

73

Patrick AF5CK

-----Original Message----- From: Cqtestk4xs@aol.com
Sent: Wednesday, March 27, 2013 7:57 AM
To: TOWERTALK@contesting.com
Subject: Re: [TowerTalk] LMR degradation

Like I said in my post I've been using regular LMR 400 for years on many
antennas.  Never had a failure if you leave a good sized loop.

Bill K4XS


In a message dated 3/27/2013 2:37:48 A.M. Coordinated Universal Time,
gary_mayfield@hotmail.com writes:

What are you supposed to put around the rotor  then?

73,
Joe kk0sd



From: Cqtestk4xs@aol.com
Date:  Tue, 26 Mar 2013 11:42:22 -0400
To: TOWERTALK@contesting.com
 Subject: Re: [TowerTalk] LMR degradation

Back in the early  2000s I had a long conversation with the guys at
Times.
The ultra  flex on many of my jumpers had cracked after only a couple of
years  in the FL sun. His response was the ultraflex was not supposed to
be
 used outside.

He offered to replace the stuff with regular  400 but I never took him up
on it.

I use the regular  LMR 400 on all my jumpers and have had zero problems.

Bill  K4XS


In a message dated 3/26/2013 1:25:47 P.M.  Coordinated Universal Time,
k8ri@rogerhalstead.com writes:

On 3/25/2013 2:31 AM, Jim Brown wrote:
> On 3/24/2013 9:42  PM, Jim Hoge wrote:
>> Today I discovered that I have had  environmental ingress beneath the
>> outer jacket of some ~8  year old LMR-400.
>
> In the latest (I think) version of  his excellent Managing Interstation
> Interference," W2VJN notes  that he observed degradation in the
measured
> performance of stubs  made of LMR400 that had been sitting in his
garage
> for a bit less  than a decade. He seemed to think it was due todegraded
> contact  between the foil and braid shields. This was written several
>  years ago. He may have more to say about it by now.

We've  known for years the UF versions of the LMR cables deteriorate out
in  the elements. It follows that they'd possibly do so with age as well.

I found that the braid had almost disentegrated in some pieces of
LMR400UF where the jacket "appeared" to syill be in good shape. I
thought perhaps the jacket had become porous, but perhaps not?I  wonder
which LMR400 he's talking about.

73

Roger (K8RI)


>
> 73, Jim  K9YC
> _______________________________________________
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>
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