[TowerTalk] LMR degradation

Wed Mar 27 11:20:25 EDT 2013

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 at aol.com
> Sent: Wednesday, March 27, 2013 7:57 AM
> To: TOWERTALK at 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 at hotmail.com writes:
>
> What are you supposed to put around the rotor  then?
>
> 73,
> Joe kk0sd
>
>
>
>> From: Cqtestk4xs at aol.com
>> Date:  Tue, 26 Mar 2013 11:42:22 -0400
>> To: TOWERTALK at 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 at 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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