We have no favorite among the two coaxes, and the loss difference between
the two is miniscule, but it should be noted that the construction of the
core(centerconductor plus dielectric) in LMR 400 is the same as that of
the hardline in the query, and the mylar aluminum "sandwich" is bonded to
the foam in the final procedure of the fabrication of the coax. Thus the
oxygen contamination, if any, must come from the termination, where
technique is the governing agent. Both 9913 and LMR400, when chilled,
will have a significant partial vacuum - the former in the air spaced
core and the voids between strands in the braid, and the latter in only
the voids in the braid. Thus either coax can suck oxygen, water, or what
have you if the connector is sealed improperly. The hardline has only the
voids or bubbles in the foam, making it less at risk, but poor sealing at
the ends will still cause trouble through gas and vapor ingress.
The greater value in hardline comes with the completely impermeable solid
metal shield, protecting the "guts" of the cable itself for many years,
and the very low cost of maintenance after proper installation, so
important for commercial work.
The various models of flexible coax are the extension, where applicable,
of the hardline, none of which can handle a rotor traverse.
The main point of all of this remains - ALL of the installations require
hermetic sealing at the junctions and terminations - the chain is only as
strong as its weakest link.
We use what we can afford or scrounge - that's the hobby.
Press Jones, N8UG, The Wireman, Inc., Landrum, SC, 29356
Sales (800)727-WIRE(9473) or orders@thewireman.com
Tech help (864)895-4195 or n8ug@thewireman.com
www.thewireman.com and the WIRELINE bargain page
Our 21st year!
On Mon, 13 Jul 1998 13:42:39 +0100 Scott Bullock
<sales@advantagecomm.net> writes:
>
>While neither cable is as good as regular hardline, I pick the 9913
>over
>the lmr cable, it's been around longer, and is tried and true. Both
>cables
>will have a problem with oxygen contamination into the center
>insulation as
>they are not sealed, but i'd take 9913 for better longevity. I'm from
>the
>old school. Cut apart a piece of 9913 or lmr 20 years from now, and
>then do
>the same to a piece of hardline and you'll see what I mean. That
>discolored center insulation spells LOSS with a capital L. I see this
>type
>of thing in the commercial end every day.
>
>Scott
>KA1CLX
>
>
>At 10:07 AM 7/13/98 -0400, you wrote:
>>
>> All Right guys,
>>
>> What is the general consensus on 9913 vs LMR400? I have a 120 ft
>run
>> to my tower base. A 100 ft tower which will have a 3 tribander
>stack,
>> as well as a cushcraft 2 ele 40. I also have several hundred
>feet of
>> 7/8 black jacket CATV line(75 ohm). I have heard the connectors
>have
>> more loss than it's worth for the hardline. What are your
>> recommendations. I already have the 9913 and the LMR400!
>>
>>
>> 73 and Thanks
>>
>> Bill N4ZI Atoka, TN
>>
>>--
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>>
>>
>>
>
>--
>FAQ on WWW: http://www.contesting.com/towertalkfaq.html
>Submissions: towertalk@contesting.com
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>
>
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