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Triaxial cable, what for? - RF Cafe Forums
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Lipari
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Post subject: Triaxial cable, what for?
Posted: Mon Feb 23, 2009 1:27 pm
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Joined: Mon Feb 23, 2009
1:06 pm Posts: 1 |
Hi everyone, I'm working on a project involving
antenna installations on a navy ship. The specifications
call for using triaxial antenna cable, i.e. coaxial
cable with two separate AND insulated shields.
I've done a lot of antenna installations in
many sorts of environments and normally I use double
braided cable like RG-214 or foil+braid cable. This
normally satisfies all requirements for shielding
as foil+braid cable has a shielding efficiency of
around -90dB. I've been searching the internet
for more knowledge, and I've found some manufacturers
like Times that makes triaxial cable and others
like Trompeter and King that makes connectors.
The cable specs are not so impressive, they
seem to be equivalent to the foil and braid double
shielded coax. The pricing is however very impressive
.
Also the connectors look very expensive.
So what are the true benefits of using triax
for HF and VHF shipborne antennas? Has it got something
to do with EMP protection levels? I would
appreciate any input on this from someone more knowledgeable
then I.
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nubbage |
Post subject: Re: Triaxial cable, what for?
Posted: Sat Feb 28, 2009 5:00 am
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General |
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Joined: Fri Feb 17, 2006
12:07 pm Posts: 236 Location: London UK
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Hi Lipari we often use double-screened coaxials
in the oil/gas industry on off-shore platforms,
in the sense that a regular RG-214 with a braid-armouring
jacket around the PVC outer sheath of the regular
RG-214 is pretty well what you describe. There
are 3 reasons this is done 1. for additional
mechanical strength in a tough outdoor environment
2. Differential grounding: the armouring is grounded
to any steelwork, while the inner breaid is grounded
to a low-noise low resistance earth to the bottom
of the vessel and the sea. 3. It affords better
lightning strike protection as the armouring can
be grounded outside a steel room, passed through
a wall transit with just the regular coax (having
stripped the armouring away) then the cable terminates
at the equipment end as usual.
_________________ At bottom, life is all
about Sucking in and blowing out.
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Posted 11/12/2012
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