My first experience with non bonded foil on CATV cables was in the late 70's
when RG-59 type foam was widely used. Bad stuff.
In the mid 80's I was in charge of a commercial data, video, and voice
instalation over cable at an island refinery off Singapore.
The refinery hired a local cable installer who either didnt read the specs
or thought he could use cheap stuff and charge for the best ran all non
bonded cable. When I and the rest of the factory team arrived we quickly
discovered this and made the contractor completely redo it.
A similar experience was a year later when the USN hired a Norfolk area
union contractor to cable the USS Carl Vinson, CVN-70 with quad shield
RG-11. The network was having almost constant errors and local techs were
stymied.By that time I was in R&D management for the cable group and my boss
elected me to go lead the team since it was rather political and the s**t
was hitting the fan as the ship was scheduled to get underway for its
shakedown cruise in a few days.
It didnt take long to discover that standard copper braid RG-11 foam was
used and you could even see external radio and TV stations on the spectrum
analyzer and when the ships transmitters were activated they took out huge
chunks of spectrum. Their armored coax cables were running parallel and
sometimes touching the RG-11.
I got an enjoyable 2 week sea cruise out of that ending in being catapulted
off the flight deck off the coast of Cuba.
Carl
KM1H
Carl
KM1H
----- Original Message -----
From: "Bill Wichers" <billw@waveform.net>
To: "Tom W8JI" <w8ji@w8ji.com>; <topband@contesting.com>
Sent: Friday, June 22, 2012 2:32 PM
Subject: Re: Topband: Coax for Beverages
>> The inner foil should be bonded directly to the dielectric surrounding
> the
>> center conductor. Otherwise, the cable will have an outdoor life
> issue. I
>> can't recall the last cable I saw without the innermost foil bonded to
> the
>> dielectric. I suppose someone somewhere makes bad cable that will wick
>> water
>> or trap moisture in that critical area. Normal reasonable quality
> cable
>> has
>> a bonded foil, meaning the foil is bonded directly to the center
>> dielectric.
>
> There is some non-bonded foil cable out there. I don't like it as it's
> much more difficult to properly terminate. Much of the bonded cable also
> has a backer on the foil though -- if you remove the foil on that type
> there is commonly a blue film on the "back" of the foil. It might be a
> remnant of the adhesive, I'm not sure about that. My point was that even
> if there is a plastic film on the foil, it would be on the side of the
> foil that isn't in contact with the braid anyway.
>
>> There is a triaxial cable that has a layer of insulation between
> shields,
>> sometimes Mylar, but that is outside the innermost shields.
>
> Sounds a bit like RT-142 that has a separator between the braided
> shields.
>
>> As hard as we look for something wrong with CATV cables, there is very
>> little to find wrong. Other than susceptibility to very low frequency
>> energy, which doesn't bother us unless lightning opens the foil, it is
>> great
>> stuff.
>
> Personally, I've even used fully non-flooded "regular" CMR-type RG6
> cabling direct buried with no problems for 15+ years. I would *not*
> recommend that (I was in a hurry way back then and didn't have the
> correct cable), but it can work. I prefer the polyethylene-jacketed
> flooded RG6 for outdoor use. It can also be easily found in orange which
> makes it easier to find when digging holes, but note that the orange
> jacket doesn't hold up nearly as well in sunlight as the black jacket.
>
> It's also possible to get RG6 with a solid copper (BC) center conductor
> instead of the more common copper clad steel (CCS) center conductor. You
> need to get the RG6 types for security (CCTV) systems, or for
> direct-broadcast satellite systems. Both of those tend to have the BC
> center conductor for either the low-frequency composite video (for
> security cameras) or DC power for the LNB (for satellite). Cost is
> higher and availability lower for those cable types, unfortunately.
>
> -Bill
> _______________________________________________
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