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Outdoor flown electrical cable
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John Savage
science forum addict


Joined: 24 Mar 2005
Posts: 63

PostPosted: Fri Jul 14, 2006 4:08 am    Post subject: Re: Outdoor flown electrical cable Reply with quote

Bill Holt <bill@itsound.demon.co.uk> writes:
Quote:
I think flexing of the copper in the wind might not be the biggest
problem, as the outer PVC sheath is quite thick on these cables. We are
looking at cables with 8 individually screened quads - i.e. 4 insulated
wires laid in a diamond formation, screened with lap-wound copper,
aluminium foil or mesh copper (the first of these is preferred), then
insulated. The 8 of these are held within a fairly robust outer PVC
sheath. The question is really what to do about this outer sheath to
protect it from the sun, rain, wind and rodents.

I can't see where you've said what the distance to be spanned is? But
don't the telephone companies run their cables through extruded grey
poly pipe in your neck of the woods? You can see where these emerge
from the soil and lead up the side of the house. I'm sure the phone
company would not be using this material if all they'd be getting out
of them is a life of a decade or two. Here is Australia where the
sun's UV radiation is nothing short of *fierce* the pipe seems
indestructable, able to withstand all that is thrown at it except the
bumper of a reversing vehicle. It's lightweight and strong, very stiff,
and about the diameter of your thumb.
--
John Savage (my news address is not valid for email)
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N:dlzc D:aol T:com (dlzc)
science forum Guru


Joined: 25 Mar 2005
Posts: 2835

PostPosted: Wed Jul 12, 2006 2:19 am    Post subject: Re: Outdoor flown electrical cable Reply with quote

Dear Bill Holt:

"Bill Holt" <bill@itsound.demon.co.uk> wrote in message
news:PImrxFpUH2sEFwKh@itsound.demon.co.uk...
Quote:
In message <dhb6b2pt8iqqaofu1pn135t51me7a4v8rt@4ax.com>, Bob
bbx107.XYZ@excite.XYZ.com> writes
I think OP is from UK, so exposure to sunlight is not
a big problem.

(Do note however that such testing does not mean it
fails at 720 hr.)

And also note that 60 days << 10 years.

Quote:
But seriously... Your comments and Eric's seem
more authoritative than anything I have to say. I
guess I still wonder if the power folks, if not audio
folks, have something better to offer.

Thanks for all the replies. Yes, I'm from the UK,
but the sun does occasionally get through. Hadn't
thought of squirrels, but as the American grey
ones have eaten all our English red squirrels, they
might be a problem. I don't think we have too many
woodpeckers here either.

Yet. If you do get them: 1) I am sorry, and 2) it is not my
fault.

Quote:
I think flexing of the copper in the wind might not
be the biggest problem, as the outer PVC sheath
is quite thick on these cables.

The sheath will crack and fail in much less than 10 years. Now
you are depending on copper wiring exposed to the elements. How
tall are the two buildings where you are intending to run the
cabling, and how tall total are they?

Quote:
We are looking at cables with 8 individually
screened quads - i.e. 4 insulated wires laid in
a diamond formation, screened with lap-wound copper, aluminium
foil or mesh copper (the first of these is
preferred), then insulated. The 8 of these are held
within a fairly robust outer PVC sheath.

So it looks to me like a PLC running a deterministic network over
optical fiber, with 16 analog inputs, will be a perfect solution.
The fiber can be run usually up to 3 km, the data arrives always
on schedule. I'll name a brand if you are interested.

Quote:
The question is really what to do about this outer
sheath to protect it from the sun, rain, wind and
rodents.

Any such solution will require periodic maintenance. And do not
expose the wire insulation to the Sun (and the other crap the
real world brings).

Quote:
I have already been discussing the alternatives of
multiplexed audio, codecs etc., and running via an
alternative route on CAT-5 cable might be an option.
But that may involve latency (delay) issues in the
coding processes, and it is a much less versatile
answer than old-fashioned wires.

Hardly less versatile. Ethernet is not deterministic, other
architectures can be. If you have no other traffic, Ethernet
will be just fine. But do it over fiber, that way you have
automatic optical isolation.

Quote:
I am aware of precautions against lightning strikes,
and there are also checks to be made regarding
the phase of the power supplies and the earthing
(grounding) for the equipment at the two ends of
the run.

I would assume that the UK has the equivalent of the USA's
"National Electrical Code" (NEC), and that you have contacted an
electrical contractor. I also assume you will have contacted a
structural engineer regarding your catenary cabling, and what it
will do to the harmonics of your buildings (a couple of stories
probably not an issue, but if it was only a couple of stories,
why bother trying to go direct).

Eternal insulation *is* used in the power industry. It is huge
ceramic insulators that have to be manually cleaned occasionally,
and air. They don't bother to polymer-insulate the wires, since
such insulation always fails (and tends to hold moisture in the
cracks, speeding corrosion). They simply separate the conductors
with enough air to self-heal upon arc formation.

Anyway, good luck.

David A. Smith
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Bill Holt
science forum beginner


Joined: 03 Feb 2005
Posts: 5

PostPosted: Tue Jul 11, 2006 8:31 am    Post subject: Re: Outdoor flown electrical cable Reply with quote

In message <dhb6b2pt8iqqaofu1pn135t51me7a4v8rt@4ax.com>, Bob
<bbx107.XYZ@excite.XYZ.com> writes
Quote:
I think OP is from UK, so exposure to sunlight is not a big problem.

(Do note however that such testing does not mean it fails at 720 hr.)


But seriously... Your comments and Eric's seem more authoritative than
anything I have to say. I guess I still wonder if the power folks, if
not audio folks, have something better to offer.

Thanks for all the replies. Yes, I'm from the UK, but the sun does
occasionally get through. Hadn't thought of squirrels, but as the
American grey ones have eaten all our English red squirrels, they might
be a problem. I don't think we have too many woodpeckers here either.

I think flexing of the copper in the wind might not be the biggest
problem, as the outer PVC sheath is quite thick on these cables. We are
looking at cables with 8 individually screened quads - i.e. 4 insulated
wires laid in a diamond formation, screened with lap-wound copper,
aluminium foil or mesh copper (the first of these is preferred), then
insulated. The 8 of these are held within a fairly robust outer PVC
sheath. The question is really what to do about this outer sheath to
protect it from the sun, rain, wind and rodents.

I have already been discussing the alternatives of multiplexed audio,
codecs etc., and running via an alternative route on CAT-5 cable might
be an option. But that may involve latency (delay) issues in the coding
processes, and it is a much less versatile answer than old-fashioned
wires.

I am aware of precautions against lightning strikes, and there are also
checks to be made regarding the phase of the power supplies and the
earthing (grounding) for the equipment at the two ends of the run.

Thanks again.
--
Bill Holt
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Charles111
science forum beginner


Joined: 04 May 2006
Posts: 11

PostPosted: Tue Jul 11, 2006 6:09 am    Post subject: Re: Outdoor flown electrical cable Reply with quote

On Mon, 10 Jul 2006 20:02:46 +0100, Bill Holt
<bill@itsound.demon.co.uk> wrote:

Quote:
I'm new here, so this may be a stupid question or in the wrong group,
but can anyone help with the following.....

I'm an audio engineer and have been asked to advise on a suitable
specialised multi-pair cable that has to run between two buildings using
a catenary (sp?) supporting wire.

I've now talked to a leading supplier of such cable and they say that
none of their cables are suitable, quoting water vapour absorption and
the effects of UV etc. Most of their cables have an outer insulating
layer of PVC, although one or two are polyethylene.

I have experience of things like the reaction between polystyrene foam
and PVC, and also have a boat where the 'good quality' mains cable used
for masthead lights has become brittle and crumbly where it is exposed
to the elements.

So the question is... what is the best way to protect a cable of this
type? I've been thinking of some sort of paint or other coating, or
threading it through a length of layflat hosepipe. I'm not sure whether
the latter would survive the conditions or whether it might react with
the PVC.

I've asked elsewhere and other audio specialists have confirmed that
these cables are not considered suitable for permanent outside use, but
farmers seem to favour the 'just do it' approach.

Obviously weight is of the essence, and the cable will swing in the
breeze stressing the ends of the flown section. We are looking for a
minimum life of approx 10 years.

Any advice or suggestions would be very welcome.


Isn't this what the telephone companies have been doing for many
years?

I'd try calling a telephone equipment supplier, Graybar is one.
Unless there is something quite special about the signals you are
trying to carry, they should have what you need.
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Bob111
science forum Guru Wannabe


Joined: 13 Jan 2006
Posts: 115

PostPosted: Tue Jul 11, 2006 4:52 am    Post subject: Re: Outdoor flown electrical cable Reply with quote

On Mon, 10 Jul 2006 19:52:16 -0700, "N:dlzc D:aol T:com \(dlzc\)" <N:
dlzc1 D:cox T:net@nospam.com> wrote:

Quote:
Dear Bob:

"Bob" <bbx107.XYZ@excite.XYZ.com> wrote in message
news:i536b214glh52m2mdubjb92n5c07181q0e@4ax.com...
On Mon, 10 Jul 2006 20:02:46 +0100, Bill Holt
bill@itsound.demon.co.uk> wrote:

Hm, power (electricity) companies routinely use outdoor wiring,
for
much more demanding needs. And it lasts "a long time".

http://www.iaei.org/subscriber/magazine/00_f/ganatra.htm
"sunlight resistant" has to meet tests for a 720 hour period.
Such testing equates to only two months *if* the intensity is
"Sun average"...


I think OP is from UK, so exposure to sunlight is not a big problem.

(Do note however that such testing does not mean it fails at 720 hr.)


But seriously... Your comments and Eric's seem more authoritative than
anything I have to say. I guess I still wonder if the power folks, if
not audio folks, have something better to offer.


bob
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N:dlzc D:aol T:com (dlzc)
science forum Guru


Joined: 25 Mar 2005
Posts: 2835

PostPosted: Tue Jul 11, 2006 4:23 am    Post subject: Re: Outdoor flown electrical cable Reply with quote

Dear lucasea:

<lucasea@sbcglobal.net> wrote in message
news:x4Fsg.1948$2v.985@newssvr25.news.prodigy.net...
Quote:

"N:dlzc D:aol T:com (dlzc)" <N: dlzc1 D:cox T:net@nospam.com
wrote in message news:MgEsg.37549$AB3.28013@fed1read02...
I suppose it would be too expensive to us copper
pipe or copper tubing as the conduit.

Work hardening due to flexing. It will fail in time.

Hmm, I'm surprised, particularly with enough support
lines dropped from the catenary.

Wind. Tower sway. Woodpeckers.

Quote:
I would think it would be under very low stress, and
almost no strain. Still, you're right, SS might be
better. CS is clearly worthless, although paint
would help (but would have to be redone every few
years.)

Got just the guy...
http://www.pbs.org/wgbh/amex/newyork/peopleevents/p_petit.html

;>)

Quote:
Squirrels that run along one cable do just fine.
Squirrels that jump from one cable to another
do just fine. Squirrels that walk from one cable
to another get fried.

How about woodpeckers?

Dunno. Damn' things are too busy eating my
house to notice the wiring.

Need a remedy?

David A. Smith
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<lucasea@sbcglobal.net
science forum addict


Joined: 25 Mar 2006
Posts: 94

PostPosted: Tue Jul 11, 2006 3:44 am    Post subject: Re: Outdoor flown electrical cable Reply with quote

"N:dlzc D:aol T:com (dlzc)" <N: dlzc1 D:cox T:net@nospam.com> wrote in
message news:snEsg.37553$AB3.35899@fed1read02...
Quote:
Dear Bob:

"Bob" <bbx107.XYZ@excite.XYZ.com> wrote in message
news:i536b214glh52m2mdubjb92n5c07181q0e@4ax.com...
On Mon, 10 Jul 2006 20:02:46 +0100, Bill Holt
bill@itsound.demon.co.uk> wrote:

Hm, power (electricity) companies routinely use outdoor wiring, for
much more demanding needs. And it lasts "a long time".

http://www.iaei.org/subscriber/magazine/00_f/ganatra.htm
"sunlight resistant" has to meet tests for a 720 hour period. Such testing
equates to only two months *if* the intensity is "Sun average"... And is
intended for cable tray installation, definitely NOT flexure...

He's not going to get this with audio-grade cable, and weather will fry
any electronics at either end unless both towers get hit simultaneously
with lightning of equal intensity.

Good point. Opto isolators are probably a good idea, even if mux-demux and
fiber optic transmission aren't used.

Eric Lucas
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<lucasea@sbcglobal.net
science forum addict


Joined: 25 Mar 2006
Posts: 94

PostPosted: Tue Jul 11, 2006 3:40 am    Post subject: Re: Outdoor flown electrical cable Reply with quote

"N:dlzc D:aol T:com (dlzc)" <N: dlzc1 D:cox T:net@nospam.com> wrote in
message news:MgEsg.37549$AB3.28013@fed1read02...
Quote:
I suppose it would be too expensive to us copper
pipe or copper tubing as the conduit.

Work hardening due to flexing. It will fail in time.

Hmm, I'm surprised, particularly with enough support lines dropped from the
catenary. I would think it would be under very low stress, and almost no
strain. Still, you're right, SS might be better. CS is clearly worthless,
although paint would help (but would have to be redone every few years.)


Quote:
Squirrels that run along one cable do just fine.
Squirrels that jump from one cable to another
do just fine. Squirrels that walk from one cable
to another get fried.

How about woodpeckers?

Dunno. Damn' things are too busy eating my house to notice the wiring.


Quote:
If they ain't figured out how to insulate those
wires better than that, it's either not possible or
at least expensive and not commercially available.

I'd guess "not possible".

My point.

Cheers,
Eric Lucas
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N:dlzc D:aol T:com (dlzc)
science forum Guru


Joined: 25 Mar 2005
Posts: 2835

PostPosted: Tue Jul 11, 2006 2:52 am    Post subject: Re: Outdoor flown electrical cable Reply with quote

Dear Bob:

"Bob" <bbx107.XYZ@excite.XYZ.com> wrote in message
news:i536b214glh52m2mdubjb92n5c07181q0e@4ax.com...
Quote:
On Mon, 10 Jul 2006 20:02:46 +0100, Bill Holt
bill@itsound.demon.co.uk> wrote:

Hm, power (electricity) companies routinely use outdoor wiring,
for
much more demanding needs. And it lasts "a long time".

http://www.iaei.org/subscriber/magazine/00_f/ganatra.htm
"sunlight resistant" has to meet tests for a 720 hour period.
Such testing equates to only two months *if* the intensity is
"Sun average"... And is intended for cable tray installation,
definitely NOT flexure...

He's not going to get this with audio-grade cable, and weather
will fry any electronics at either end unless both towers get hit
simultaneously with lightning of equal intensity.

David A. Smith
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N:dlzc D:aol T:com (dlzc)
science forum Guru


Joined: 25 Mar 2005
Posts: 2835

PostPosted: Tue Jul 11, 2006 2:45 am    Post subject: Re: Outdoor flown electrical cable Reply with quote

Dear lucasea:

<lucasea@sbcglobal.net> wrote in message
news:qGDsg.46878$VE1.32799@newssvr14.news.prodigy.com...
Quote:

"N:dlzc D:aol T:com (dlzc)" <N: dlzc1 D:cox T:net@nospam.com
wrote in message news:uNBsg.37544$AB3.25131@fed1read02...
....
3) convert the signals to digital, multiplex (MUX)
them together, broadcast them with light,
DEMUX them, and convert back to analog. (MUX-DEMUX was later
shortened to MoDem)

No, MoDem is modulator/demodulator.

You are correct. There is a "muldem"!

Quote:
Nothing is multiplexed (at least before DSL)--
otherwise you'd've been able to make calls while
you surfed with your 28.8. All it did was the
digital-to-audio conversion (modulate) and back. I believe
communication protocols were talk-and-
answer, so no need for multiplexing crossing
signals. With DSL, I'm not sure if signals cross,
but at least the data is multiplexed with voice
(and of course signals from different phone lines
are multiplexed in that big green box in your neighborhood, but
that's done with voice-only
signals too, regardless of data.)

Still, the MUX idea is a good one, or a water pipe
as a conduit. PVC, c-PVC or polybutylene water
piping might be OK, especially if supported by a catenary.
Make it watertight the same way you
make water pipes watertight--by using solvent
glue to glue the sections together with couplings.

Why not use steel piping? Steel *has* a fatigue strength, is
water tight, and convey sound quite well.

Quote:
I suppose even those plastics will have a limited
sunlight lifetime.

Yes, between visible, UV and airborne contaminants (inclusive of
the woodpecker that worked through my cable TV cable because it
was in his way), no plastic will last "10 years" without
maintenance.

Quote:
I suppose it would be too expensive to us copper
pipe or copper tubing as the conduit.

Work hardening due to flexing. It will fail in time.

Quote:
Still support with a catenary, and make the couplings with
standard compression fittings.
Ground both ends has the advantage of excellent
rejection of RF interference, for what that's worth.

Probably not, since the two conductors are separated by large
distances, and could be free to have independent
positions/oscillations.

Quote:
Another way to look at insulation meant to
withstand the elements.... Think about the one
type of cabling that was installed with the
specific intention of withstanding the elements:
above-ground residential power/phone/TV cabling. Now go out
to your nearest power
pole and take a close look at that insulation on
the wires. If it's like most, it will be all cracked, and in
many cases, completely missing.
Squirrels that run along one cable do just fine.
Squirrels that jump from one cable to another
do just fine. Squirrels that walk from one cable
to another get fried.

How about woodpeckers?

Quote:
If they ain't figured out how to insulate those
wires better than that, it's either not possible or
at least expensive and not commercially available.

I'd guess "not possible".

David A. Smith
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Bob111
science forum Guru Wannabe


Joined: 13 Jan 2006
Posts: 115

PostPosted: Tue Jul 11, 2006 2:30 am    Post subject: Re: Outdoor flown electrical cable Reply with quote

On Mon, 10 Jul 2006 20:02:46 +0100, Bill Holt
<bill@itsound.demon.co.uk> wrote:

Quote:
I'm new here, so this may be a stupid question or in the wrong group,
but can anyone help with the following.....

I'm an audio engineer and have been asked to advise on a suitable
specialised multi-pair cable that has to run between two buildings using
a catenary (sp?) supporting wire.

I've now talked to a leading supplier of such cable and they say that
none of their cables are suitable, quoting water vapour absorption and
the effects of UV etc. Most of their cables have an outer insulating
layer of PVC, although one or two are polyethylene.


Hm, power (electricity) companies routinely use outdoor wiring, for
much more demanding needs. And it lasts "a long time".

Perhaps you could contact your local power company, or even an
electrician, for advice on proper type of outdoor wiring. Or maybe a
company that supplies cabling for electrical use. (I'm not suggesting
they will have what you want, but they should be helpful at explaining
the issues.)

bob
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<lucasea@sbcglobal.net
science forum addict


Joined: 25 Mar 2006
Posts: 94

PostPosted: Tue Jul 11, 2006 2:04 am    Post subject: Re: Outdoor flown electrical cable Reply with quote

"N:dlzc D:aol T:com (dlzc)" <N: dlzc1 D:cox T:net@nospam.com> wrote in
message news:uNBsg.37544$AB3.25131@fed1read02...
Quote:
Dear Bill Holt:

"Bill Holt" <bill@itsound.demon.co.uk> wrote in message
news:B3GY+lkWRqsEFwJ9@itsound.demon.co.uk...
I'm new here, so this may be a stupid question or
in the wrong group, but can anyone help with the
following.....

I'm an audio engineer and have been asked to
advise on a suitable specialised multi-pair cable
that has to run between two buildings using a catenary (sp?) supporting
wire.

Spelling correct.

Options
1) run the cable underground,
2) run the cable inside a flexible "liquidtite" conduit,
3) convert the signals to digital, multiplex (MUX) them together,
broadcast them with light, DEMUX them, and convert back to analog.
(MUX-DEMUX was later shortened to MoDem)

No, MoDem is modulator/demodulator. Nothing is multiplexed (at least before
DSL)--otherwise you'd've been able to make calls while you surfed with your
28.8. All it did was the digital-to-audio conversion (modulate) and back.
I believe communication protocols were talk-and-answer, so no need for
multiplexing crossing signals. With DSL, I'm not sure if signals cross, but
at least the data is multiplexed with voice (and of course signals from
different phone lines are multiplexed in that big green box in your
neighborhood, but that's done with voice-only signals too, regardless of
data.)

Still, the MUX idea is a good one, or a water pipe as a conduit. PVC, c-PVC
or polybutylene water piping might be OK, especially if supported by a
catenary. Make it watertight the same way you make water pipes
watertight--by using solvent glue to glue the sections together with
couplings. I suppose even those plastics will have a limited sunlight
lifetime. I suppose it would be too expensive to us copper pipe or copper
tubing as the conduit. Still support with a catenary, and make the
couplings with standard compression fittings. Ground both ends has the
advantage of excellent rejection of RF interference, for what that's worth.

Another way to look at insulation meant to withstand the elements.... Think
about the one type of cabling that was installed with the specific intention
of withstanding the elements: above-ground residential power/phone/TV
cabling. Now go out to your nearest power pole and take a close look at
that insulation on the wires. If it's like most, it will be all cracked,
and in many cases, completely missing. Squirrels that run along one cable
do just fine. Squirrels that jump from one cable to another do just fine.
Squirrels that walk from one cable to another get fried. If they ain't
figured out how to insulate those wires better than that, it's either not
possible or at least expensive and not commercially available.

Eric Lucas
Back to top
N:dlzc D:aol T:com (dlzc)
science forum Guru


Joined: 25 Mar 2005
Posts: 2835

PostPosted: Mon Jul 10, 2006 11:55 pm    Post subject: Re: Outdoor flown electrical cable Reply with quote

Dear Bill Holt:

"Bill Holt" <bill@itsound.demon.co.uk> wrote in message
news:B3GY+lkWRqsEFwJ9@itsound.demon.co.uk...
Quote:
I'm new here, so this may be a stupid question or
in the wrong group, but can anyone help with the
following.....

I'm an audio engineer and have been asked to
advise on a suitable specialised multi-pair cable
that has to run between two buildings using a catenary (sp?)
supporting wire.

Spelling correct.

Options
1) run the cable underground,
2) run the cable inside a flexible "liquidtite" conduit,
3) convert the signals to digital, multiplex (MUX) them together,
broadcast them with light, DEMUX them, and convert back to
analog. (MUX-DEMUX was later shortened to MoDem)

No flexible insulator will give eternal (> 1 year) performance.
I have painted coax that has been OK under paint for several
years, but no flexing. Additionally, copper has no fatigue
strength, so each "flex cycle" work hardens it, increases its
resistance, and brings it closer to being an "open".

Good luck.

David A. Smith
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Bill Holt
science forum beginner


Joined: 03 Feb 2005
Posts: 5

PostPosted: Mon Jul 10, 2006 7:02 pm    Post subject: Outdoor flown electrical cable Reply with quote

I'm new here, so this may be a stupid question or in the wrong group,
but can anyone help with the following.....

I'm an audio engineer and have been asked to advise on a suitable
specialised multi-pair cable that has to run between two buildings using
a catenary (sp?) supporting wire.

I've now talked to a leading supplier of such cable and they say that
none of their cables are suitable, quoting water vapour absorption and
the effects of UV etc. Most of their cables have an outer insulating
layer of PVC, although one or two are polyethylene.

I have experience of things like the reaction between polystyrene foam
and PVC, and also have a boat where the 'good quality' mains cable used
for masthead lights has become brittle and crumbly where it is exposed
to the elements.

So the question is... what is the best way to protect a cable of this
type? I've been thinking of some sort of paint or other coating, or
threading it through a length of layflat hosepipe. I'm not sure whether
the latter would survive the conditions or whether it might react with
the PVC.

I've asked elsewhere and other audio specialists have confirmed that
these cables are not considered suitable for permanent outside use, but
farmers seem to favour the 'just do it' approach.

Obviously weight is of the essence, and the cable will swing in the
breeze stressing the ends of the flown section. We are looking for a
minimum life of approx 10 years.

Any advice or suggestions would be very welcome.
--
Bill Holt
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