PROBLEM

I have to hang a straight ~120 foot = 40 meter drop of RG-6 type
foamed dielectric coax. No way to secure it mid-way as it's an
abandoned and unaccessible chimney flue line.

Right now all the weight is on a rounded rest on top, diameter ~ 4"/10
cm, made by sticking 3 rubber pipes of different size one inside the
other and taping the coax to itself, leaning on a section of plastic
pipe

The weight is quite ~ 5 kg if I remember correctly. I think there is
no way that leaning over a 10 cm. dia. rest won't crush the foam
dielectric over the years. I may be wrong, but finding out is not
simple at all.

This thing now only carries HF and a bit of crushing is not important
(+ I can't easily test it!), but I want to make sure I can do 2 GHz in
the future, and I don't know the proper or standard way of hanging a
LONG vertical coax drop.

Now I have a chance to re-hang the coax, and I want to run it along a
load-bearing PVC-covered steel cable, perhaps 4 mm dia.. The coax
itself is the usual 6 mm -something. I am considering a couple of
options:

1) Three more loops, to have a support loop every 10m or so.
The cable drops from the top loop, then after 10m gently bends back
upward, then forward again over an arched support, taped to itself,
and continues the drop.

2) Many many nylon straps all along the drop.
I lay coax and steel cables horizontally. Keep the steel cable taught,
leave the coax loose, and gently tie a tiny nylon strap every meter or
so, barely to the point it holds 1 meter's weight, taking care not to
strangle the coax.

Suggestions? Comments?

On Nov 5, 2:50*am, spamhog wrote:
PROBLEM

I have to hang a straight ~120 foot = 40 meter drop of RG-6 type
foamed dielectric coax. No way to secure it mid-way as it's an
abandoned and unaccessible chimney flue line.

Right now all the weight is on a rounded rest on top, diameter ~ 4"/10
cm, made by sticking 3 rubber pipes of different size one inside the
other and taping the coax to itself, leaning on a section of plastic
pipe

The weight is quite ~ 5 kg if I remember correctly. I think there is
no way that leaning over a 10 cm. dia. *rest won't crush the foam
dielectric over the years. I may be wrong, but finding out is not
simple at all.

This thing now only carries HF and a bit of crushing is not important
(+ I can't easily test it!), but I want to make sure I can do 2 GHz in
the future, and I don't know the proper or standard way of hanging a
LONG vertical coax drop.

Now I have a chance to re-hang the coax, and I want to run it along a
load-bearing PVC-covered steel cable, perhaps 4 mm dia.. *The coax
itself is the usual 6 mm -something. I am considering a couple of
options:

1) Three more *loops, to have a support loop every 10m or so.
The cable drops from the top loop, then after 10m gently bends back
upward, then forward again over an arched support, taped to itself,
and continues the drop.

2) Many many nylon straps all along the drop.
I lay coax and steel cables horizontally. Keep the steel cable taught,
leave the coax loose, and gently tie a tiny nylon strap every meter or
so, barely to the point it holds 1 meter's weight, taking care not to
strangle the coax.

Suggestions? *Comments?

A suggestion.
When the cable TV guys ran the distribution line past our house a few
years ago they spiral wrapped stainless steel wire around the coax and
a messenger cable. The coax was the regular pvc type, not the solid
aluminum outer cover. It seems to have held up at least 10years.

They used a traveling spool carrier to spin the wire around the pair,
but could be done by hand by a couple of people.

As an alternative, you could buy a bunch of plastic tape and wrap the
coax+messenger tightly with at least two layers of tape. That would
give continuous support to the coax. A double wrap would probably
survive the elements better than a single wrap. Or you could get
several bottles of "liquid tape" and coat a single wrap of tape with
that.

Paul, KD7HB

I think what you are doing has potential 'problems', but you know
that. More support for that cable is certainly a good idea. The
'how' of it is one of those practical thingys, just depends on what's -
practical- for you.
I think you'll also find that RG-6 probably works okay on HF and VHF.
Get any higher in frequency and depending on the length of the run,
you can forget about using any of the 'common', non-hard line feed
lines. Get ready for that.
Either of the methods of supporting that feed line sounds like they'd
work. Pick whatever is easiest for you. And there ain't no 'perfect'
way of doing anything...
Paul

Thank you all!

@K1TTT
Yes, that's the technically idea solution, but I am trying to use
common materials that cost perhaps 5x less around here.

@'Doc
You have a point. I wrote RG-6-"type". There's a ton of various cables
types that are sold commercially as "similar" to RG-6. I referred to
the sat-tv cable that everybody uses around here, and you find it in
every electrical supplies shop. This cable is designed for use at
about 2GHz, which is the IF at which signals are sent down from the
LNB to the receiver.
- solid copper center conductor
- foamed PE dielectric
- 100% AL first shield, perhaps .1mm foil
- probably 60% AL second shield, stranded
- insulation 3kV DC test, in practice not a problem (if you don't
crush/melt the foam :-)
- emphatically NOT rated for power, tested and perfect up to 50W QRP
and RX, theoretically could take 1kW if well matched and not overheat
(see specs, do the math) but I never tried and ever will, I'd guess
will take 100W OK. I should do a high-current DC test perhaps.
- pain in the rearend to mate the AL to anything, must be pressure-
only, must be silicon grease coated on penalty or corrosion, but after
all this is how perhaps 300 million sat-TV systems work at 2GHz.
- loss 2dB/100m (m not ft) @ 10MHz, not bad
- ...75 ohm, but I either make my own impedances, or not care, or use
tuners, and 75 is OK for many applications.

@KD7HB
Plastic tape is probably the simplest and best, perhaps without even
wrapping the whole length - at a 30deg. angle spiral wrap I would need
240ft of tape! :-P. Also, tape is much gentler than sttap in terms of
pressure per unit of surface. Dish installers never use nylon straps
outdoors, just several turns of black, weather resistant PVC tape, and
it lasts at least 5-10 years. In my case, the drop is all inside a
flue line, well protected. Maybe I should use a large rope just for
wider surface. I'll do an overload test and see.

But another post around her tells me that perhaps there's a was to
test the line at 2GHz...

Thanks again to all.

On Nov 6, 10:08*am, spamhog wrote:
Thank you all!

@K1TTT
Yes, that's the technically idea solution, but I am trying to use
common materials that cost perhaps 5x less around here.

@'Doc
You have a point. I wrote RG-6-"type". There's a ton of various cables
types that are sold commercially as "similar" to RG-6. I referred to
the sat-tv cable that everybody uses around here, and you find it in
every electrical supplies shop. This cable is designed for use at
about 2GHz, which is the IF at which signals are sent down from the
LNB to the receiver.
- solid copper center conductor
- foamed PE dielectric
- 100% AL first shield, perhaps .1mm foil
- probably 60% AL second shield, stranded
- insulation 3kV DC test, in practice not a problem (if you don't
crush/melt the foam :-)
- emphatically NOT rated for power, tested and perfect up to 50W QRP
and RX, theoretically could take 1kW if well matched and not overheat
(see specs, do the math) but I never tried and ever will, I'd guess
will take 100W OK. I should do a high-current DC test perhaps.
- pain in the rearend to mate the AL to anything, must be pressure-
only, must be silicon grease coated on penalty or corrosion, but after
all this is how perhaps 300 million sat-TV systems work at 2GHz.
- loss 2dB/100m (m not ft) @ 10MHz, not bad
- ...75 ohm, but I either make my own impedances, or not care, or use
tuners, and 75 is OK for many applications.

@KD7HB
Plastic tape is probably the simplest and best, perhaps without even
wrapping the whole length - at a 30deg. angle spiral wrap I would need
240ft of tape! :-P. Also, tape is much gentler than sttap in terms of
pressure per unit of surface. *Dish installers never use nylon straps
outdoors, just several turns of black, weather resistant PVC tape, and
it lasts at least 5-10 years. *In my case, the drop is all inside a
flue line, well protected. Maybe I should use a large rope just for
wider surface. *I'll do an overload test and see.

But another post around her tells me that perhaps there's a was to
test the line at 2GHz...

Thanks again to all.

rg6 or 11 with steel messenger may be common depending on the local
cable tv practices. it is often used for running drops from the pole
to the house by catv installers.

rope would work in place of the cable, but pick a non-stretchy one.
polypropylene would be my first choice since it will be out of the
weather. and yes, only a couple turns of tape every 3 or 4 feet
should be plenty. and since it is enclosed you may not even need to
go all the way down, just enough to get to where you aren't afraid of
the weight of what is left stretching it any more.

spamhog wrote:
PROBLEM

I have to hang a straight ~120 foot = 40 meter drop of RG-6 type
foamed dielectric coax. No way to secure it mid-way as it's an
abandoned and unaccessible chimney flue line.

Right now all the weight is on a rounded rest on top, diameter ~ 4"/10
cm, made by sticking 3 rubber pipes of different size one inside the
other and taping the coax to itself, leaning on a section of plastic
pipe

The weight is quite ~ 5 kg if I remember correctly. I think there is
no way that leaning over a 10 cm. dia. rest won't crush the foam
dielectric over the years. I may be wrong, but finding out is not
simple at all.

This thing now only carries HF and a bit of crushing is not important
(+ I can't easily test it!), but I want to make sure I can do 2 GHz in
the future, and I don't know the proper or standard way of hanging a
LONG vertical coax drop.

Now I have a chance to re-hang the coax, and I want to run it along a
load-bearing PVC-covered steel cable, perhaps 4 mm dia.. The coax
itself is the usual 6 mm -something. I am considering a couple of
options:


Maybe you have the coax and steel cable for free, but ...

why not use the coax used for cable tv service drops which has the coax
and steel cable integrated into one assembly? It's got the jacket
integrated with the supporting cable, so the loads are very evenly
distributed, etc.

Thank you K1TTT and Jim.

I am not going to swap the whole line for a self-supporting type with
steel wire in it. I have plenty of spare coax at the low end to cut
out the potentially crushed bit and just shift it up.

K1TTT: yes, you correctly point out that the goal is to avoid undue
stress, and the last several yards can be left hanging.
Iterating back, the simplest trick of all will be to
- pull it up much of the way
- tape it to the steel rope in at least 3-4 points by taping them
together for at least a couple of feet
- let the span between two tiepoints hang somewhat loose.

Thanks again!