Thank you gentlmen for your knowledgeable replies.
I suspected this might be more complicated than dig and bury, and
it can be given moisture, oxidation and ionic contamination by the
soil, or rodent activity.
I'll look for the DB suffix on coax, though I fear it might be something
that might be only found at hamfests, not Home Depot.
I got a 500' spool of RG-8 by Belden, but I wouldn't know it's
archival quality for years. I guess the manufacturer may or may not know
either, as the variables can be difficult to guage.
Thanks again

Les KA9GLW

Hello...
I'm planning to trench and bury RG-8 (or something similar) but don't know
if this will have adverse effects to the vinyl jacket.
Does anyone know if there's a better coax for this intent, or can it work
for 20 yrs.?
Thanks for any ideas.

Les

"les" wrote in message
...
Hello...
I'm planning to trench and bury RG-8 (or something similar) but don't know
if this will have adverse effects to the vinyl jacket.
Does anyone know if there's a better coax for this intent, or can it work
for 20 yrs.?
Thanks for any ideas.

Les

Figure about 8-10 years. Sun on the tower will deteriorate the jacket.

Moisture will be absorbed to some degree by the jacket and cause trouble.

Plasticizers in the jacket will bake into the center insulation and
contaminate. Copper, Aluminum, Tin compounds will also contaminate the
center insulation.

There is some advantage to running a 4" conduit, because it will allow you
to replace the coax and allow the best life by allowing drainage and
airspace.

Note that coax like 9913 and LMR cannot be allowed to get ANY moisture
inside the jacket or there will be corrosion throughout the cable leading to
broadband noise. If it is flexed around a rotor, the inside foil shield
will be broken and contaminated by the outer shield.

Cables like 8214, RG-8 without foil shields do better around rotors.

It will help to paint the cable.

Of course, carefully assemble all connectors and tape to keep moisture out.

Beware, some antennas will leak moisture right through the connector ruining
all your good work.

Hello...
I'm planning to trench and bury RG-8 (or something similar) but don't know
if this will have adverse effects to the vinyl jacket.
Does anyone know if there's a better coax for this intent, or can it work
for 20 yrs.?

"RG-8" is a designation that's both extremely generic, and technically
obsolete... this hasn't been a maintained military standard for a long
time. Cables which generally meet the common meaning of "RG-8" might
either do very well in a direct-burial application, or keel over and
die within a short period of time... the devil is in the details.

What you want, if you want to do this, is a specific type of cable
which is designated for "direct burial". These generally have a
couple of important physical characteristics:

- The outer insulating jacket is "non-contaminating". It tends to
resist the infiltration of water and other materials from the soil,
which can otherwise contaminate the dielectric inside the cable and
lead to high losses.

- It's often "flooded"... the interior of the braid/shield area is
flooded with a sticky semi-liquid. If the outer insulation is
damaged somehow (e.g. gopher-chew), the flooding material will
prevent moisture from wicking into the cable.

One specific variety of this sort of cable is LMR-400DB (the "DB"
being, of course, "direct burial"). I'm sure there are others.

As a counter-example, I wouldn't recommend using 9096, 9913 or any
other air-dielectric cable, unless you're willing to go to the trouble
of pressurizing it with dry nitrogen for the next 20 years :-)

I suppose that another option is to run a buried, waterproof conduit,
and then run coax through the conduit. I'm not sure that this would
work out any better than direct burial... keeping the conduit
leak-free, and free of condensation from atmospheric "breathing" is
difficult.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

les wrote:
Thank you gentlmen for your knowledgeable replies.
I suspected this might be more complicated than dig and bury, and
it can be given moisture, oxidation and ionic contamination by the
soil, or rodent activity.
I'll look for the DB suffix on coax, though I fear it might be something
that might be only found at hamfests, not Home Depot.
I got a 500' spool of RG-8 by Belden, but I wouldn't know it's
archival quality for years. I guess the manufacturer may or may not know
either, as the variables can be difficult to guage.
Thanks again

Les KA9GLW


Why not get the same cable the Cable Companies use?
I live in a rather wet country,(NL) and those cables
have been in the ground for more than 20 years here.

"Sjouke Burry" wrote in message
...
les wrote:
Thank you gentlmen for your knowledgeable replies.
I suspected this might be more complicated than dig and bury, and
it can be given moisture, oxidation and ionic contamination by the
soil, or rodent activity.
I'll look for the DB suffix on coax, though I fear it might be something
that might be only found at hamfests, not Home Depot.
I got a 500' spool of RG-8 by Belden, but I wouldn't know it's
archival quality for years. I guess the manufacturer may or may not know
either, as the variables can be difficult to guage.
Thanks again

Les KA9GLW


Why not get the same cable the Cable Companies use?
I live in a rather wet country,(NL) and those cables
have been in the ground for more than 20 years here.

Of course 7/8 hardline DB would last 20 years if nothing chewed it, but
will you live where you are for the next 20 years? Is it worth spending so
much more? Large conduit and less expensive coax is most cost effective and
allows expansion of the station. Unless you are really going to run more
than 100' then surplus TV hardline becomes attractive.

On May 13, 9:04*am, "JB" wrote:
"Sjouke Burry" wrote in message

...





les wrote:
Thank you gentlmen for your knowledgeable replies.
I suspected this might be more complicated than dig and bury, and
it can be given moisture, oxidation and ionic contamination by the
soil, or rodent activity.
I'll look for the DB suffix on coax, though I fear it might be something
that might be only found at hamfests, not Home Depot.
I got a 500' spool of RG-8 by Belden, but I wouldn't know it's
archival quality for years. I guess the manufacturer may or may not know
either, as the variables can be difficult to guage.
Thanks again

Les * * * * * *KA9GLW

Why not get the same cable the Cable Companies use?
I live in a rather wet country,(NL) and those cables
have been in the ground for more than 20 years here.

Of course 7/8 hardline DB *would last 20 years if nothing chewed it, but
will you live where you are for the next 20 years? *Is it worth spending so
much more? *Large conduit and less expensive coax is most cost effective and
allows expansion of the station. *Unless you are really going to run more
than 100' then surplus TV hardline becomes attractive.- Hide quoted text -

- Show quoted text -

yes, place the coax inside PVC drain pipe at the top of the tube, do
not lay it on the bottom. Arch the pipe slightly so that drainage is
out to the end(s) of the pipe. Place an access point at the end with
an inverted chamber. Think of the construction as though the whole
thing is under water, and any moisture that gets in has a path out,
construct it like that, and it will last longer than 20 years, and not
cost too much, just require some careful efforts.

Robert

On Tue, 12 May 2009 10:09:43 -0700, les wrote:

Thank you gentlmen for your knowledgeable replies. I suspected this might
be more complicated than dig and bury, and it can be given moisture,
oxidation and ionic contamination by the soil, or rodent activity.
I'll look for the DB suffix on coax, though I fear it might be something
that might be only found at hamfests, not Home Depot. I got a 500' spool
of RG-8 by Belden, but I wouldn't know it's archival quality for years. I
guess the manufacturer may or may not know either, as the variables can be
difficult to guage. Thanks again

Les KA9GLW

Les I did a bit of checking and found that coax for burial is called
wetted it contains a wetting agent in the pvc covering intended to keep
out moisture and protect the braid from water infiltration. I suspect it
probably has a silicon oil or other silicon compound intergrated.
If you do a search for this type you will find its is readily available
from many sources including lots of sattelite suppliers.

About the only type you would get from a hamfeast is heliax and I doubt
you want to keep a bottle of nitrogen hooked up to it all the time.

Gnack

Thank you gentlmen for your knowledgeable replies. I suspected this might
be more complicated than dig and bury, and it can be given moisture,
oxidation and ionic contamination by the soil, or rodent activity.
I'll look for the DB suffix on coax, though I fear it might be something
that might be only found at hamfests, not Home Depot.

A local Belden, or Times Microwave distributor might be your best bet.

Or, order it from http://www.therfc.com or a similar mail-order
distributor.

Belden seems to use the WB suffix to indicate flooded, water-resistant
cable, suitable for burial. 7810WB is a low-loss RG-8 type with those
characteristics.

I got a 500' spool
of RG-8 by Belden, but I wouldn't know it's archival quality for years. I
guess the manufacturer may or may not know either, as the variables can be
difficult to guage.

If it'd designed for direct burial, the manufacturer can almost
certainly tell you.

If it isn't, they may say "Son, you're on your own!"

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!