I have been using Belden 9913 RG-8U solid core for the past 7 years.
Its used with a Jogunn 5+5 beam and Yaesu rotor. Will this stand up for
another 10+ years or ditch it for some low loss, stranded, foam or
non-contaminating coax?

In , jim wrote:

I have been using Belden 9913 RG-8U solid core for the past 7 years.
Its used with a Jogunn 5+5 beam and Yaesu rotor. Will this stand up for
another 10+ years or ditch it for some low loss, stranded, foam or
non-contaminating coax?


Used coax can be tested on the bench for characteristic impedance, dielectric
integrity, DC resistance, and even for pinholes in the outer insulation. But
unless you measured these factors when new, you can't make a good determination
of its quality after several years of use. The problem is that your average coax
isn't hermetically sealed, so moisture will eventually seep in and slowly
corrode the conductors. Weaknesses in the outer insulation (due to age, oil
contamination, mechanical stresses and manufacturing imperfections) cause
microscopic pinholes that make the corrosion process go faster. It's best to
replace your coax periodically. I would say that seven years is plenty long
enough for an outside line.

Now I can't stress this enough: -=DON'T USE FOAM=-!!! There are several reasons
not to use foam. First, foam coax is very porous and is intended for controlled
environments where there is little variation in temperature and humidity, the
factors primarily responsible for moisture seeping into the coax. Second, the
dielectric softens with just mild heat, and the line could be ruined by nothing
more than a hot sunny day. Also, the foam doesn't have the mechanical strength
to handle the stresses of being clamped to an antenna and hung from any decent
height, not to mention the repeated movements caused by wind, or the expansion
and contraction caused by wide temperature changes. For antenna installations,
foam coax is -BAD NEWS-!

As far as solid vs. stranded is concerned, the only real advantage of solid is a
higher usable frequency (we're talking GHz here). Stranded conductors offer more
flexibility, which is important when the coax is constantly under the mechanical
stresses of an antenna installation.

The only other thing you may want to know about any type of coax is how flexible
it will be when the weather turns cold. In that respect, I have yet to find any
coax that fills the bill.







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"Frank Gilliland" wrote in message
...
In , jim wrote:

I have been using Belden 9913 RG-8U solid core for the past 7 years.
Its used with a Jogunn 5+5 beam and Yaesu rotor. Will this stand up for
another 10+ years or ditch it for some low loss, stranded, foam or
non-contaminating coax?


Used coax can be tested on the bench for characteristic impedance,
dielectric
integrity, DC resistance, and even for pinholes in the outer insulation.
But
unless you measured these factors when new, you can't make a good
determination
of its quality after several years of use. The problem is that your
average coax
isn't hermetically sealed, so moisture will eventually seep in and slowly
corrode the conductors. Weaknesses in the outer insulation (due to age,
oil
contamination, mechanical stresses and manufacturing imperfections) cause
microscopic pinholes that make the corrosion process go faster. It's best
to
replace your coax periodically. I would say that seven years is plenty
long
enough for an outside line.

Now I can't stress this enough: -=DON'T USE FOAM=-!!! There are several
reasons
not to use foam. First, foam coax is very porous and is intended for
controlled
environments where there is little variation in temperature and humidity,
the
factors primarily responsible for moisture seeping into the coax. Second,
the
dielectric softens with just mild heat, and the line could be ruined by
nothing
more than a hot sunny day. Also, the foam doesn't have the mechanical
strength
to handle the stresses of being clamped to an antenna and hung from any
decent
height, not to mention the repeated movements caused by wind, or the
expansion
and contraction caused by wide temperature changes. For antenna
installations,
foam coax is -BAD NEWS-!

As far as solid vs. stranded is concerned, the only real advantage of
solid is a
higher usable frequency (we're talking GHz here). Stranded conductors
offer more
flexibility, which is important when the coax is constantly under the
mechanical
stresses of an antenna installation.

The only other thing you may want to know about any type of coax is how
flexible
it will be when the weather turns cold. In that respect, I have yet to
find any
coax that fills the bill.







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Excellent answer! My only addition is (and correct me if I'm wrong)
electrons follow the surface of the wire and stranded wire offers more
surface area than solid wire.

--
visit http://www.geocities.com/linearschematics/

"Dr. Death" wrote in message
...
snip
Excellent answer! My only addition is (and correct me if I'm wrong)
electrons follow the surface of the wire and stranded wire offers more
surface area than solid wire.


At 11-meter frequencies it doesn't matter if you use stranded or solid
unless you are going hundreds of feet. Stranded coax is a bit more flexible
and forgiving of kinks. When you get into the UHF and microwave frequencies
then you should use coax with a solid center conductor, as Frank said.

Here's a tip that helps me with the cold weather problem of coax that needs
to flex. Use your high quality coax for the long run from your rig to the
base of your antenna, I use LMR-400. Run a short piece of RG-8x from the
base of the rotor to the connection on your antenna. You will need to
replace it every few years but it's cheep and a length of 10 or so feet
isn't going to give you much, if any measurable loss on 11-meters.

Kevin, WB5RUE




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In , "Kevin Muenzler, WB5RUE"
wrote:


"Dr. Death" wrote in message
...
snip
Excellent answer! My only addition is (and correct me if I'm wrong)
electrons follow the surface of the wire and stranded wire offers more
surface area than solid wire.


At 11-meter frequencies it doesn't matter if you use stranded or solid
unless you are going hundreds of feet. Stranded coax is a bit more flexible
and forgiving of kinks. When you get into the UHF and microwave frequencies
then you should use coax with a solid center conductor, as Frank said.


Bingo.


Here's a tip that helps me with the cold weather problem of coax that needs
to flex. Use your high quality coax for the long run from your rig to the
base of your antenna, I use LMR-400. Run a short piece of RG-8x from the
base of the rotor to the connection on your antenna. You will need to
replace it every few years but it's cheep and a length of 10 or so feet
isn't going to give you much, if any measurable loss on 11-meters.


Good idea. It also provides a convenient break in the run to install a grounding
block.






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"Frank Gilliland" wrote in message
...
In , "Kevin Muenzler, WB5RUE"

wrote:

Here's a tip that helps me with the cold weather problem of coax that
needs
to flex. Use your high quality coax for the long run from your rig to
the
base of your antenna, I use LMR-400. Run a short piece of RG-8x from the
base of the rotor to the connection on your antenna. You will need to
replace it every few years but it's cheep and a length of 10 or so feet
isn't going to give you much, if any measurable loss on 11-meters.


Good idea. It also provides a convenient break in the run to install a
grounding
block.


Actually if you install a grounding block and lightning hits you replace
your coax, your antenna and a grounding block. They don't do squat. Most
antennas are at DC ground anyway so ground your entire system not just the
coax. Of course if you are using a dipole you should be using a BALUN and
most come with a ground connection. DON'T expect it to save your radio in
the event of a direct (or close) strike. You are looking at hundreds of
millions of volts at hundreds of thousands of amps. That little grounding
block is going to vaporize along with your coax. If you want real
protection visit poliphaser. They have excellent stuff (at more than
"excellent" prices). Don't buy the $20 grounding blocks and expect
protection.

Kevin, WB5RUE




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"jim" wrote in message
...
I have been using Belden 9913 RG-8U solid core for the past 7 years.
Its used with a Jogunn 5+5 beam and Yaesu rotor. Will this stand up for
another 10+ years or ditch it for some low loss, stranded, foam or
non-contaminating coax?


Hi Jim Carroll, nice to hear from you!
I have always just replaced my coax every 8
to 10 years no matter what. I figure between
the use of millions of watts, wind, rain, ice, heat,
birds, low flying planes, it should just be replaced
for the old age aspect.

Landshark


--
Treat people as if they were what
they ought to be and you will help
them become what they are capable
of becoming.