On Mon, 9 Feb 2009 15:30:50 -0600, "Howard Kowall"
wrote:

sorry I should mention the RG-59 is used for impedance matching not feed
line
thanks again
Howard

"Howard Kowall" wrote in message
...
Hello all
What determines the Velocity Factor of a coax cable.
Is it the center conductor awg,dielectric,shield or all combined
I am building a
Lindenblad Antenna for 2 Meters

its asked to use

RG-59 polyethylene foam coax with stranded center conductor

I think the VF is .66

I cant find any stranded center cond where I am,so I want to try it with
Solid,but it seems all the solid is VF .88

You might want to consider using RG-6/u instead of RG-59. These daze,
the quality of RG-59 coax is rather marginal. I've seen 80% coverage
shielding and cable unsuitable for outdoor use. Meanwhile, the CATV
people have switched to RG-6/u for everything. Much of it is quad
shielded and UV resistant. Velocity factor is usually 0.66 for solid
dielectric and anywhere between 0.7 and 0.9 for various foam
dielectric mixes. When you find a suitable piece of cable, grab the
manufacturer and full part number. Then, lookup the VF on the mfg
data sheet.


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
# http://www.LearnByDestroying.com AE6KS

You might want to consider using RG-6/u instead of RG-59. These daze,
the quality of RG-59 coax is rather marginal. I've seen 80% coverage


Beware of the Aluminum foil and shields though. Once it gets wet there is
no stopping the internal corrosion and will generate broadband noise under
power. This includes both RG6 and 9913 and LMR types. They have been
banned from all commercial sites around here.

Bring a knife with you and inspect before you buy. Tinned Copper braid is
better, Silver clad rigid is best.

On Tue, 10 Feb 2009 16:04:16 GMT, "JB" wrote:

You might want to consider using RG-6/u instead of RG-59. These daze,
the quality of RG-59 coax is rather marginal. I've seen 80% coverage

Beware of the Aluminum foil and shields though. Once it gets wet there is
no stopping the internal corrosion and will generate broadband noise under
power. This includes both RG6 and 9913 and LMR types. They have been
banned from all commercial sites around here.

Amazing. I can see it's possible to create a diode mixer junction
with electrolytic action between the aluminum foil and copper braid.
I've never seen broadband noise from coax cable. Usually the foil is
mylar or polyester coated and the copper is tinned or silver plated to
eliminate any points of contact. Most of the radio sites I've seen
are stuffed LMR-400 and LMR-600. Heliax is better, but also far more
expensive. Incidentally, if you want to generate RF noise and mixing,
there's nothing better than an abraided Heliax outer jacket, with the
copper shield touching the zinc galvanized tower.

If intermod were really a problem with foil shielded coax, then the
common residential CATV distribution system would have a big problem
with intermod and mixes. While the buried coax is semi-rigid with a
solid aluminum shield, the pole to house drops are usually quad
shielded RG-6/u (sometimes with a messenger wire) with foil and braid
shields.

Bring a knife with you and inspect before you buy. Tinned Copper braid is
better, Silver clad rigid is best.

Mylar or polyester coated aluminum foil is more important. Scrape the
insulation and see if it flakes loose from the foil. I've seen this
on very old 9913 and some new LMR-400 of dubious origin.

Slight change of topic.... do the commerical sties that ban foil
shielded coax also ban nickel plated connectors? Just curious.


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
# http://www.LearnByDestroying.com AE6KS

In article ,
Jeff Liebermann wrote:

Beware of the Aluminum foil and shields though. Once it gets wet there is
no stopping the internal corrosion and will generate broadband noise under
power. This includes both RG6 and 9913 and LMR types. They have been
banned from all commercial sites around here.

Amazing. I can see it's possible to create a diode mixer junction
with electrolytic action between the aluminum foil and copper braid.
I've never seen broadband noise from coax cable. Usually the foil is
mylar or polyester coated and the copper is tinned or silver plated to
eliminate any points of contact. Most of the radio sites I've seen
are stuffed LMR-400 and LMR-600. Heliax is better, but also far more
expensive. Incidentally, if you want to generate RF noise and mixing,
there's nothing better than an abraided Heliax outer jacket, with the
copper shield touching the zinc galvanized tower.

If intermod were really a problem with foil shielded coax, then the
common residential CATV distribution system would have a big problem
with intermod and mixes. While the buried coax is semi-rigid with a
solid aluminum shield, the pole to house drops are usually quad
shielded RG-6/u (sometimes with a messenger wire) with foil and braid
shields.

I don't think those cases (commercial/repeater and CATV) are
comparable.

As I understand it (anecdotal report and discussions with other
repeater owners/builders), the problem with LMR-400 and similar cables
occurs when the cable is used in a duplex application, with RF
transmit power and the incoming receive signal being carried on the
same cable simultaneously.

Under these conditions, it doesn't take very much broadband noise
generation at all (from the cable, connectors, or nearby
metal-on-metal contacts) to cause a problem. The transmitter might be
pumping 50 volts RMS of power into the cable, while the receiver is
trying to pick off a signal of less than a microvolt at a frequency
only 600 kHz away. That's a rather critical environment which really
can't tolerate more than a tiny percentage of noise generation in the
cables, connectors, or duplexer.

I don't think there's any problem with using these sorts of cables in
commercial or amateur service in *simplex* applications... they can
handle transmitting, or receiving, just fine. It's only when you try
to do both, simultaneously, through the same cable. that the noise
generation can become a problem.

The same can be true of some classes of antenna problems. The
repeater system I help maintain developed a serious desensitization
problem, due to internal corrosion/oxidation which occurred in the
antenna after several years up in the weather. I doubt that the
corrosion/oxidation effect would ever have been noticed if the antenna
were in service as a normal (simplex) base antenna - it didn't affect
the transmit SWR or the receive sensitivity at all,

I believe that CATV distribution is a rather easier situation for the
cable to handle, since the signals being carried are all of a fairly
similar and moderate power level. The downstream carrier levels
delivered to the home seem to be around 1 millivolt... that's more
than 60 dB higher than what a repeater's receiver has to be able to
pick out when it's receiving a just-usable signal from the outer edge
of its service area.

--
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!

"Dave Platt" wrote in message
...
In article ,
Jeff Liebermann wrote:

Beware of the Aluminum foil and shields though. Once it gets wet there
is
no stopping the internal corrosion and will generate broadband noise
under
power. This includes both RG6 and 9913 and LMR types. They have been
banned from all commercial sites around here.

Amazing. I can see it's possible to create a diode mixer junction
with electrolytic action between the aluminum foil and copper braid.
I've never seen broadband noise from coax cable. Usually the foil is
mylar or polyester coated and the copper is tinned or silver plated to
eliminate any points of contact. Most of the radio sites I've seen
are stuffed LMR-400 and LMR-600. Heliax is better, but also far more
expensive. Incidentally, if you want to generate RF noise and mixing,
there's nothing better than an abraided Heliax outer jacket, with the
copper shield touching the zinc galvanized tower.

If intermod were really a problem with foil shielded coax, then the
common residential CATV distribution system would have a big problem
with intermod and mixes. While the buried coax is semi-rigid with a
solid aluminum shield, the pole to house drops are usually quad
shielded RG-6/u (sometimes with a messenger wire) with foil and braid
shields.

I don't think those cases (commercial/repeater and CATV) are
comparable.

As I understand it (anecdotal report and discussions with other
repeater owners/builders), the problem with LMR-400 and similar cables
occurs when the cable is used in a duplex application, with RF
transmit power and the incoming receive signal being carried on the
same cable simultaneously.

Under these conditions, it doesn't take very much broadband noise
generation at all (from the cable, connectors, or nearby
metal-on-metal contacts) to cause a problem. The transmitter might be
pumping 50 volts RMS of power into the cable, while the receiver is
trying to pick off a signal of less than a microvolt at a frequency
only 600 kHz away. That's a rather critical environment which really
can't tolerate more than a tiny percentage of noise generation in the
cables, connectors, or duplexer.

I don't think there's any problem with using these sorts of cables in
commercial or amateur service in *simplex* applications... they can
handle transmitting, or receiving, just fine. It's only when you try
to do both, simultaneously, through the same cable. that the noise
generation can become a problem.

The same can be true of some classes of antenna problems. The
repeater system I help maintain developed a serious desensitization
problem, due to internal corrosion/oxidation which occurred in the
antenna after several years up in the weather. I doubt that the
corrosion/oxidation effect would ever have been noticed if the antenna
were in service as a normal (simplex) base antenna - it didn't affect
the transmit SWR or the receive sensitivity at all,

I believe that CATV distribution is a rather easier situation for the
cable to handle, since the signals being carried are all of a fairly
similar and moderate power level. The downstream carrier levels
delivered to the home seem to be around 1 millivolt... that's more
than 60 dB higher than what a repeater's receiver has to be able to
pick out when it's receiving a just-usable signal from the outer edge
of its service area.

You got it. Only hardline is authorized on the tower. Hardline doesn't
have the problem because it doesn't have a braid to flex in the wind. Braid
is less than satisfactory for RF Ground and lightning protection too.
Copper ribbons and sheets are preferred for grounds, but regular large
copper cable can be substituted in some cases. On a repeater system,
corroded or old braided coax hoses your own receiver and others nearby on
the tower or the next building with noise. Especially in the wind. You
won't hear that on simplex because the receiver is muted when you transmit.

I don't know if you have seen CATV hardline with a tank strapped to the
utility pole. That keeps water out by pressurizing the hardline. CATV
systems DO have problems with corrosion all the time. With all that cable
though, the cost to get it up and running is enormous, and they would rather
be complaint driven instead. They also use circulators so that the stuff
people do in their house doesn't feed back into the system and screw all the
other customers up.

The 2m people, most business PLMR and the Cops don't get it so they complain
about jammers so you get irate service calls. But you can't talk to them
because if you talk technical, they cover their ears, scream LALA LALA!!
accuse you of lying, and they won't pay for the cure anyway (remember, if
you have to think about the answer, you're lying). We do use LMR and 9913
for cheap simplex ground level base station installs because it is cheaper
and easier to route. Don't use it around your rotor though. The foil will
tear up.

JB wrote:

I don't know if you have seen CATV hardline with a tank strapped to the
utility pole. That keeps water out by pressurizing the hardline. CATV
systems DO have problems with corrosion all the time. With all that cable
though, the cost to get it up and running is enormous, and they would rather
be complaint driven instead. They also use circulators so that the stuff
people do in their house doesn't feed back into the system and screw all the
other customers up.

Ever open up a cable amp that has had leaky (water type leaky) coax
dripping into it? Yikes, they usually keep working for a while, with all
kinds of electrolyzing going on. It's a pretty sad sight.


- 73 de Mike N3LI -

"Michael Coslo" wrote in message
...
JB wrote:

I don't know if you have seen CATV hardline with a tank strapped to the
utility pole. That keeps water out by pressurizing the hardline. CATV
systems DO have problems with corrosion all the time. With all that
cable
though, the cost to get it up and running is enormous, and they would
rather
be complaint driven instead. They also use circulators so that the
stuff
people do in their house doesn't feed back into the system and screw all
the
other customers up.

Ever open up a cable amp that has had leaky (water type leaky) coax
dripping into it? Yikes, they usually keep working for a while, with all
kinds of electrolyzing going on. It's a pretty sad sight.


- 73 de Mike N3LI -

I've seen boxes of them. I wish I had pictures of the Micor mobile that was
parked in a supervisors car in the middle of a river for 3 days. The
battery went dead making green slime. The only money they had in the budget
was for repair, so we bid them to replace every board. The Mastr Exec had a
Relay and worked fine after drying it out. Things like that are hard to
explain.

In article ,
JB wrote:

I don't know if you have seen CATV hardline with a tank strapped to the
utility pole. That keeps water out by pressurizing the hardline.

Shameful. Just *imagine* the effect of all that nitrogen leaking out
into the atmosphere! What won't those cable guys try go get away with
next? (grin)

CATV
systems DO have problems with corrosion all the time. With all that cable
though, the cost to get it up and running is enormous, and they would rather
be complaint driven instead. They also use circulators so that the stuff
people do in their house doesn't feed back into the system and screw all the
other customers up.

The 2m people, most business PLMR and the Cops don't get it so they complain
about jammers so you get irate service calls. But you can't talk to them
because if you talk technical, they cover their ears, scream LALA LALA!!
accuse you of lying, and they won't pay for the cure anyway (remember, if
you have to think about the answer, you're lying).

Heh. You haven't met the senior hardware guy (Scott N6NXI) on our
2M/220/440 repeater project. He's the staunchest opponent of using
foil/braid cable on a repeater that you're ever likely to meet, and
insisted on all of our stuff being done to solid commercial-grade
standards (circulators, bandpass filters on the auxiliary radios,
etc.). Most of the cables inside the rack are custom-cut/routed .25"
heliax.

It was a lot of work (and more money) but it has paid off in
reliability. We've got 3 repeaters and their duplexers in a single
rack, right next to one another, and no crosstalk or intermod or
desense problems... and we share the site with a powerful
paging-service transmitter and a bunch of public-service radio gear.

We do use LMR and 9913
for cheap simplex ground level base station installs because it is cheaper
and easier to route. Don't use it around your rotor though. The foil will
tear up.

Good point - thanks - I'll remember to use a braid-cable jumper when I
put up a hexbeam later this year.

--
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!

The 2m people, most business PLMR and the Cops don't get it so they
complain
about jammers so you get irate service calls. But you can't talk to them
because if you talk technical, they cover their ears, scream LALA LALA!!
accuse you of lying, and they won't pay for the cure anyway (remember, if
you have to think about the answer, you're lying).

Heh. You haven't met the senior hardware guy (Scott N6NXI) on our
2M/220/440 repeater project. He's the staunchest opponent of using
foil/braid cable on a repeater that you're ever likely to meet, and
insisted on all of our stuff being done to solid commercial-grade
standards (circulators, bandpass filters on the auxiliary radios,
etc.). Most of the cables inside the rack are custom-cut/routed .25"
heliax.

It was a lot of work (and more money) but it has paid off in
reliability. We've got 3 repeaters and their duplexers in a single
rack, right next to one another, and no crosstalk or intermod or
desense problems... and we share the site with a powerful
paging-service transmitter and a bunch of public-service radio gear.

Say R56 and it usually covers everything that matters. Check this out. Use
to take care of a bunch of UHF Micors he

http://eecue.com/images_archive/eecu..._Antennas.html
(no i didn't take the picture)

"Dave Platt" wrote in message
...

snip

I don't think there's any problem with using these sorts of cables in
commercial or amateur service in *simplex* applications... they can
handle transmitting, or receiving, just fine. It's only when you try
to do both, simultaneously, through the same cable. that the noise
generation can become a problem.

The same can be true of some classes of antenna problems. The
repeater system I help maintain developed a serious desensitization
problem, due to internal corrosion/oxidation which occurred in the
antenna after several years up in the weather. I doubt that the
corrosion/oxidation effect would ever have been noticed if the antenna
were in service as a normal (simplex) base antenna - it didn't affect
the transmit SWR or the receive sensitivity at all,

All metallic contacts are potential problems. For years I did Navy
electronics, including a couple hundred EMI inspections. Where "topside
housekeeping" was neglected, broadband noise (BBN) was sure to be a problem.
(All topside metallic objects need to be either insulated or firmly
connected -- no incidental contact.)

As little as a hundred watts would excite some junctions to generate BBN
that could be detected throughout the HF band on other antennas. More power
would generate BBN up to several hundred MHz. Been there.