Coaxial Cable considerations for HF
 

Having re-entered ham radio after a 30 year hiatus, I would like to ask
about RG/8U versus other cable types for use in a simple dipole or G5RV
installation with 100W max. transmitter output. In the "good old days"
Low loss "8U" was sort of the standard. There are some newer cable
designations now.

Is there a better "standard" cable for the above use than RG/8U
(specifically Belden 9913 low loss)?

John
AB8O

Coaxial Cable considerations for HF
 

"jawod" wrote in message
...
Having re-entered ham radio after a 30 year hiatus, I would like to ask
about RG/8U versus other cable types for use in a simple dipole or G5RV
installation with 100W max. transmitter output. In the "good old days"
Low loss "8U" was sort of the standard. There are some newer cable
designations now.

Is there a better "standard" cable for the above use than RG/8U
(specifically Belden 9913 low loss)?

John
AB8O

For feeding a G5RV if the feedline is not much over 100 feet almost any coax
is good enough. Probably would not use the rg-58 , but would use rg-8X or
any of the rg-8 type coax. Would not waste the money on anything beter as
you would only gain a couple of tenths of a db if that much.

The 9913 is hollow inside and may be hard to keep the water out of. I had
some up for about 10 years and used it on 2 meters for ssb. It never did
get any wate rin it for me. I don't like the LMR 400 as the center
conductor is copper coated aluminum. Nothing wrong with that when it is
installed correctly, but I just do not like it. Davis makes some Burry Flex
that is very good, but over kill for the dipole. I just installed 4 beams
using about 500 feet of it, triband for 20,15,10, a 432 mhz, 144 mhz and a 6
meter beam. Would not have used it on the triband but wanted to just buy
one type of coax for the job.

Think I would use the rg-8X for the g5rv. I am feeding an 80 meter dipole
and also an off center fed dipole with the rg-8x running about 700 watts out
of a Heathkit sb200 amp.

Coaxial Cable considerations for HF
 

jawod wrote in news:68ca4$46182214$d066b697$10313
@FUSE.NET:

Having re-entered ham radio after a 30 year hiatus, I would like to ask
about RG/8U versus other cable types for use in a simple dipole or G5RV
installation with 100W max. transmitter output. In the "good old
days"
Low loss "8U" was sort of the standard. There are some newer cable
designations now.

Is there a better "standard" cable for the above use than RG/8U
(specifically Belden 9913 low loss)?

My article at http://www.vk1od.net/G5RV/index.htm models the efficiency
of a number of feed options for G5RV, it may provide the answer to your
questions.

Re a "simple dipole" (if that means a half wave dipole, a one band
antenna), I currently use an inverted V dipole on 40m. It is shortened to
cause VSWR=1.5 on RG6 feedline (75 ohm), and the RG6 feedline is of
length (21m) that transforms the feedpoint impedance to nominal 50 ohms
to connect directly to the amplifier (AL-811H) (VSWR1.1 at band centre).
The RG6 has a heap of suppression sleeves threaded over the load end as a
W2DU style balun. Total feedline + balun loss is 0.4dB. There are simple
solutions out there, and feedline doesn't come cheaper than RG6 at US
$0.20/m here in Oz (but you need to be selective in choosing RG6 for this
purpose).

Owen

Coaxial Cable considerations for HF
 

Owen
Thanks for the advice.
My new second antenna is the original I put up: specifically a
store-bought folded dipole from DX Engineering. It is placed orthogonal
(90 deg away from) to the existing G5RV and about 20 feet closer to the
ground. I am using RG / 8U to a 4:1 Balun to 300 Ohm balanced feedline
to the folded dipole. I cut the 300 ohm feedline to optimize the folded
dipole fo 30M and above.

I appreciate the response.

John
AB8O

Owen Duffy wrote:


My article at http://www.vk1od.net/G5RV/index.htm models the efficiency
of a number of feed options for G5RV, it may provide the answer to your
questions.

Re a "simple dipole" (if that means a half wave dipole, a one band
antenna), I currently use an inverted V dipole on 40m. It is shortened to
cause VSWR=1.5 on RG6 feedline (75 ohm), and the RG6 feedline is of
length (21m) that transforms the feedpoint impedance to nominal 50 ohms
to connect directly to the amplifier (AL-811H) (VSWR1.1 at band centre).
The RG6 has a heap of suppression sleeves threaded over the load end as a
W2DU style balun. Total feedline + balun loss is 0.4dB. There are simple
solutions out there, and feedline doesn't come cheaper than RG6 at US
$0.20/m here in Oz (but you need to be selective in choosing RG6 for this
purpose).

Owen

Coaxial Cable considerations for HF
 

John wrote:
Having re-entered ham radio after a 30 year hiatus, I would like to ask
about RG/8U versus other cable types for use in a simple dipole or G5RV
installation with 100W max. transmitter output. In the "good old days"
Low loss "8U" was sort of the standard. There are some newer cable
designations now.

Is there a better "standard" cable for the above use than RG/8U
(specifically Belden 9913 low loss)?

John
AB8O

Hi John,

Some useful information and history is he
http://en.wikipedia.org/wiki/Coaxial_cable. For a given type, you'll find
quality all over the map, from decent to downright crummy. That said, I
recommend a looking at a prospective manufacturer's datasheet before buying.
If there are no specifications available, keep looking!

When it comes to loss/length (for a given cable type), foamed polyethylene
dielectric will be better. Percentage of shielding is probably the next
determining factor. An aluminum foil shield of course will be 100%, but
won't take much flexing before fracturing. Save it for long runs that are
secured in place, and use braided copper or braided copper + foil for other
uses. You'll find most all manufacturers make cables with as much as 97%
braided copper shielding. The last item of concern will be the outer
jacket. PVC is the most common. Some are "non contaminating" or "UV
resistant" types that degrade much slower in sunlight. Use a UV-resistant
type for outdoor applications.

Belden 9913 has a "Semi-Solid Polyethylene" dielectric and can't handle
tight-radius bend. It also has a solid center conductor, which doesn't like
repeated flexing. The shield is "100% coverage Duobond tape" (foil), which
also doesn't like repeated flexing.

RG-58 types are rated to 250W (under matched conditions) safely. If you
plan on running higher power and/or longer runs and/or high standing waves
on the feedline, you should consider something larger. Many hams have used
RG-8X (also called "mini RG-8") with good success. If you're
cost-conscious, this might be a good choice.

Ralph mentioned LMR400 as having a copper coated aluminum center conductor.
It's made by Times Microwave Systems (http://www.timesmicrowave.com/) and is
a solid conductor. Their Ultraflex version (LMR400UF) has a stranded bare
copper inner conductor. He also mentioned Davis RF
(http://www.davisrf.com/) having Buryflex available. As far as I can see,
it's LMR400UF with a different brand name on it. By the way, I've dealt
with them once... very good folks.

Vy 73,
Bryan WA7PRC

Coaxial Cable considerations for HF
 

Bryan wrote:
John wrote:

Having re-entered ham radio after a 30 year hiatus, I would like to ask
about RG/8U versus other cable types for use in a simple dipole or G5RV
installation with 100W max. transmitter output. In the "good old days"
Low loss "8U" was sort of the standard. There are some newer cable
designations now.

Is there a better "standard" cable for the above use than RG/8U
(specifically Belden 9913 low loss)?

John
AB8O


Hi John,

Some useful information and history is he
http://en.wikipedia.org/wiki/Coaxial_cable. For a given type, you'll find
quality all over the map, from decent to downright crummy. That said, I
recommend a looking at a prospective manufacturer's datasheet before buying.
If there are no specifications available, keep looking!

When it comes to loss/length (for a given cable type), foamed polyethylene
dielectric will be better. Percentage of shielding is probably the next
determining factor. An aluminum foil shield of course will be 100%, but
won't take much flexing before fracturing. Save it for long runs that are
secured in place, and use braided copper or braided copper + foil for other
uses. You'll find most all manufacturers make cables with as much as 97%
braided copper shielding. The last item of concern will be the outer
jacket. PVC is the most common. Some are "non contaminating" or "UV
resistant" types that degrade much slower in sunlight. Use a UV-resistant
type for outdoor applications.

Belden 9913 has a "Semi-Solid Polyethylene" dielectric and can't handle
tight-radius bend. It also has a solid center conductor, which doesn't like
repeated flexing. The shield is "100% coverage Duobond tape" (foil), which
also doesn't like repeated flexing.

RG-58 types are rated to 250W (under matched conditions) safely. If you
plan on running higher power and/or longer runs and/or high standing waves
on the feedline, you should consider something larger. Many hams have used
RG-8X (also called "mini RG-8") with good success. If you're
cost-conscious, this might be a good choice.

Ralph mentioned LMR400 as having a copper coated aluminum center conductor.
It's made by Times Microwave Systems (http://www.timesmicrowave.com/) and is
a solid conductor. Their Ultraflex version (LMR400UF) has a stranded bare
copper inner conductor. He also mentioned Davis RF
(http://www.davisrf.com/) having Buryflex available. As far as I can see,
it's LMR400UF with a different brand name on it. By the way, I've dealt
with them once... very good folks.

Vy 73,
Bryan WA7PRC


Thanks, Bryan, for the knowledgeable tips.