2 Meter Coax Feed, What to use?

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Robby Cherry:
I just built my first JPole to be used with 2 meters- voice and some packet work.  I started searching this site and some others for what coax I should use?  I hope to get it up about 20 feet, maybe more.  I live in a subdivision so I'm going to try to hide it in a cluster of trees.  The entire run should be under 50 feet.  

What coax would you use and why?  I have found several messages and they all seem to suggest something different.  I have heard the best is: RG8/U, RG213 and Wireman106.

Thanks in advance for any advise.

73 de kd4wuo

Dale Hunt:
There is no one BEST type of feedline.  Like everything
else in ham radio, there are tradeoffs that ay lead you
to choose one thing or something else, but there is no
right or wrong answer.

Generally the tradeoffs in coax are cost vs. attenuation.
(There are also some mechanical issues, for example, if
you want to bury the feedline underground without using
a protective conduit.)  For a 50' run on 2m, any of the
RG-213 type cables should work just fine.  RG-213 is a
military specification number, and different manufacturers
make cables that meet this spec.  RG-8 is an out-of-date
military number, so manufactures can stamp this on any
sort of cable they want to without regard to quality or
characteristics.  Some of it is good, and some isn't.
Unfortunately, it is difficult to tell from the outside.

RG-213 (and RG-8) coax is just under 1/2 in diameter.

Now, every type of coax cable will have loss, and the
loss will be higher as you go higher in frequency.  
Reputable cable manufacturers will have tables showing
how many dB of loss their cables will have on different
frequencies, so you can compare them.  If you find a
type of cable with a loss of 2dB/100 feet, then the
loss in your 50 foot length will be 1dB (the loss in dB
is linear with length.)

Now let's look at other types of cable.  RG-58 is a common
type, about half the diameter of RG-213 and considerably
cheaper per foot.  It might have a loss of 5dB / 100 feet
at 2m.  (I'm inventing numbers here - hopefully someone
else will come along and point you to the right ones.
But these will give you a sense of the tradeoffs.)
So a 50' length will have a loss of 2.5dB - or about 40%
of your power won't make it to the antenna.  (A loss of
3dB is half your power.)  Now, YOU have to decide whether
the money saves is worth the 1.5dB difference in radiated
power between the two cable types.  For hitting the local
repeater or chatting locally, this may make no practical
difference.  For marginal paths or weak signal work,
this may sometimes be the difference between making a
contact and not.

You will also see refernces to RG-8X (or RG-8M from
Radio Shack): this is an intermediate-sized coax cable
with foam insulation and lower losses than RG-58.  Again,
the designator is NOT an official MIL-SPEC designation,
so there is a wide variation in characteristics among
different manufacturers.  But this cable would also be
usable, again with a tradeoff between cost and loss.

Unless cost is the overriding factor, I'd suggest the
RG-213 type.  Quality coax is a good investment, but
don't over-buy the higher grades/types.  (Remember to
make sure the ends are sealed to keep water out - that
is a quick way to ruin your investment.)  But if cost is
critical and someone offers you chunks of one of the
other cables, they would still be usable.  (But anything
smaller than 3/8" diameter is going to be TOO lossy.)

Robby Cherry:
Great reply, thanks for the help!

Tim Savage:
Yes, it's true, there is much to learn about coax but
the main thing is , What are your expectations ?
I have used all sorts of coax over the years and even
made some of my own. If you are not a perfectionist
and only want reasonable performance then use what
you have or can afford. Other types of coax that
work well are LMR-400 and Belden 9913 . There are
dozens of good brands and types of coax out there.
It is up to you to do the research or the
experimenting. This is a learning hobby, that's the
part I like best.
73 and good luck,
Tim
WA4PTZ

Kenneth Meyer:
For a coax run of 50 feet or less, Most any type of RG-8 size coax should be suitable for 2 meters.

For anything much more than 50 feet, Times LMR-400 is the good stuff used by the pros on commercial two way systems.
RG-213 is a great coax for HF use, Not the best for VHF/UHF
Belden 9913 is one to be very wary of. Several versions of it have had all sorts of problems.

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