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1-5 of 5 messages
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Page 1 of 1
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J-pole or dipole
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Reply
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by KC9AIK on May 24, 2002
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Hi,
I want to build a j-pole or dipole antenna by myself, but I don't really know, which one is better for my purposes. It should be for a 2 meter handheld, just that I can boost my range a little. But I heard a some people saying, j-poles are more likely to be used for packet radio, and not for phone. Is that true, or does it not really matter? I also would be intrested, how the directional pattern of a j-pole looks like (like the pattern of a vertical antenna is omnidirectional...). I have a lot of information about dipoles so, this is not so big of a problem.
thanx for your help,
Kilian
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RE: J-pole or dipole
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Reply
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by KE4DRN on May 24, 2002
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Hi,
Not to talk you out of the J pole or dipole but
here is a link to a easy to build, low cost antenna
for two meters that uses common # 14 wire THHN
available at local home centers. PVC is used for
the frame.
http://www.cebik.com/hs.html
The antenna is called the half square.
I built a few of these and they work great !
After you build this antenna you will be on the air
and will be able to take time and build the jpole.
73 james
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RE: J-pole or dipole
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Reply
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by KC9AIK on May 25, 2002
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Thank you for your quick reply. But I forgot to mention one thing. I wanted to have a dipole or j-pole, because it is easier to handle, if you travel around (like for camping). For a real base installation, your suggestion would probably be the better way. But I'm more searching for a solution, where I could store the antenna in my backpack and it wouldn't take that much space away.
But thanx anyway, the web- adress is a great page, and it helped me a lot informing myself about antennas. It is really intresting. Maybe i find there another really good solution.
73 Kilian
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RE: J-pole or dipole
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Reply
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by WA5EE on May 26, 2002
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I had terrific results from my roll-up j-pole hanging in motel room windows all over the country.It improved the range of my HT so much , it was hard to believe.I bought mine ready-made from MFJ , but you can build one from TV twin lead using the info at
http://hamgate1.sunyerie.edu/races/antenna/pocket.htm
Good luck ,
Russ , WA5EE
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RE: J-pole or dipole
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Reply
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by WB6BYU on June 11, 2002
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Kilian -
Actually, the only difference between a J-pole and a dipole is the
feed system. Both use a half-wave radiator, so there is no
theoretical difference in performance between them.
Personally, I find the J-pole approach a bit easier, since the
coax cable is not in the radiation pattern of the antenna element.
This is a common problem with vertical dipoles (though it can be
easily solved by running the coax THROUGH the lower half of the
dipole - this is called a "coaxial dipole", and is also quite easy
to build.
Since an earlier poster gave you a link to the J-pole instructions,
here is how you can make a "coaxial dipole." Read them both and
choose which one you think would be easiest for you to build,
given your own skills, resources, and interests. Performance should
be the same for each. (Or build them both, just for the experience!)
I've built this antenna while giving a talk on antennas, to show
how easy it is. Take a length of coax and remove about 24" (65cm)
of the outer insulation from one end. (OK, I did this in advance of
my talk, so I wouldn't cut myself with the knife in front of everyone.)
Push the braid back away from the end, bunching it up at the end
of the outer insulation. As you push, the braid will increase in
diameter. As it does, push it back over the insulation and keep
working it until all the braid has been "folded back" over the rest
of the coax. Smooth out the braid, and trim both elements (braid
and exposed center conductor) to about 19" (50cm). Tie a string
to the end of the center conductor to hang it, put a connector on
the other end of the coax, and you are ready to go.
I often see 25' of RG-58 computer coax with BNC connectors for
$2 or less: one length makes two of these antennas.
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