J Pole Project

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TomX

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Jul 31, 2014
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Hello Everyone,

I've been on the air for a little over 2 weeks and having a lot of fun. This week my friend and I built a 2m J pole (see attached). Followed instructions/advise on sites like K0BET.com Radio Operator and J POLE ANTENNA DESIGN CALCULATOR by K4ABT. So far I am really pleased with the results.

My goal was to extend the range of my HT so I could hit some local repeaters. It worked and the folks I've been chatting up have generally given good signal reports.

Just wanted to share that with everyone. A good project if you're on a limited budget and seems to work for improving HT performance.

--Tom
 

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nanZor

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Nice job!!

Clamp a few ferrites over the coax near the feedpoint.

While it will work without it, J-poles being very unbalanced, have a lot of common mode current on the feedline, skewing the pattern. This may or may not be very important in your situation.

There are actually 3 transitions in a j-pole. 1) An end-fed unbalanced half-wave to: 2) balanced quarter-wave stub to: 3) unbalanced feedline.

At least 4 of the Radio Shack 273-105 clamp-on ferrites would do, as they are #43 mix, good for 30-300mhz. Expensive, and there are other alternatives, but good for the impulsive fix.
 

AK9R

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Good for you, TomX! A lot of new hams try to get on the air with just a handheld and rubber duck only to wonder why everyone tells them they are noisy into the local repeater. A simple antenna in a fixed location can really improve a handheld's coverage.
 

TomX

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Pittsburgh, PA
Nice job!!

Clamp a few ferrites over the coax near the feedpoint.

While it will work without it, J-poles being very unbalanced, have a lot of common mode current on the feedline, skewing the pattern. This may or may not be very important in your situation.

There are actually 3 transitions in a j-pole. 1) An end-fed unbalanced half-wave to: 2) balanced quarter-wave stub to: 3) unbalanced feedline.

At least 4 of the Radio Shack 273-105 clamp-on ferrites would do, as they are #43 mix, good for 30-300mhz. Expensive, and there are other alternatives, but good for the impulsive fix.

hertzian, thanks for the advise on that. Most of the plans I saw say to make a choke out of 4 - 5 turns of coax right at the feed point. Problem is that I made a beginners mistake and bought LMR-400 for my feed line, not realizing that LMR-400 is like a garden hose. The clamp-on ferrites sound like something that will work,even with my LMR-400.

Thanks.

--Tom
 

hhrj

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J-poles are my favorite, made 2, first was for 2m in 1992 using plans out of 73's magazine. Didn't work very well and I took it to my friends in Fl. They said the feed was on the wrong side and I showed them the as built plans. They got out the torch and took it apart. Dan pulled a pair of machined plexiglass spacers out of his tool box that spaced the elements. They cut the short element about an inch shorter and soldered a cap with a threaded brass bushing. A brass carriage bolt and lock nut were screwed in the cap. After the feed was corrected the pole was set up in the back yard with my coax and connected the Bird with my HT. The screw was adjusted and locked. I've used this pole in a lot of locations with great results.

In 1998 I needed a better antenna for my aviation scanner so I broke out the tubing cutter and torch again. This one is tuned for the center of the band and it too worked well.

Still have both of them, stored in the attic.

HHRJ
 

dksac2

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Great job !
You can also make a very good 2m/70CM portable antenna from 450 ohm twin lead. I made one a while ago and used it with a second radio when I was net control for a large bike race. The twin lead antenna worked almost as good as my vertical. It's approx. about 3 1/2 foot long. I used an "N" connector on it for the UHF.
I no longer have the plans, but a check on the net should find you what you need to build one.

Enjoy your new J pole and you did good using the LMR 400. The clamp on ferrites will do a good job uncoupling the feed line.

73's John
 

SCPD

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twin lead telecommunications

Great job !
You can also make a very good 2m/70CM portable antenna from 450 ohm twin lead. I made one a while ago and used it with a second radio when I was net control for a large bike race. The twin lead antenna worked almost as good as my vertical. It's approx. about 3 1/2 foot long. I used an "N" connector on it for the UHF.
I no longer have the plans, but a check on the net should find you what you need to build one.

Enjoy your new J pole and you did good using the LMR 400. The clamp on ferrites will do a good job uncoupling the feed line.

73's John

I've made a few of those, and shoved 'em down a piece of pvc pipe and mounted it.
Worked well.
And like you said, many plans for those are on the 'net.
 

dksac2

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I've made a few of those, and shoved 'em down a piece of pvc pipe and mounted it.
Worked well.
And like you said, many plans for those are on the 'net.

I have to admit, I was surprised at just how well the duel band 450 ohm antenna worked. The SWR was very good and the range excellent. I just used plastic wire ties to attach it to a wooden dowel and clamped it to the top of a 30' fiberglass pole.
It's really just for temp. use at home or use in the field. It rolls up into a small package. I use about 30' of LMR 240 and pull it up into a tree with some 1/8" rope. The LMR 240 has about the least amount of loss of any of the skinny coax.
The 15 meter Moxon I made sure works great also. I want to put it up for full time use, but with winter here now, I'll have to wait until spring.
Nothing like rolling your own.

John
 

Geeper

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Nov 23, 2014
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Meyers,Ca.
Looks great! nice Job! I built one 7 years ago it has been moved to a high corner of my shop. Now a back up 2m antenna during summer lightning storms so I can check into the Reno Skywarn net.
 
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