Am I a trend setter,dreamer or has someone already done this?

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1hardyanimal

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Good day my community of learners and Elmer’s!!!
So I have had the inclination lately that for my home base I am going to go with a homebrew J-pole out of either stainless rod or tube or maybe coper pipe. I can TIG weld stainless or sweat the copper, whatever it takes.
BUT here is what I am leaning towards. As I am a pretty wishy-washy purchaser and what tickles my fancy this week with knobs and dials and meters and displays this week, can easily be distracted next week by buttons and keypads and digitized displays. With this in mind I have an idea to build an easily tunable DUAL BAND 2m/70cm J-pole.
My thought is that were I connect my SO-239 panel, that I will be if copper, soldering that pipe strap/utility strap with all of the holes on each side of the construct. This way that where the shield/ground is normally soldered it can be fastened with a thumb screw, and where the core is normally wire, I will use thin threaded rod, so it can pass through the opposite side and be secured with a thumb screw. The idea here is to easily move it up and down to tune it initially, and then again for each radio that I may use swap out on this antenna…thoughts? Has this already been done and failed, am I a pioneer, or just a newb with his head in the clouds?
 

zz0468

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A properly matched jpole doesn't need to be retuned for each different radio you hook to it. Your idea would work, but should be completely unnecessary.
 

jonwienke

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Tuning is based on frequency, not the radio.
 

toastycookies

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Good day my community of learners and Elmer’s!!!
So I have had the inclination lately that for my home base I am going to go with a homebrew J-pole out of either stainless rod or tube or maybe coper pipe. I can TIG weld stainless or sweat the copper, whatever it takes.
BUT here is what I am leaning towards. As I am a pretty wishy-washy purchaser and what tickles my fancy this week with knobs and dials and meters and displays this week, can easily be distracted next week by buttons and keypads and digitized displays. With this in mind I have an idea to build an easily tunable DUAL BAND 2m/70cm J-pole.
My thought is that were I connect my SO-239 panel, that I will be if copper, soldering that pipe strap/utility strap with all of the holes on each side of the construct. This way that where the shield/ground is normally soldered it can be fastened with a thumb screw, and where the core is normally wire, I will use thin threaded rod, so it can pass through the opposite side and be secured with a thumb screw. The idea here is to easily move it up and down to tune it initially, and then again for each radio that I may use swap out on this antenna…thoughts? Has this already been done and failed, am I a pioneer, or just a newb with his head in the clouds?
not exactly sure what you are trying to do but dual band j poles are a thing.

Arrow Antenna J Poles 2m 146 70cm 440 OSJ
 

cmdrwill

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Arrow Antenna J Pole 2m 146 70cm 440 OSJ IS a way MUCH better antenna, and has much better bandwidth. And no funky RF backing down the coax cable.

And if you would like to build one the Coax mount is available at most CB truck stop stores.

Also have a couple of the Arrow groundplanes, excellent for temporary/ event operation.
 

KC4RAF

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As others' have posted, the antenna doesn't need re-tuning with different transceivers/transmitters. Once tuned, it's tuned to THAT FREQUENCY, not the transceivers/transmitters. Your idea is over kill for a simple J-Pole. But it's your idea, and it will give you experience in building antennas.
 

1hardyanimal

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Yeah I just within the last few days discovered that there was dual band J-poles, and in the last couple month found that there was such an animal as a J-pole. My ignorance was in that they did not need to be “matched” to a radio like a whip does with an SWR meter each time it is changed. By the sounds of it, A J-pole can be in theory, “Built properly” and have good SWR, and in essence, double checked with a meter.
SO if you have a “known to be good J-pole, tested with an SWR meter etc. against one radio, then it will match with most if not all radio’s, and not need any further tuning? If that is the case I like it, I am not a huge fan of traversing my roof ten times.
Next question is, when tuning a J-pole, can I do this successfully just say, 10 feet off the ground with 50 feet of cable, then put it 35 feet up off the ground with 70 feet of coax on my roof and have the same tune? Or if I know I need 70 foot of coax for the run should I tune it with the 70 feet of coax, still only ten feet off the ground, unhook everything, re-route it and then do the install with my now tuned J-pole?

Very excited and cannot wait for my broken leg to heal to get this thing done. The idea is I can build it now, If I can mount it and run it ten feet off the ground on my deck while I heal and then on the roof this summer when I am better…thoughts, ideas?
 

nd5y

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Next question is, when tuning a J-pole, can I do this successfully just say, 10 feet off the ground with 50 feet of cable, then put it 35 feet up off the ground with 70 feet of coax on my roof and have the same tune? Or if I know I need 70 foot of coax for the run should I tune it with the 70 feet of coax, still only ten feet off the ground, unhook everything, re-route it and then do the install with my now tuned J-pole?
You can try tuning it close to the ground but don't be surprised if everything changes in it's permanent mounting position.

If you want to learn more about j-poles read End-fed Vertical and J-pole
 

mrweather

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Ideally you want to tune the antenna in its final mounting position. And also ideally you want have your tuning instrument as close to the antenna feedpoint as possible.

Reality is I've tuned j-poles stuck to a 7' patio umbrella pole. And as long as I was as far away from other metal objects as possible, the tuning barely changed after I permanently mounted the antenna.
 

KC4RAF

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...animal, below is a link to a great website that shares his knowledge in the art of building amateur radio antennas.

Martin E. Meserve - K7MEM

I've used his site in building a couple of VHF/UHF yagis; and I got good reports about the signals from them.
Some of the theory involved may seem daunting, but after experimenting, you'll learn a lot.
BTW, Martin is a member of RR.
 

1hardyanimal

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Durand,Mi.
LOL!!!! I just built a ground plant, and have it tuned so beautifully!!! I found a section of PVC that a spray paint lid slid over like it was made for it, I straightened out 5 pieces of Romex, soldered my SO-239 center element and ran eyelets for the radials and bent them all down at a 45, then hot glued it up (about 3 sticks worth) for weather protection, it’s on my deck rail with a wood clamp, so about…13 feet off the ground and I am pulling in maybe all of lower Michigan with it!!! Wait till I get my License and we will see what that baby works!!!
I will most certainly have it tuned for my final destination. I am a huge believer in the “well-oiled-machine”. I have always prided myself as being known as “the guy to buy stuff from” because I try my best to not cut corners and do things right. I know how much damage can be done to a radio if that antenna is not matched up right.
 

cmdrwill

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I know how much damage can be done to a radio if that antenna is not matched up right.
Glad to see you understand "matching antennas". I see lots of messed up radio operation due to mis matched antennas. Seems the Hams are the worst offenders of antenna "matching". Lots of repair work due to wrong or mis matched antennas.
 

1hardyanimal

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Durand,Mi.
I believe I owned my first SWR meter at age 13 or 14, however I alllllllways still have to re-read the instructions as it is far to long between uses 
 
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