Amateur Radio Stack Exchange
Amateur Radio Stack Exchange

Questions tagged [j-pole]

13 questions
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3 answers

How would I calculate antenna gain?

The concept of antenna gain is pretty important for calculation of link budget and is something I've had contact with. I know that it tells me how focused the waves emitted by the antenna are and I know how to read antenna gain charts. What I don't…
AndrejaKo
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How to calculate single-stub match (general case)?

I'm trying to build a 1/2 wave "Coaxial J-Pole" antenna, similar to what is described here: Such an antenna would be great for stringing up in a tree when operating remotely, no tuner needed. The trick is that I'm trying to use 75Ω RG6 coax for the…
Robert Quattlebaum
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6
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2 answers

Why don't J-Poles need to be grounded?

I'm building my first J-Pole and the different projects and articles I read about differ slightly but one commonility is a J-Pole does not need to be grounded. Why is that? I read that it is optional to ground the J-Pole antenna to deal against…
john_ham_radio
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4
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1 answer

How do dual band J poles work?

My understanding is a J pole is a $\frac{1}{2} \lambda$ dipole attached to a $\frac{1}{4} \lambda$ impedance matching element. How does this dual band work? What acts as the impedance matching element and what is the radiating element? Does the…
rsn
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4
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4 answers

Is a copper J-Pole antenna better than a Slim Jim for transmitting?

I live in a fairly sheltered valley but there are several hill-top VHF repeaters that I can receive very well. However the one repeater in particular I want to transmit to, I can't reach well. I know my signal is reaching it, because it will…
Brad McCarty
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2 answers

Will spray painting a J-pole impede functionality?

I'm building a J-pole antenna like the one specified here: https://www.sysjolt.com/2022/building-a-j-pole As you can see it's made of copper pipe and I'd like to camouflage the antennae a little bit. Will using spray paint degrade the performance of…
john_ham_radio
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3
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1 answer

Phasing stub length for colinear 5/8λ?

I've been designing a "Super J-Pole" for 10M in MMANA-GAL, but I'm designing it having two 5/8λ sections. However, I came across this picture: Various J-Poles types diagram indicating the phasing stub for a colinear 5/8λ antenna is a λ/4, is that…
Louis Seaman
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3 answers

Mounting a J-Pole and Yagi on the same mast

I have two 2-meter antennas, a copper J-Pole and a Hy-Gain VB-25FM. The J-Pole is my all-around antenna, what I use for general 2 meter stuff like connecting to my local repeaters using my main 2-meter radio. The VB-25FM will be used to establish a…
user16442
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Is a J-pole an appropriate antenna for mounting to a steel handrail?

Last year, a group of us placed a battery-powered 2m digipeater using a J-pole antenna on a mountaintop. We're planning on doing the same this year except we plan to use a surge arrestor from the feed line ground to the metal railing. Is a J-pole…
watkipet
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baofeng UV-5RA has issues with j-pole

I have a baofeng UV-5RA which doesn't seem to receive properly with my j-pole antenna. my dad's radio (same model, different firmware) receives without a problem, so it's a radio issue. if I go into the menu by pressing the menu button, suddenly it…
Trevader2413
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Measured forward power less than "usual"

I've just tried making my own J pole antenna. While matching for lowest SWR on the SWR meter, I noticed that my FTM400 didn't show 5 W forward power. I hardly saw the reflected power needle move so I increased the power to 20 W just to have a quick…
Hans Neve
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J Pole, what is the best way to deal with Common Mode Current?

I am planning on utilising a ferrite choke on a J Pole antenna for CMC. Placement directly on the feedpoint poses possible mechanical restraints. Is it okay to place it a quarter wave down the coaxial feed line in free space from the feed point. Is…
Francis Archibald
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Generally speaking what might one expect from a J-pole based on PVC covered in tinned braid?

Would the skin effect provide benefits or would capacitance/inductance cause problems?
NonYaBidnezz
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