How does a J-pole antenna work? AD#36
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- Опубликовано: 20 сен 2024
- Find out how a J-pole amateur radio antenna works! Subscribe: / @davecasler . Ask Dave Playlist: goo.gl/inaQeB.
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One of the best, most straightforward, simplified explanations of a J-Pole I have ever come across. Well done and thanks.
Best explanation of a J-pole I've heard. Now I understand. Keep up the good work. 73.
I fully agree.
But who thought it up in the first place? ... A guy from Poland named Jay?
Absolutely, thanks for explaining it so this dummy can understand.
Amazingly precise yet simple explanation of J-pole. From a Signal Integrity engineer. 73 KE8YVP Jason
Ive watched a dozens videos and have yet to understanf jpole antennas until this one! I just want to thank you for your time and help!!!
Finally, the J-Pole is no longer a mystery! Thank you for this valuable information (as well as how to tune the dang thing). Looking forward to more like this! 73 KE8EAS
Wow!!! I can't believe how easy to understand you made that. Subscribed!
Ditto !
THANK YOU, Dave! You have unlocked one of the mysteries of the universe for me, and I learned lots more along the way. Please keep it up!
Thank you Dave. I finally got it. It's taken years, but I finally get it.
Why didn't someone before you use masking tape and explain the balanced line ?
I now get it, thanks :-)
"And the current goes down" (antenna drops, startled look, instant resume, show must go on!). Thanks for the explanation, very concise and to the point!
Lol, loved when you dropped the J-pole, showsneven a great presenter like you is human. Great explanation of an antenna I've been using for almost 30 years.
;-)
I listened to this right after I purchased a nice breakaway J-Pole, and just now. I've learned a lot since July/August and, now I could actually follow what you were saying. Thanks for all the great videos that you do! You really help us learn out here.
Hello, my call sign is W4LAG from Lee, Florida. I am new to Ham Radio and I have been searching the web to learn more about the hobby. Your videos on RUclips have opened my eyes and hunger to so much more. Thank you for taking the time to help us newbies.
You're welcome!
Thanks Dave. When it comes to electronic theory and practice I need it to be explained to me in simple terminology. I now understand what is happening with this antenna. I appreciate you explaining it for people like me.
Thank you very much for making this video!
I just passed my Technician and General exams this past weekend and have been working hard to get a solid station set up while I wait for my callsign -- I plan on building a J-pole antenna this weekend and now I'll know what I'm doing! Great video, very high quality and very concise, thanks again! 73
Terry, welcome to ham radio!
I just re-watched this excellent video! Best explanation I've ever seen for a J-Pole! Thanks Dave!
Wow. What a fantastic explanation. This is great, I always loved the aesthetics of the design, but had no idea how it actually works.
Best instructor ever...73s.
Total ham noob here. I'm trying to get my license in Canada. This video helped me so much! I learned what's the meaning of 1/2-1/4 wavelengths and this is the best video to understand how an antenna works. Very good job! 73
Thank you.
Thank you for the very clear explanation. I am impressed. I could figure out the J-shape in the name, but didn't know how else it was supposed to work. Thank you!
I built several of these many years ago without understanding the concept of how they worked. Was always amazed at how good they performed with just a handheld hooked up.
Dave: 50 years a ham, and I'm still learning cool stuff. Thanks for revealing the mysteries that make this hobby so fascinating. I'm working on my j-pole now. It's my first, but it certainly won't be my last. Too much fun to build. 73 W0AP
Brilliant explanation! The light bulb just went on, thank you.
Wow! That was simple. Thanks for the neat concise explanation. Now I can build one AND simply explain how it works. 73 KB4ROR
Well done. Thank you. Operating with an Ed Fong J pole. Explains much.
If anyone wants to build one, very cheap and easy, might i suggest this:
1, calculate rough dimensions. Jpoles are pretty forgiving, as are easily tuned. You need to know your long length, your short length, n your gap.
2, find a peice of pipe (i used 12mm aluminium) a bit longer than those 3 added together. Mark your short length + 1/2 pipe diameter, n gap + 1/2 pipe diameter. Cut a 90 (45+45) degree notch at those marked spots.
3, bend at the notches to form your J. Cut 2 peice of pvc conduit (i used 16mm electric) 2x your gap measure. Using the base of your J as a template, drill holes for your short and long sides, with the shortside hole close to the edge, longside roughly middle, and a stub out the other.
4, slide your spacer close to the bottom, then an appropriate hose clamp on each element. The other spacer then goes on. Position around the top of the shorter element, so a strong box is made. In a larger peice of pvc, drill 2 holes to fit the stubs in. I used 24mm water pipe. This is your mount. Mine is fairly short, as it attached to a steel mast, but this could be your mast.
5, attach your coax to the hose clamps, and clamp to the approximate area shown by the calcs. Erect vertical and a halfwave in clear space. SWR. Adjust as needed. I got 1.1 on the second shot.
My point is, although 90% of the J Poles seen on the net are soldered from plumbing fittings, a hacksaw and drill are all you need for a very effective, rugged antenna.
Once tuned, i put a screw in all the joints, and when i got it home, tapped a hole where the coax feed was n secured the coax better. But that was after 6 months of operation at our vacation home. Everything was built from bits lying around, except the $5 ali piece of pipe. Took under an hour to build.
As an added bonus pro-tip, busted up shade tents are a great source of push-up poles. One plastic knuckle breaks, n people chuck the whole lot out. Can very easily put up a 15m mast with a few old shade tents. Just guy them adequate, pretty floppy with all them joints.
Ghetto 2m Jpole in a weekend, most expensive part was the ropes.
Have fun!
Brilliant video . I have used J Poles for many years now I understand how they work . 73 DE G7BWI
I came across this video when I was looking to see if a J-Pole should be grounded.
I've seen enough of your work, Dave, to have a lot of respect for your opinion. Grounded it is, and thanks to this video I see why.
73 de K1PXF
Watched this, then slept on it. Next day watched it again so I can now understand and explain it myself. Thank you Dave!
This is awesome. I've never heard it explained that way. So obvious now. Thanks!
Thanks for the run down. I took notes. I am about to build my first j-pole and this gives me everything I need to know about how they work and what the impedance does. AD5IX
Brilliant description of J Pole - thanks, takes me back many years.
I agree with D. Mckee, this was a wonderful description. I never really understood the "magic" of a J-pole, even though I used a couple of them in my early days.
I had gotten your typical copper J-pole from a fellow ham in the local club I belong to. I made a sort of tripod for it, intending to have it free-standing on my 3rd floor balcony of my apartment. I even found spray paint that sprayed very thick, with a textured result like rough stone. It also had flecks of different colors, and when sprayed with this stuff, the J-pole blended into the brick of the building so well you literally could not see it from the ground. Perfect!
Until I used it to transmit. Then the neighbor downstairs would take a hammer and pound on his ceiling (our floor) to let us know that we were interfering with his electronics. It would seem that our 2 meter signal was coming through on everything from his stereo to his clock radio. As this man slept days and worked nights, if I used 2 meters during the day, it would wake him up, when a garbled mess started yammering into the speaker on his clock radio on his nightstand. This would not do -- the guy could complain to the management and cause real problems! So I had to find an antenna that would still let me reach repeaters in the area AND no longer go through his consumer electronics.
The answer was straightforward. A Moxon loop for 2 meters. I made a pair of them with hookup wire stretched on the ends of an "X" shape of dowel rods secured in the middle. The ends of the two elements had small turnbuckles to adjust the length, to allow them to be tuned, and short pieces of thin shock cord to hold them taut. I mounted each Moxon on a free-standing garden privacy fence section, 7 feet tall and 3 1/2 feet wide. It fit against the ends of our balcony very neatly, and I secured them to the railing with cable ties. The Moxon let me get into area repeaters perfectly, and the neighbor never complained again.
I also operated HF from that apartment, using an MFJ random wire tuner for a while, but then upgrading to their tuner with artificial ground. I would fasten a fishing sinker to the end of a spool of magnet wire and shoot it into the woods across the parking lot below. Then the near end would go to the tuner. I worked stations as far as central Europe on that piece of magnet wire!
Thanks for the info!
Awesome video. I've been building and using J-Poles for years because of their simplicity. But I never really understood how they work. Now I do.
wonderful description specially the way of matching balance to unbalance (I mean the loop) perfectly clear
not only was the video entertaining,I actually learnt something,well done.
By far the best explanation of impedance matching I've seen. Thanks 👍
Best explanation of a J-pole thanks
1:12 "this is what you connect the antenna with"...
I think the word "mount" might have been better here, just a thought.. 🤔
I built a J pole years ago for my scanner and was delighted with the results !
Thanks for the vid, always worth watching and learning !
😎👍☘🍺
This is a really good full explanation of J-pole antenna build, thankyou.
As others have said, superb explanation of how a j-pole works, certainly one of the best.
Thanks !!! I finally get why the connection at the bottom is the way it is...it's the 50ohm matching point !!! I have three j-poles I have built and never really got that. I just made it the best SWR and didn't even think about the 50ohm matching point !... Great explanation. Now for my next one I build I will actually look for the 50 ohm point! That also explains why when I experimented with 75ohm coax the connect point was different !
this was amazing. i mostly understood it in the function of visual RF/wave form, though the explanation of voltage/current/impedance really solidified it.
Great explanation. When I was a kid, I couldn't figure out how a stub-match or gamma match didn't just short out the works. About 10 years ago, I built a 2M J-pole from copper pipe. Worked fantastically. Someone else still uses it. I'm ready to build another for myself.
Would be great if you did an entire series on antenna designs and "how they work". I'm currently reading Joseph Carr's "Practical Antenna Handbook" and despite being extremely technical, learning a great deal about how antennas work. I would like to hear some of the material explained on your show!
I have an old copy of Carrs book and it is well worn. Joseph Carr was a great writer..
love the hidden lols with 101s great video thank you
KF7BWS - Very fine explanation Dave. What a J Pole is, is an end fed zep.
I have made several J antennas for the FM broadcast band, centered at 98MHz, They work amazingly well.
Very good Dave. Very valuable information. We are forming a group of Emergency Communication Specialists here in Saskatchewan and this looks like the dream antenna that we are looking for.
Thanks for the great videos! They are clear and concise and I understand your explanatrions!
Thank you. Your explanation makes a huge difference for this new ham. K9TOB
That's a great explanation of how a J pole works, made simple, Dave. I made one yesterday before watching this. It's a super J pole made from 450 Ohm twin feeder. I don't buy aerials. It's still amazing even after 40+ years of my doing radio, what is a short at D.C. can be 50 Ohm at R.F.
Bill, G4GHB.
It's very pleasant to listen to Dave. I'm still a big n00b in antenna's but I'm getting it a little bit.
This man radiates kind old science teacher vibes and it's amazing
This is still my favorite Ask Dave video
It's one of my favorites too. ;-)
I wish I were smart enough to understand what this guy is taking about. I just passed my Technician exam last weekend. Maybe some day what he said will make sense to me.
Hi David, Can we have a "How does a SLIM JIM antenna work?" - we love your method of explanation and your rich knowledge. Highly Appreciated ! Keep up the great work !
j pole better double than slimjim, the pattern totally diferent my friend.
Actually I see almost identical patterns but the slim jim has to go up higher than 10m (~30ft) to be more effective, check this article: www.hamradio.me/antennas/slimjim-vs-traditional-j-pole-antenna.html
I really enjoy instructional films like this one. Thank you David. 73!
What a great explanation. I always understood a J-pole was 1/2 wave but the lower section/ matching confused me. I had assumed maybe I was dealing with a 3/4 wave in reality, which will match 50 ohms. Thanks.
This was pure genius! Just beginning my research and your wealth of knowledge is apparent. Thanks!
Thank you for your sharing how to make
j-pole antenna..goodjob friend 👍
Very nice explanation and presentation fella. I normally slip into a coma after 1 min of ham tutorials. But I got to the end of yours ok! 73's M0CPU
Wow, excellent job in explaining complicated topics.
Exactly what D. Mckee said! I'm a new ham, and have been baffled by j-poles. Mystery solved! Thanks for your great work!
Ten thumbs up! I finally understand the J-pole thanks to your visual explanation. 73, Bob
Thank you! This is THE BEST explanation I've seen!
Bravo! Thank you for an illuminating explanation! If I understand the matter correctly; At a DC voltage, it is a dead short, but at a VHF frequency, it is not shorted! I am not transmitting or receiving a DC signal so the dead short issue is moot! 73 Russell KE7QXR
Thank you, Dave, I always wondered how the J-Pole didn't short out the way it was designed.
Hey Dave, I built a copper J-pole antenna today. It's Rx is fantastic, but on Tx my swr was 20+. I was worried I needed to rework the feedpoint, but after watching your video I realized that to match a balanced "feedline" (the 1/4 wave parallel section) to my UNbalanced feedline (coax), I needed a balun. After wrapping one up and attaching it, I was down to 1.4:1 on my selected freq. I realized I can get that even lower still with some trimming, as a few MHz below that was getting 1.2:1.
Thanks for the balun advice in there, it really helped me out! 73 KN6AZK
I'm glad it worked out well for you.
Thanks for making this easy to understand! I am researching to get into the radio hobby something I have put off for the last two decades because of elitist and needing good amount of time to learn everything to get things right. This was a great video! I look forward to diving into your channel. Subscribed and up voted.
His pole might not be perfectly straight but he demonstrates his skill with it like a real pro.
73 my dudes.
From magic to simple. Thanks
Ahoy sir!. I'm just getting back into the radio hobby after 24 yrs. I'm more of a listen than talk guy( scanner/SW). I have always been both facinated and intimidated by antennas and theory. Your vid was interesting and very simple to grasp. Would like to learn more about it, and get my entry level amateur license. Good job sir 👍
Thank you!
I’ve been trying to figure out how J Poles work, I was kind of close.
Nice, clear explanation. I would add to be wary of grounding the bottom of the antenna, its supposed to be zero volts, but it never quite is, so you can get unpredictable things happening. Personally, I would keep the antenna insulated from a metallic mast.
Very nicely done Dave!
Your style reminds me of those educational/instructional TV shows back in the 1990s like: The New Yankee Workshop and Bob Vila's Home Again. I like it! One thing i'd like to see you add to your show is, by haps, a "set" in the background. It could be your radio shack or even a workshop since you also show how things are made.
I should ask viewers to submit photos to use as a background. Right now I use a background that came with my editing software, which I modified to include the OG! logo.
As Usual, a great explanation , you make it too easy, Thanks Dave!
I'm a new HAM, and this was an excellent video for me.
Thanks Dave for a great explanation on how they work. Now it makes sense.
Thanks for your videos. They are very informative. Keep up the great work!!
Okay, this makes so much more sense now, I had always heard them described as a 3/4 wave antenna, now I get it, it's really a 1/2 wave with a rather strange feeder. In other words, if you removed the 1/2 wave section above the masking tape, although it would exibit a good VSWR, it would radiat very little to nothing, because, just like open twin lead transmission line, one side cancels out the other because they are 180 degrees out of phase and parallel to one another.
But the most interesting thing about this video is, I have always been in a controversy over which side of this to feed, and I have always feed them on the long side, and with my ground shield on the short leg thinking that it was a ground poise for a 3/4 wavelength antenna. But instead the bottom portion, is infact an impedance matching transformer for a 1/2 wave diapole, which requires no ground plane at all, but it does require a balanced feed which is why I can never get a really good VSWR. it's the same as trying to feed a center fed dipole, or an inverted V without louping the coax or running it through a ferrite bead or two.
I love making things. I will definitely make a few antennas. This is a great explanation to something I found somewhat puzzling. 73s.
Most excellent explanation! Great work.
Thank you for this very in depth video of how the J-pole antenna works.
My Father was enlisted in the Navy ZP-12 Squadron (lighter than air) early to mid 1930's he said the Navy Airships used J-Pole antennas.
absolutely superb, Dave.. Many thanks.. John.. G4EIJ
I knew most of those things separately, but you put it together beautifully in a way that makes sense! Thanks heaps for this video, you got yourself a new subscriber :D Cheers from down under!
What an excellent demo. Well done !
Barry, KU3X
David, I'll join the chorus of kudos for such a wonderful explanation for what is such a mysterious device for many folks. (Hand raised) As you started with the dipole section, I visualized the current/voltage diagrams as seen in the old handbooks. Your explanation of the transmission line section tied it together. Not only did the proverbial light come on, but so many that we can now light up our Christmas tree, hi hi. Your video also indirectly explains why a mobile J-Pole would be impractical. There would be too much stuff (other cars, trucks, trees, curious people) that would interfere with the high impedance section. It also explains why it's best to have these high up in the air
Thanks again! 73 de KA0RFB
You're welcome! And thank you for the kind words!
Thank you for that awesome instructional.
Best explanation I have heard of that antenna. Thanks. Hoping to make one.
Nice explanation, Dave! I really enjoyed the part where you explained how the end-feed works. I'd been wondering about that for some time.
You have a great channel and fantastic teaching method, thanks for sharing your knowledge with us viewers. I have a question for you. I've seen dual band J-Poles 144/440mhz fabricated in a manner to where the upper portion of the antenna is 440,and the lower section is 144, separating the two bandwidths is an insulator coupled with what appears to be a copper wire circling the antenna perpendicular to the radiating element, I guess you can call it a load ???. I apologize if my description is confusing, don't know how else to describe the contraption. Can you explain how the antenna works???.
Kind regards, Eric Dee.
Great explanation. Building my first one - amazingly simple to build but harder to understand - thankyou.
Dave: One of the best educational RUclips videos I've seen; not only in the ham radio genre, but period. So I built a center loaded J-pole from some plans that is supposed to be dual band. Where does 70cm come in to the equation?
Thanks again,
Todd (AD0RR)
Hi Todd, I'm going to do a video soon building a kit 2-band J-pole, and I'll explain how it works on 70cm. Thanks for your suggestion! 73, Dave
That the coolest thing I learned today. Thank you Dave
Happy New year Dave. Wow I have always wondered how one of these things work. That has to be the best video I have ever seen regarding a j pole. I guess it's the same for a slim Jim.
Fantastic video.
Motters
M7TRS 73's
Glad it was helpful! Yes, slim jims work the same way.
I have always wondered what the science was regarding a j-pole! Very well explained!!! Fantastic video!
Kind regards,
Simon
M0SYS
THANK YOU!
Someone finally made it make sense for me.
Very very well explained good job