How to build a J-pole with twinlead: Ask Dave #42
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- เผยแพร่เมื่อ 8 ก.พ. 2025
- The Amateur Radio Supplies 2m/70cm Dual Band J-pole kit is the subject. This video takes you through the entire build process including testing. I ran into some issues, but fixed them. Subscribe: / @davecasler . Ask Dave Playlist: goo.gl/inaQeB. Tip Jar: ke0og.net/tip-jar. Website to order antenna is www.amateurradi.... Note that I bought and paid for this kit and have no relationship to the manufacturer.
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Dave, you’ve assembled a great catalog of how-to almost everything Ham Radio. That catalog is sure to be used as a reference for many, many years. I did 10 years as an Army radio-teletype operator, and as I got out, here came the internet so I forgot everything. I bounce around as needed, really helping bring it all back and more. Thank you. Stay safe. 73
I built a 3m “twinlead J-Pole” years ago, for an FM receiver (tuned to 98MHz) .. worked great ...
Great video Dave. Thank you. I was one of the people who asked about these antennas. After building one myself, you talked me through trouble-shooting it. Thanks again for your commitment to us new HAMS.
Dave, you're great. I hope you never stop making these videos!
I finally followed up on the General Class license you helped me get by getting an ICOM-7300 attached to an attic 20m 1/2-Wave Dipole in my attic and have been having a lot of fun despite the solar conditions and the attic thing. Maybe one of these days we'll qso over the airwaves. In the mean time, 73s! and happy new year!
Thank you! 73, Dave, KEØOG
Thats a very tricky antenna build with the chopping/cutting, shorting out, but it was very interesting to watch and see how the J pole works. Thanks for taking the time to build and share!
Thanks for the video Dave. I have been trying to build this antenna, following the directions, found in QST, and couldn't get it even close. I built it with your dimensions, and it worked! So far I have a 1.1 to 1 on 462mHz (GMRS ), Vhf is still pretty high, but I'm still working on it. Again thanks
When you hold up instructions, at least check that its in focus, and keep your fingers and hands off the document so we can read it. The instructions actually look well detailed and easy to follow for one of the easist to build antennas.
I chose to do the coax solder attachment last .. had to do testing to find the place of lowest SWR at the spot in the band needed ...
KF7BWS - Very fine explanation Dave. What a J Pole is, is an end fed zep.
Just FYI . If you push the thin end of a zip tie back into the locking end, it will lift the locking tooth and the zip tie can be slipped off. I reuse zipties a lot. Also, good to know if your hands get zip tied together.
Thanks for the tip
"Zip-ties" as you call them are (at BEST) a one-shot deal. We used to call them "Tie-wraps", and no self-respecting telephone man would be caught w/ one.
Some zip ties are specifically made to be re-used, too. It only takes another couple mm of material sticking out the back of the lock; more manufacturers should do this, but of course it would eat into their profits...
Got a bunch of baofengs. Chirp trimmed. To work as monitors, and J-poles seem cheep.. I'm watching to learn. A frend passed. (N8rim) and I recived a big spool of rgu-58. Half ways there. Tks Fer good info. Kv4li.
Thank you for showing what a labor that would be if I attempted it myself. Of course, had I tried, I would have end up a finger or two in the shrink wrap...And probably an eye along with the remainder of my youth.
That really was a lot of work, and just the kind of thing I like to buy ready made if it's not too terribly expensive. Thanks for the lesson.
Dave just some info for you. We were making these roll up jpoles for many years and you dont need the short piece of small coax in the center, ours had a notch cut out of one side of the center and was made from cheep 300 ohm tv flat lead. and was 1 to 1 swr for 146 mhz you just needed to cut it in the right spots the bottom was the same and we made them for several different freqs. there are online calculators and info on cutting them THANKS Chuck :)
This is the link for info on my version www.wb5cxc.com/twinld_jpoles.html
The link leads to spam. It should be removed.
Now tell us about one fully assembled! :)
SLIM JIM ANTENNA
The main advantage of it is it's very low angle of radiation, reported to be around 10 degrees or less to the horizon which makes it "perform" much better than standard J poles because the radiation pattern is much closer to the horizon where you want it in the first place! This is the major plus for the Slim Jim type antenna
I haven't read through the comments yet, but if you take your razor knife, and gently push on the tab inside of the cable ties, you can slide it out and reuse it later. You can use a small screwdriver as well (probably preferred over the knife).
And now folks are making reusable cable ties that make the removal process easier.
Where do you get the twin lead if you want to build your own?
Great work on the video Dave.
Thanks David!
This might be a silly question but here goes. You added a 1.25" jumper because you said the measurements were off. But when you calculated it out near the end, you were 1.2" long. So would you have been better off not putting that jumper in, after all?
I think the answer to that lies in the SWR in the 70cm band. In other words if the 70cm resonance is at too low of a frequency then the added jumper hurt things. If the 70cm resonance is at the desired frequency then the jumper was the right choice. Unfortunate that the instructions were so inconsistent.
Hi David. Thanks for your video, very good, I can see thinks I could not see in other videos, I like your video definition, please keep it like that. I learnt a lot. Thanks again
You are welcome! I'm glad you find the videos useful. 73, Dave
Excellent video. 👍
But, as a NASA certified flight harness fabricator, LOL....I do have to admit to cringing a few times at your fabrication methods.
Thanks for the RF tuning edumaction.
Keep up the good work turning us newbies into better radio techs.
I'm very prouda ya, Mr. NASA tech...
Ed fong design, I have had little luck getting these resonant
Thank you for sharing this! It looks like a fun project which I think I may attempt, sourcing the materials myself instead of the kit.
I am having difficulty locating RG303. When I compare the performance specs for RG8x and RG303, I do not see anything of real significant difference. Do you think that a similarly sized section of the RG8x might be substituted for the RG303? What impact do you think it will have on the performance?
Go ahead and give it a try. Read through all the comments, as there are many suggestions for alternative ways to make a dual-band J-pole. 73, Dave
+David Casler, From the looks of it, your kit is the original DBJ-1 by Dr. Ed Fong. See "edsantennas.weebly.com/uploads/2/9/3/5/29358461/dbj-2_qst.pdf", figure 3. The DBJ-1 was intended to be inside a PVC pipe.
Dr. Fong has a newer design, the DBJ-2 (see tfigure 4 in the PDF referenced above) which isn't required to be enclosed inside a PVC pipe.
Dr. Fong sells his antennas on eBay ("stores.ebay.com/antennasiqn/"). I have a DBJ-1 and DBJ-2 and the are excellent!
Thanks for validating my decision to purchase one already assembled. :)
Thanks for the links. 73
I wonder how this works at all with the coax basically shorted to ground?
I have built an 11 meter jpole just this week but struggling to get a useable swr.
Man this twinlead looks strong and hardy! The stuff I have is incredibly fragile. Building Ed Fong's antenna might be impossible.
Great video!
Construction seemed more difficult than it should be. Trying to splice stranded wire together is a pain unless its lightly tinned, but lightly tinning takes practice otherwise the strand becomes a stiff piece of glued wire that is really difficult to bend. Sorry to see you had some difficulty. I do too but isn't it fun, in macabre way. hi hi
Indeed, the kit was more difficult to build than perhaps it should have been. The end product, though, works well.
I feel better knowing that I'm not the only one who injures myself every time I make an antenna, I hope that heals up quick for ya! 73s K8GLX
I figure it isn't a good project unless I have some blood in it ;-)
GREAT VID KE0OG! MY QUESTION IS BOUT YOUR ANTENNA ANALYZER I NOTICED YOURS DIDNT SEEM TO BE AFFECTED BY THE TOUCH. I HAVE A MFJ 269C AND WHEN MY HAND GETS CLOSE TO THE KNOBS IT SHOWS A FAULSE READING (USUALLY NEEDLES MOVE UPWARD) HIGHER THAN IF MY HAND IS AWAY. ANY INSIGHT ON THIS CAUSE WHEN I TUNE TO A PATICULAR PRESICE MEASUREMENT ITS A PAIN HAVING TO ADJUST THEN REMOVE HAND AWAY FROM ANALYZER THEN ADJUST AGAIN REPETEDLY ECT...THANKS W9DES
That sounds like a real pain! I've never seen that problem with my analyzer. One thing you might be able to do if you're testing from indoors is to connect your analyzer to your station's ground system. That might give some help, but doesn't help if you're doing this outdoors. If I were you I'd contact MFJ, because this is definitely abnormal behavior. Good luck! 73, Dave, KEØOG
ITS BEEN LIKE THAT FROM DAY ONE AND YES IT BECOMES A PAIN NOTIN I CANT DEAL WITH BUT I NOTICED YOURS DIDNT DO IT SO I WAS COURIOUS ILL CONTACT THEM SEE WHAT THEY SAY ABOUT IT THANKS FOR THE INSIGHT DAVE KE0OG,W9DES CLEAR.
Hi Dave! If I build one for 11 meter it should be close to 25ft tall according to Dave Tadloc's build.
Would it be possible to pull it up like a flag?
I was thinking of getting 3 - 10ft top fence rails for a mast.
My concern is would the metal mast interfere with the antenna?
Is it possible to build the same antenna for 6m and 10m?
Yes, in theory. But you may need to do lots of experimentation. Perhaps somewhere on the Internet there are some design equations. Good luck, and when you get your design working, publish it! 73, Dave, KEØOG
Great question
Hi how to build VECTOR 400 ( jpole) at home... any calculator= thank you in advance.
Tnx for share.
Another great and inspiration video in my subscriptions.
U are the "guy" !
73 from Brasil
hello mr 73. or can i say dr 73
ubscribed bythe way
Hi dave
I have a question and was wondering if you could help. I have purchased a baeofeng 5R hand held and wanted to make an antenna for home use so I can actually reach the local repeater. why antenna should I consider making from scratch dave? many thanks in advance
Hello Dave. I am very last to the game here. Would there be any difference in performance between 300ohm and 450ohm ladder line slim Jim?
Motters M7TRS 73's
If the 300 ohm and 450 ohm twin lead/ladder/window line have different velocity factors their length measurements will be different.
HI DAVID I read that on the sellers site
Excellent!
i dont understand what the coax in the middle is for? if your just shorting the ends out?
It actually is a matching stub. It's shorted at one end and open at the other.
Hi David! I was just wondering. If I had say 4000 watts, I could get out many places around the world correct?
If I understand correctly I'm not going to receive no where near that kind of range unless someone on the other end is pushing the same amount of power.
You can only get so much receive out of an antenna even if its the best of best setups is this correct?
Thanks!
No, propagation is weirder than that. Simply increasing power marginally increases listening range. Clear channel AM broadcast stations use about 50,000 watts. FM and TV stations can be several hundred thousand watts. Yet during the day these signals can go perhaps 100 to 200 watts. Power does not equate to distance, although when conditions are marginal, it can help. To answer your question, yes, the EIRP of your station needs to be about the same as the EIRP of the other station, all things being equal, for marginal signal reception. Hams are "supposed to" use the minimum power required to have communications.
@@davecasler Thanks for the response David!😀
Hi Dave, question, I live in an apartment, are there any 2m/70cm antenna options for me?
I recently saw an article about using copper tape to create a Jpole on a window. Try a Google search.
Went to order the antenna clicked check out quoted $60 for shipping to Canada... didn’t order antenna
Whew!
Order the real thing instead of this clone
I wonder if US Amateur Radio suppliers REALLY understand that the cost of single item postage from the USA, is generally what stops the majority of hams worldwide from buying their products.
Hi Dave, luv ur vidios, on the shorted end why not solder the braid to the 1/2 in stub and connect to the top piece with a bare crimped butt connector and then solder. I also would have used a 1/4 piece of sash cord as a stiffner if need be.. 73 Doug ve3oui
Taping down the item to be soldered; Good Tip!
You can find 2 meter roll-up J-pole antennas made to order here kb3kai.com/j-pole
Thanks
I got a 2m/70cm slimjim that performs better than a J pole from
Joe N9TAX for a great price. www.2wayelectronix.com/main.sc
Hi David, Is this the same design as Ed Fongs DBJ-1?
Not sure. There are several versions of this out there.
I have an ed fong dbj1 and yea I would say it’s the same. And works very well
Dave you could have saved the black plastic ties via using a thin hat pin to allow them to slip off.
Hi Dave. I've got a question that you may be able to help me with. I live in a small rural town and only being a tech, I'm pretty much relegated to the 2 meter bands (I only have a 2 meter radio). Unfortunately, 2 meter seems to be the drunken uncle that no one likes to talk about. 20 meter seems to be the golden child but for a tech, that's out of the question. Most everything that's written about amateur radio seems to be geared for general/extra license holders but not much is done for us poor techs. I guess that maybe it's an encouragement to get to the next level? But what about until you do get to the next level? Also, I'm not as interested in digital, more simplex/repeater use. I'd like to talk to someone that I can meet for a cup of coffee and pick their brain but there doesn't seem to be much of an audience for that. Just curious why that is.
73's,
Jason
Call Sign KM4FPZ
Hi Jason, I looked up your town on the ARRL website and discovered that there are 27 hams in your zip code, several of whom are Techs. You may need to be the evangelist to get some of these folks active. Maybe coming together to put up a local repeater might be a good project. Looks like you're quite a ways away from Birmingham and Montgomery, so hitting a repeater in either could be problematic. The ARRL shows that the closest ARRL-affiliated club is in Alabaster. Hope this helps! 73, Dave
An interesting fact about my area, I'm almost in the geographic center of the state and the EMA has a facility not far from my home. That facility has a repeater and so does the courthouse which is close enough for me to see both from my home and my work. I would think that there would be at least a little traffic on either of these repeaters but in the 2 years I've been licensed, I've never heard a peep on either of them. My main curiosity is about the apparent stigma that UHF and VHF seem to have attached to them. Most advertising is geared towards HF, most articles I've read are about either HF or HF equipment, DX, digital modes, so on and so forth. There isn't much out there for us lowly techies until we get to the next level. I can certainly appreciate that hams are seemingly on a constant drive to eliminate techs by turning them into generals and extras, but I would like to see the community embrace those of us who haven't taken the next step yet. That leads me to my next question, why aren't there more quad band radios out there so that us techies can take advantage of 6 meter, 2 meter and 70cm all in the same radio? is there some sort of reliability issue that comes from packing too much radio into a single chassis?
I'd really like to thank you for taking the time to look up the things you did. That is why you are one of the best TH-camrs out there in any genre. Your advice and information has been invaluable to me and I'm sure to many others as well. That said, keep up the great work.
73's,
Jason
Call Sign KM4FPZ
Ask Dave 43 will directly address your question. I hope it will help. 73, Dave
Ask Dave 43 is now up. Hope it helps. 73, Dave
Nice.
OK, but how does it radiate? :-) Did you get on the air with it?
I've got one of the Ed Fong 2/70 J-poles (edsantennas.weebly.com/) and I have to say I'm quite pleased with it. It's mounted in a PVC pipe shroud on the eave of my house and it works great.
and here i was thinking you are going to make an antenna with your own material and not the bought kit :/
How can I get 42
× =42
I took the dimensions from the instructions.
27 inches ? 12 inches is equal to a Foot or 30cm
That 27 inches you have cut is smaller than 2 feet,,, how does thta work?
Obviously I got something mixed up. Good catch!
Tuning a jpole is pain in the a** :)
boy Dave that was painful
Heat shrink is way too big lol
Ironically what I am seeing is nothing more than a parroting of Ed Fongs J pole antenna. (Check it out) It has the 300 ohm twin and the rg174.
You could totally have re-used the zip-ties. lol
I just found you again, the bell was un-checked hmmm!!!
JPole? Nahhhhh slim jim!
A slim jim has more gain
Hmmm...not so sure.
Not according to Dr Ed Fong who thoroughly studied them both (AND designed the original version of the twin lead one 'OG made.)
After J-STD solder cert these videos always make me cringe. Lol
Go to the doctor and check your lungs.
He keeps telling me to eat less and exercise more.
Nice video....get some damn exercise, you were panting like a long distance runner that just finished a 12k race and all you did was cut a wire.
The video was made quite some time ago. I've since gone through quite a few lung workups. I've been diagnosed with chronic asthma. I've lost 30 pounds and have been exercising and dieting. I'm feeling much better. But the shortness of breath still persists.
@@davecasler Glad to hear! Keep up the good work!