I wanted a cheap decent 70cm Antenna that I can put on the stink pipe on the roof without the neighbors noticing another antenna. I the copper J-pole and thought it would be a great idea. After finding out the parts I need I went to home depot then radio shack and after $15, I had what I needed to make 2 antennas (already had elbows and Tee’s). Cutting and assembly was easy up until I tried to mount a SO-239 connector and solder the center. I have a blow torch and a pencil iron. Nothing in-between so I had a hell of a time getting the solder to stick.
Here is a picture
It took a bit to tune. I thought I needed to be much lower for 440Mhz but I guess I was wrong. I’m getting 1.1 to 1.5 throughout the 70cm band. I hooked it up to HT and with the antenna perched on my desk I was able to work repeaters that I’ve couldn’t with just the HT and it’s antenna. So far impressed. I might paint it black to blend in with the vent pipe on my roof.
I also got ideas to improve the J-pole by fabricating a mount that I I will be able to rivet and solder on the SO-239 connector and also solder it to the pipe with ease.
Now I want to try 146mhz, dual band (144/440) and possibly a 6 meter. I have enough material to make one more UHF antenna.
I’ve constructed a 144/440 Dual band Open Stub J-Pole Antenna.
I saw the plans for this on the internet (link to plans) by Allen Lowe (N0IMW). Since I had a Metal Fabrication background, I thought this would be an easy build.
I understand that everyone else in the world uses Metric, You can convert these numbers to MM and use 10mm aluminum rod and thread for the elements.
However I am not sure about the SO-239 adapter. I’ve read that it can be difficult to obtain the adapter in Europe. Any EU/Metric users, please help me out and give me details on what you did.
(Update 12/2018) Radio-Shack has since closed and the SO-239 adapter I listed on my blueprints are no longer in stock. You can find equivalents on ebay, amazon and other amateur radio or CB supply shops. It’s known as a “SO-239 to 3/8″-24 Adapter”. There are some variants so please make sure it appears the same as the one in my blueprint. You will need to check the diameter of shoulder on the insulation washer and adjust the size of the large to to make sure it fits.
Here is a Step-By-Step video with me stammering on. Getting a little bit better every time I make a video.
I did some minor changes from the above. Instead of using nuts I used pressed “PEM” nut on the underside and used thread protecting vinyl caps on the tips
It was a really fun and quick build. Plus it works okay. It’s no Diamond X510. What else do you expect for around $20 in parts? I love it.
If for whatever reason you can not build this. It is manufactured by the designer of this antenna and has them for sale on his website for a reasonable price. So check out ARROWANTENNAS.COM for the OSJ and other quality crafted antennas.
Due to many e-mails, I just want to state that I do not and will not manufacture these antennas for sale. I think those sold at Arrow Antennas are well worth price.
Antenna Gain, Pattern and NEC data
Some people were curious as to what the gain and pattern is of this antenna is. Arrow Antenna basically said they weren’t posting figures as competitors use gain as a marketing ploy and inflate numbers. However they did publish the patterns. I’ve tried to model the antenna in 4NEC2 without much luck. What I was inputting into NEC was nothing near comparable to what I and some others have measured. Thankfully I wasn’t the only one who was having issues modeling a J-Pole. C Bronson Crothers (AA1ZB) has talked about modeling the J-Pole and wrote quite a bit about it. Carol Milazzo (KP4MD) took it a step further and modeled the Open stub J-pole.
She modeled the antenna in various situations (mounted to mast, free space, free space with ground) and even published the NEC files for all to see. I’d strongly suggest to check out her website for the NEC files and other information that has helped me along in the hobby.
I took the files and messed around to see what happens.
Depending on the height about ground, your looking at anywhere between 3-7dBi (or .85dbd-4.85dBd) gain according to NEC Data. In the perfect world, if that antenna was fed with 50 watts, it would effectively radiate anywhere from 60 to 150watts. But that is in the perfect world which we are not in. Things like the type and length of coax used, connectors used, nearby structures, type of ground and a bunch of many other variables factor into how well an antenna performs.
In the antenna gain world you will see dBi and dBd depending on the manufacturer. You just don’t measure Decibels. In this case it’s used as a reference against either an isotropic antenna (dBi) or against a dipole (dBd). So if you see antenna readings in dBi, it’s in reference to a theoretical perfect antenna that radiates evenly in every direction. If you see dBd, the antenna is being compared against a half-wave dipole antenna. The difference between dBi and dBd is 2.15. dBd is comparison against an actual antenna. Some hams confuse dBi and dBd and some manufacturers confuse the buyer by not telling you the reference (It has 9dB of gain!!). Most manufacturers use dBi as it’s a bigger looking number. Just subtract 2.15 and you will know the gain compared to a half-wave dipole.
I bring up dBi vs. dBd gain for the reasons why Arrow Antenna doesn’t want to talk about it. An antenna shouldn’t be just about gain. It should factor in your shopping but you honestly won’t really know how an antenna will perform until you get it in the at. There are times I hear that the J-pole is no different than a dipole or even a ground plane which is not true. This particular antenna has some gain. It’s not as high when compared to the claims of large scale antenna manufacturers but considering the materials used, ease of assembly and use, I think this is a really good antenna. Okay, now that I am done ranting… let’s look at the pattern
This is a 3-d wireframe of the pattern (in gray) with an outline of the vertical polarization. The antenna is pretty much Omni-directional Horizontally. Vertically, the focus of energy is between 15 and 85 degrees. It would be ideal to mount the antenna above the roof line or at least 10ft off the ground as the signal radiates more from the side. This antenna wouldn’t really be ideal for Sat use as there is a huge null and less gain when looking towards the sky.
SWR and analyzer results
SWR plays an important role as well. If the antenna is not correct, some of the power sent to the antenna will come back to the radio. Modern rigs can see this and if too much power is coming back, the rig will step down in power to prevent damage to the finals. This usually happens if the SWR is above 2:1 or 3:1 depending on the rig. We need to get the SWR of this antenna down to 1:0 as possible. If this antenna is fabricated and assembled correctly, there should be little concern about SWR but it’s safe to make sure and check before using or even installing it
Here is what 4NEC2 Predicted On the VHF Side. By looking at the blue line towards the top of the image, you will see that it has excellent SWR throughout the 2M band. Looking at the green line, you will see that the impedance is also decent.
The UHF Side of the antenna doesn’t look so great when compared to the VHF side of the antenna. But it’s still useable. Once again these are predictions from the software. It’s doesn’t mean that’s how the antenna is going to exactly perform. But it will give you an idea of what’s going to happen. Let’s do some real measurements.
Someone let me borrow their Antenna Analyzer a few years back. You will see at 145.98Mhz I got a reading of 1.0SWR with a 51ohm impedance. The antenna was resting on a wooden chair so I am not sure what the value would be when fully installed but I don’t think it would change that much since it doesn’t need grounding. But coupling to nearby fixtures
After making various antennas, I felt I needed some kind of analyzer of my own. I purchased a mRS MiniVNA PRO. It covers HF/VHF only but it give me a better idea of how the antenna is performing throughout the band.
Here is a plot of the antenna installed. You will see that the antenna is usable from 135MHz to around 155MHz. It’s a nice wide band antenna and you will see how it differs from what 4NEC2 Predicted. But it’s not far off
Thanks to Jon (KI6RT), he provided some SWR plots from the VNA. What’s great is that he measured the UHF side of the antenna which I’m un-able to measure with the equipment I have. According to Jon, this was measure with the antenna installed at height
Even though I did not design this antenna, I often get e-mails from people who had trouble with this particular antenna. I helped troubleshoot a lot of the issues and found out that the majority of problems were in result of the person not following the instructions as listed on either my or Mr. Lowe’s prints. Most common mistakes were people cutting the lengths short or people substituting the materials called with others. For those living in the rest of the world, I know you might have trouble trying to find SAE/Imperial material and will substitute 3/8″ with 10mm rod and hardware. I am not sure if they make a Metric SO-239 to 10MM adapter. But I’ve heard from multiple people that it work with 10mm.
Another common mistake is when it comes to testing. Testing should be done with the antenna installed or at least mounted to a pole to simulate an installation. Some people were laying the antenna on the ground, holding it with their hand or placing it against large metallic items (like a car) which will produce different readings. You won’t know how it performs SWR wise until you have it installed. Even though it’s rare, be prepared to install and remove the antenna multiple times while taking readings.
There is an issue which I haven’t touched on. Much care should be taken to prevent water from getting into the threads of the SO-239 adapter or in the adapter itself. Even more so if you live in colder climates where water can freeze and expand.
If you are unsure about cutting the elements to the proper length, it’s best to cut it a little longer and grind or re-cut the elements. It’s better to have elements that are too long instead of being too short. If you happened to cut it too short, it’s possible to use a coupler to adjust the length of the antenna but I would suggest re-making the element in question.
Others who built the OSJ-Pole
I like when people send me their creations. Some follow instructions exactly while others are creative and use what they have to make a working antenna. Here are some links to those who also made the antenna. Maybe they can provide some insight into things I forgot.
F6FZU’s OSJ-Pole – French reader who managed to make the antenna using metric tubing as well as different materials while getting decent results on the analyzer. The one thing that stands out is that the angle he using to mount the elements is made from Galvanized dipped steal. I would avoid using steel at all costs. It appears he is taking steps to weather proof the steel.
Michigan Amateur Radio Alliance (MARA) – Couple of their club members (KD8PVS & KD8UCP) decided to build the OSJ-Pole using my prints. They did a very nice job and they also found another source for the vinyl caps and provided clamping and installation photos of their antenna. Nice job!
KI6RT’s QRZ.com Profile – In Jon’s profile, he built the OSJ-Pole. He manged to run the antenna through a high end analyzer showing SWR results of both the VHF and UHF portions of the antenna. It shows that at least the SWR is decent in both the bands.
I found my small camera and Had some pictures of when I built my G5RV.
This is the center insulator of my G5RV. I designed this using Autocad so it can used as a diople or inverted “V”. I will post the DXF later on if there is any interest.
I had a piece of Lexan (Plexiglass). I was cut using a CNC 4000w laser. I know many people do not have access to a cutting laser so I saw and drill press will do just as well. I then heated the edges with a blow torch just to clean up the piece and get rid of any sharp corners.
Here is the G5RV Half done. I used 12ga stranded 300ohm twin lead wire. I prefer stranded wire even though it cost a little more than the solid cord. After whipping around in the wind I would be afraid that the solid core would break in places and render the antenna useless. I also used 12ga stranded wire for the antenna. I managed to get 500ft of it but it was insulated so I spent a couple of hours stripping 100+ ft of copper wire.
I know it’s hard to make out but it’s done and in the tree. I was using a g5rv jr. kit that I bought before and this antenna took up the entire length from my house to the tree with a couple of inches to spare. It’s 40 ft high up and after months and hundreds of contacts later. It’s still performing well.
As I’ve been mostly getting European and South American DX contacts, I’ve been hoping to get some Asian, African or Australian contacts. Today I finally made contact with ZS2DK (Mitch, Port Elizabeth SA) on 20M PSK31. I was excited and he had a very legible copy. I decided to look it up on PSK Reporter and I saw that there was another SA station using JT65 on 40m so I figured to give it a try. Sure enough I made contact with ZS1LS (Allen, Cape Town SA) on 14.076 using JT65.
Not Too bad.
Jeffrey Bail – N1BMX
P.O. Box 484
W. Springfield MA, 01090-0484
When I first purchased a P.O. box using USPS online in January 2010. I went to my local post office and they assigned me Box 722. They gave me a key and made sure that the box worked. I changed my address with the FCC and a lot of other places to my new box so I can avoid stuff being sent to my home. I got some mail every once in awhile and I thought it was ok. Last weekend I went to check my mail and notice that someone else’s mail was in the box address to 722. I took the mail to the counter and the lady told me that my box was really 484 and that the box has been overflowing with mail. I was never aware or made aware of that my box has been re-assigned and I never knew that my mail was going to this new mystery box. I guess that this took place in February because I purchased a size 2 box and they assigned me a size 1 box.
In that mail I received some QSL cards from KD8FIP (Frank) JT65, KD8FKD (Len) CW contact, KD0JHW (Bill) PSK31 and KG4AZN (Chris) Feld Hell. Thank you guys for the cards and when I get my printed you’ll be the first reply.
Started off the morning on 20m JT65 (14.076.00Mhz). I noticed there were people talking so I jumped in. Managed to get only two contacts with F8RZ (Jean, France) and N9GUE (Fred, US).
Later on in the evening I tried WSPR. Never heard about it until this morning while exploring PSK Reporter. What’s funny is that I confused it with a local spanish speaking AM radio station WSPR. After doing some reading about it and installing the Software. I let it sit for an hour on 30M and then TX my call a couple of time. I was amazed at who heard my signal.
I like this. It shows far your signal can reach. Granted the mode is designed for Long distance. I am going to try it again with only 5 watts.
While messing around with WSPR I kept hearing a digital mode that I never heard before. The person sent out an RSID using Ham Radio Deluxe stating it was a Olivia signal.
I made contact with VE7NBQ (Peter, VANCOUVER, BC) and Rag chew for a tiny bit.
After that I wanted to exercise my lungs and do some voice contacts. I heard KH7Y (Fred, HI) with a pileup of people trying to get him. After about 10min of throwing my call I finally got him. I hope he confirms through e-qsl and/or lotw because I don’t often hear Hawaii and by the pileup of people I don’t think they do either. A new state for the hunt of WAS.
I also heard HI8ROD (Rodrigo, Dominican Republic) and made contact with him quite easily.
I had to take down the G5RV dipole as I was hosting a party at my house. It would have been in the way and I didn’t want the kids to be messing around with it.
When I first put up the dipole I could not get my ladder high enough up so my Dipole was at an angle. Since I was tinkering around with the antenna I manage to get it much higher. I am pleased with the results.
Now that my antenna is back up and had some spare time , I went on and made a lot of contacts. I also took part in the IARU Region I Field Day with only 16 contacts.
On PSK I manage to get my first contact with Saudi Arabia. His call was HZ1EA (emad) and he was running QRP @ 5 Watts. Also worked Serbia for my first time with YU7AU.
I also tried PSK on 30m (10.140.ooMhz) for the first time. I got work UU7JC, CO8LY and WB8TDG. WB8TDG was using RTTYM 8/500 which I never used untill tonight.
Overall very good night. Now I have to learn to submit contest logs.
Ever since I got licensed I always wanted to try Satellite Communications. So after looking through one of my favorite websites (HackADay.Com) I saw an article on how to build a Yagi antenna using some screws pvc pipe and aluminum arrows. This peaked my interest in Satellite communications. I’ve been aware of the commerical antennas built for this purpose and I am also aware of some of the DIY antennas. All I have for a radio is a handheld Kenwood TH-78A that I will be using and I plan on mounting the antenna on a old tripod.
Hopefully I can have this built before my daughter arrives. But either way it’s going to be a fun simple project.
While my parts for my CW keyer are out for paint all I had to play with is the plexiglass base of the keyer.
I managed to get it working and I went on 7.040.50Mhz (40m) and started sending CQ TEST. All of a sudden I hear “-. .—- -… — -..- -.. . -.- -… —.. ..-. . (N1BMX DE KB8FE)” I was happy because instead of using software to decode morse I did it by pen and paper. He was sending slow enough for me to understand even though I was sending much faster and messing up a lot. His call is KB8FE (Keith, OH). He asked me about my station and then told me to keep practicing CW. So I am please to make a contact and it makes me want to master CW now.
I’ve been noticing that I have been practicing CW more than I have been doing any other mode.