in Experiment, Gear, Magic, Research, Spectral Arts

Homebrew 1/2 Wavelength 2m J-Pole Antenna Build – Part 1 of 2

Building my +5 Staff of Summoning

My Nagoya whip apparently does not cut it with my Baofeng UV-5R. I’m not even sure I’m hitting the repeater, though it’s on a mountain that I can see across the river. I have no elmer to really help me figure it out.

Plus I bought the cheap radio all the more experienced hams told me not to. The Baofeng. One of the “non-compliant Chinese” radios, which a Toronto area radio shop told me they do not carry any accessories for. So many sources told me not to buy this, but I effectively tuned them out. And now I’m not able to tune anybody in to talk.

Okay, I got lost in my own metaphor there. I can hear others talking, but all my attempts to raise somebody, whether on simplex, repeater or on a net check-in have failed. I’m shy, but I’ve put myself out there again and again with no response (okay, except once in a dream, but that’s another story…).

I’m not ready to plop down money on a new transceiver though. And WI5HER claims that it’s “all about the antenna”. Don’t get me wrong, other people seem to have adequate success with their Baofengs. May depend on environment and proximity and density of other users. But where I’m trying to ‘work’ the airwaves, it’s not doing it with the little Nagoya (which is already bigger than the rubber duck it comes with).

So one of the major next steps that is affordable for people in my situation: you have a Baofeng and it’s not seemingly strong enough to reach other people, is to buy or build a J-Pole antenna for 2m.

If you’re not in the club already, two meters is the wave-length of the frequency band we know as 144-148 mHz FM. In the commercial radio spectrum in the US and Canada at least we listen between around 80-108 mHz FM. We usually call that just like 100.3 FM, but the true measurement is megahertz, or as they used to call it back in like the 50s and before (I don’t know when it changed tbh) “megacycles.” 1 hertz is one cycle per second. 1 megahertz is one million times that. Whatever that even means. Here’s a good diagram to help you sort it out in your head.

Anyway the model I followed was basically this guy:

And I even emailed him with questions and he was kind enough to answer (though someone else later gave a reason to do something different).

The measurements I used were based off this j pole calculator.

Best technical explanation I’ve seen of what’s happening (without being too dense) is this video:

I like that there is kind of a trombone quality about these antennas.

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I don’t think it’s accidental if we break both these devices down to what they’re doing: enabling the user to transmit a signal at a particular wavelength. One in audio (Hz) and one in radio (mHz). You can explore these feelings more on Wikipedia’s trombone page if you’re so inclined.

Also check out the J-Pole Antenna site. He has a guide for especially Baofengers about using external antennas on your radio, the why and more importantly the how. The guy’s in the US and makes and ships finished versions of what I’ve built below of much higher quality than what I will embark herein to show you now. I submit with humility, knowing the quality of my soldering is quite “shitty”, but this is my first time working with these materials (copper, flux, solder) and these tools really – mainly a blowtorch used in this way.

Best way to get good at something is to experiment, iterate, ask questions, try it out. Then you can do it better later. Sometimes you can succeed on a first try though too.

Jury’s still out on that for me, as I’m awaiting my coaxial cable which will let me mount and link the antenna to the radio.

This is after completing the cutting and soldering of the copper 1/2″ pipe to the measurements on the j-pole calculator.

I never cut copper pipe before. I bought a little $5 pipe cutter, which worked but crappily. This video was useful for general principle:

I also experienced a bug in my process because I bought two wrong parts: over-sized end caps, and an elbow which was 1/2″ on one end, but not on the other. So I bought a straight coupler and used that to join the small end of the elbow to the short arm (1/4 wavelength). There was no issue with that–the two arms are straight and parallel.

 

 

 

I tried to rotate this image, but oh well. This is the copper tubing attached with u-bolts to a stick of wood I will use as a mast and attach to the outer peak of my shed. It’s definitely starting to look like some kind of wizard LARP staff, which I really like.

Maybe I will get a costume to go with it.

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Or maybe I can reserve that for when I actually get good at this.

Here is my electrical connection. I bought the SO-239 connector from Durham Radio, outside Toronto (online). Unlike the radio store that told me they don’t deal with my ‘non-compliant’ Chinese radio, Durham actually – you know – sold me radio parts. Go figure!

[Insider tip: you didn’t hear it from me, but they *might* even sell you an Android TV box, which is sketchy af but I like it! Netflix Canada subscribers, you feel my pain!]

Yes, I know my welds are ugly af, but again, first time so cut me some slack. They are sealed, which is mainly what’s important to me rn. On the feedpoint connection, I used electrical solder which I got from the hardware store rather than the plumbing solder I used everywhere else.

Oh, if you don’t know how to solder onto copper, you should take a look at least at this video. It’s really not complicated:

But I guess you can’t pull it off with just a soldering iron, cause you need to actually get the copper really hot (and apply flux first) or else your solder won’t ever really bond. I know because I tried to connect the stripped piece of copper wire I picked up after an electrician did a small wiring job at our house to the back of the SO-239 aka UHF female jack.

Anyway so I did eventually use the torch on it and that worked.

But there’s a pretty big “gotcha” here in this process, because it’s highly likely that you will melt the plastic inner on the UHF female. You can sorta see it poorly in the photo above, the white part is partially melted.

Once I get my coax, I will see how well the PL-259 seats into that. Worst case scenario (I hope) is I heat up a knife and cut out the melt that interferes – if any.

If I had it to do all over again, I would get a smaller or hand-held or ‘micro’ torch and use something which I could more easily control. I already had one like this, a sort of fat big propane canister with a simple control at top. It’s fine for general use, but for a controlled application of heat like this, something smaller would definitely be in order.

Oh well, I will take my lumps as part of the learning process.

Now, in the J-Pole build video above, he uses a flat copper plate to connect his UHF female to the copper pipe. It was non-obvious to me IRL where/how I could acquire such a flat piece of copper.

So what I did ultimately was flatten down one of the too-big copper end caps I had bought with a hammer and very small anvil that I have. Then I used a corded drill, a lot of patience and a little swearing to drill and bore out larger and larger an adequately sized hole to pass the UHF female jack through and connect the nut on it.

I know my results are crappy looking, but I’m proud regardless for a first try. You always encounter problems in building something totally new with new materials and tools, and it’s all about how you improvise in the moment to achieve at least an approximation of your desired end-goal.

As far as I can tell, this will probably do the job. I did a decent job of staying in line with the measurements the J-Pole calculator gave me. I tuned mine for 146 mHz which is right in the middle of the 2m band. Unfortunately, I don’t yet have an SWR meter – though I found that Durham sells an MFJ (MJF?) that works on 2m for around $60 so I will probably pick that up one day. It’s too expensive to buy into all this radio equipment at once before I even know what I’m doing.

A hobby is all about developing an interest into a mild side-obsession. That takes both time and repeated effort and can’t be just bought into all at once.

I would guess that with everything (excluding the cost of tools, coax and the SMA female to UHF female jumper I had to buy for the Baofeng), the J-Pole antenna build I did probably cost me around $20-25, including the mounting hardware. I didn’t keep exact track.

I ordered about 35 ft of RG58 coax, even though I saw some people say RG8U would be better. I honestly don’t know the difference yet, so this is the price of learning. Maybe I make an imperfect prototype. Worse things could happen. Like doing nothing or giving up completely. Cost me about $35 plus shipping.

SMA female to UHF female from Durham Radio outside Toronto, Canada cost me just under $20 plus shipping, but now I have a radio store that will allow me to indulge my cheap Chinese technology desires – even to my own detriment.

But as I see it, how could a learning experience like this be bad?

Unless, once I get it all mounted, wired and connected up people still can’t hear me.

Then we’ll have a problem.

Even if that happens though, I’ll probably still be left with a perfectly serviceable 2m antenna which I can use with a better radio once I finally decide to throw my Baofeng out the window.

Post script:

For every trash-talking ham out there who will tell you not to buy a Baofeng, most of them are talking from experience because they almost all have one. So take that for whatever it’s worth. In technology, ubiquity counts for a hell of a lot. So if you feel compelled to buy one, don’t let someone stop you if it’s your path to learning more.


Also published on Medium.

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