Tape Measure Yagi Antenna With 3D Printed Couplers

by bekathwia

36K12741

Intro: Tape Measure Yagi Antenna With 3D Printed Couplers

My take on this classic design uses pieces of standard tape measure steel as radials, a 1-inch diameter PVC pipe as the mast, and 3D printed couplers to link the radials to the mast. I built this 2m band antenna to listen to satellites.

STEP 1: 3D Printed Couplers

I modeled the couplers using Tinkercad, first by creating stand-ins for both the mast and the tape measure, then forming solids to join the two and grouping everything together. After making this long version I shortened it so the couplers could be closer together on the mast, and created a few versions for the end cap and driven element couplers. I printed the rainbow of parts on my Creality CR10s-pro using 20% infill. You can copy the design on Tinkercad or download my STL files directly from this step.


Disclosure: at the time of this writing, I'm an employee of Autodesk, which makes Tinkercad.

STEP 2: Assemble the Antenna

I followed 2m band specs I found online for the length and spacing of the tape measure pieces. I'm far from the first person to make one of these, and here are the designs I researched:

The driven element pieces are connected both to each other with a wire folded into a hairpin shape. I sanded off the paint from the tape measure steel where I wanted to solder and connected the driven elements with a piece of wire bent into a hairpin shape as well as the two parts of the coaxial cable.

STEP 3: Hardware & Software Setup

I'm using this software-defined radio USB dongle to connect the antenna to my computer running CubicSDR, a free app that is cross-platform and open source. Inside CubicSDR, I can see a waterfall display of the spectrum and I can move around to look at and listen to different frequencies. If you're new to this setup, play around with the small dipole antenna that comes with the SDR unit first. You can tune to your favorite local FM radio station to start, or try finding your local NOAA weather broadcast station, which will also supply a constant source of audio. Then try to tune to your local repeaters, which will only be visible on the display when they are transmitting, which isn't necessarily all the time.

STEP 4: Trying It Out

Once I got up on the roof I remembered to tape the ends of the cut pieces of tape measure for safety. I used the Heavens Above android app to look up and track satellites with downlinks operating in the 2m band and had a go at pointing the antenna while setting the frequency on the computer. It's hard to do both at the same time so I got some help. We didn't really get any results that first time out, so I borrowed a friend's nanoVNA to try to check and tune the standing wave ratio of my antenna. I first set it to sweep between 144 and 148Mhz, then calibrated it using the included open, short, and load nubbins. I tuned my antenna by adjusting the spacing between the driven elements and the shape of the hairpin wire. We're going for as close to 1 as can be managed here. Back up to the roof to try again.

STEP 5: Partially-Successful Results

The satellites I ended up being able to hear the best were NOAA weather satellites, which transmit an analog picture signal containing satellite images that can be decoded from the recorded audio file. My best attempt so far only had a small area that wasn't static, but you can see with the map overlay and compared to the full satellite image I looked up online, I've got a partial result here. It's so cool that signal came from space! I used noaa-apt software to decode the images.

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30 Comments

alpha1138 3 years ago

Good morning, I have built a couple of these. First problem is they are prone to flopping in a light breeze and useless in a strong wind. Do you have any ideas to strengthen the elements? Second problem is storage. I've been toying with the idea of using a larger pvc pipe with end caps. Very nice write up on the tape measure beam. 73 KA6JMM Rick

BobDakotanBRJ 2 years ago

You could try using 2 layers of tape measure with the curves in opposite directions. That might make the arms rigid enough to take the breeze from either direction. You would need to construct some more little brackets to hold the ends together
Or you could just try to position the antenna so the breeze is pushing the arms straight instead of curling them up--might be your easiest solution.
For an all weather design you could use angle-iron shaped pieces for the arms (probably aluminum would make sense) and use a big enough pipe to nest all the pieces inside for storage. Since I don't have a 3-d printer I'd just use pvc x fittings for brackets and attach the arms with a set screw. Or you could find 3 pieces of pipe that fit one inside the other. (EMT conduit comes to my mind, 1/2, 3/4 and 1 inch sizes, and it would all fit in a 1-1/4 inch PVC pipe for the center staff piece. Go with schedule 80 pvc conduit for extra toughness.). Have fun!

JohnW51 2 years ago

Just glue the tape measure sections to pieces of PVC.

Gomez Addams 3 years ago

why would PVC pipe flop about in the breeze? Are you using glue?

jimvandamme 2 years ago

The elements flop around. If you can deal with that, you can store the antenna by wrapping the elements around until it looks like a stick, wrapping each with a tie wire, then putting it in a bag or bigger pipe.

If you can't deal with the rigidity problem, make antennas the old-fashioned way, with rigid tubing elements. Of course it needs a plane to store it against (wall or ceiling) but the hard part is transporting it.

ELECTRONFLYER1 3 years ago

SEEMS LIKE A BETTER CONDUCTING MATERIAL THAN STEEL WOULD WORK BETTER BUT WHAT DO I KNOW.

JohnW51 2 years ago

Aluminum, but you can't solder to it. Aluminum tubing is available in most home improvement stores. But it would be cheaper just to buy a yagi antenna, assuming you could get one tuned to the proper wavelength.

jimvandamme 2 years ago

Yes, you could pick up a dB or 2 by using solid gold rod. it would have to be the same width as the tape or the bandwidth would suffer.

JohnW51 2 years ago

Interesting. So, would this work for broadcast TV? Seems like it would. I have simple (commercially built) yagi antenna in my attic, which I installed before cable provided acceptable reception in my area. (My neighbors that had cable TV would marvel at the picture quality and ask how I got such a great picture. LOL!) I think I could measure the elements and placement on that antenna and transfer them to your cool design. It would be an interesting experiment.

mcshrade 2 years ago

That is a very good little SDR! And the Amazon price is a few dollars less than on the Noo Elec website. It has an always on bias tee putting out 4.5 volts to power a wide band or frequency specific rf amplifier to help boost your reception.

AlexanderS290 3 years ago

the RTL dongle variants are numerous. the metal shielded one are expected to be the higher grade designs with maybe a bit better selection for parts and pcb design. thus better signal to noise ratio and a more stable frequency should be expected - but thats not a final promise just by seeing the outside.

if you order something like that it will be compatible with most if not all SDR type software. (and i dont give you a recommendation because its often personal preference what to use.) the option to use "virtual audio cables" or even real ones or audio recordings to feed those data into sub-programs for special decoding purposes is a thing mentioned in the presentation as well - so dont miss it.

PS: dont forget to order a RF cable that matches your receiver dongle at one end. the other will be anyways cut off as you can see in the video. (i am not sure if it would make sense to give the antenna a socket on its own but it should be a not to bad and feasible option.)

K1YBE 3 years ago

Becky.. We've been building this antenna the hard way for years and your concept will become a project for our Ham club. After assembling and testing the parts I just printed, we might suggest some tweaks. Prior to seeing your design were experimenting with a version that allows adjusting the element spacings to achieve different antenna patterns and your method should greatly simply that design. I am also a big fan of TinkerCad circuits and have used it in a number of STEM events. So happy you did this.

bekathwia 3 years ago

That's great to hear! Let me know how it goes!

Gomez Addams 3 years ago

Just a tip: the stub matching element to match the balanced antenna to the unbalance coaxial feedline will work, but you may find you get better performance with a home-made simple balun. Be sure to find the correct ferrite number for the frequency band of interest. Baluns are a fun and easy project and the parts are cheap. You can build one in an afternoon. Also, for weather satellites which often have circular polarization, you might try a simple "quadrifilar" antenna. Have fun! KG0MEZ

Sigma Toot 3 years ago

Hi Becky
What an inspirational concept! At the tender age of 66, I've still got the same enthusiasm for technology as when I took my first b&w 405-line TV to bits ... this sort of project is *exactly* what's needed to encourage more uptake in STEM.
Fantastic! - keep up the good work.

PS - my user name alludes to my garage i.e. 'Sigma' (the sum of) plus 'Toot' - a weird North of England word that my wife uses to describe all those 'interesting & potentially useful' things I hoard (and which most other people would throw away) šŸ˜„šŸ‘

Sawadeee 3 years ago

Great job. Been ham since 1964. Happy to see smart young people learning and enjoying this hobby. I see an engineer in the making...
PS. Narrators voice was perfect.

ANDRELAS 3 years ago

Maybe short pigeon French for tout le monde.

mcshrade 3 years ago

That last group of signals was upper sideband voice. You were in AM or possibly FM when
you should have been in USB. Those signals were actually very good considering they were from space, so the antenna is working quite well!
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