Introduction: The Tape Measure Antenna

Are you looking for an easy kid friendly project? Are you looking for a project to encourage a new generation of ham radio operators?

This project is unusual, so it’s something that will certainly capture the attention of anyone, particularly a kid. It’s an antenna built out of PVC pipe, a tape measure and a handful of hose clamps.

This antenna is designed for two-meter operations, which, for a newbie ham operator, is one of the bands available under the Technician license in the US. Plus it’s easy to build and gives a great opportunity to teach several subjects with a hands-on approach.

Disclaimer: This project isn’t new; it’s not even my idea or design. I used the design from Joe Leggios (WB2HOL). The plans to his antenna are here.

Project Background

My nephew recently expressed interest in earning his Technician class amateur radio license. While some people discount the Technician level license of amateur radio as “ridiculously simple”  (including a well known conservative talk radio personality) it’s not so easy for an eight-year old. It requires comprehension of concepts that they still have yet to cover in school. Topics like basic algebra and principals of electricity.

When I set out to find a project, I was looking for something unusual that would grab his attention but something that was easy, fast and required few tools or skills. And I wanted it to be cheap. There is a total of $20 in materials in this antenna, assuming everything is purchased specifically for this project and not scavenged or salvaged parts.

The fundamentals of antennas is the one area I’ve been finding difficult to teach my nephew. Mostly because I refuse to “teach the test”. I want him to fully understand the material, not just pass a test. And I have found that I have had to teach him basic algebra in the process.

This project was perfect as I could scale it up or down as a lesson in a number of ways. Which is to say you can use the plans to build a perfectly workable antenna, or, you can use the formula for a Yagi antenna to modify the design. In my case, my nephew and I used the plans from WB2HOL, but we worked through the math to come up with element lengths.

And, in the end, we built something useable for when he earns his Technician class license.

Materials List

3/4” Schedule 40 PVC Pipe - at least 25”
6 hose clams big enough to fit around the PVC pipe
1 3/4” PVC tee
2 3/4” PVC crosses
8’ RG-58 cable with a connector attached to one side. I soldered a female BNC to mine.
5” wire. I used 18 gauge solid copper wire, but I’m told anything works.
Rosin core solder
Tape measure with 1” wide tape
PVC glue

Tools Needed

Soldering iron
Tape measure
Pipe cutters
Wire stripper
Shears or scissors
Sand paper
SWR Meter
Screwdriver or wrench for tightening the hose clamps

Step 1: Cutting the Elements and Assembling the Boom

You’ll need to cut two pieces of PVC pipe. One piece will be 17 1/2”. The other 7”. This, along with the PVC connectors, will form the frame of the antenna.

Assemble the pipe to form the frame ("boom") of the antenna. Gluing each piece together, the 17 1/2” piece connects between the tee and the first cross. The PVC tee is the front of the antenna. The 7” piece connects between the first and second tees.

Disassemble the tape measure by pulling the tape out of the case. If you pull the tape past it’s end, you’ll find that it’s connected to a spring. Simply twist the tape so it disconnects from the spring.

Cut the tape at 35 1/8”. This will be the director of the antenna and will attach to the front of the antenna.

Cut two 17 3/4” long pieces of the tape. These will serve as the driven elements.


Cut an additional element from the tape. This will need to be 41 3/8”. This is the reflector element.

Sand all the ends of the elements so they are smooth to the touch. These are extremely sharp if left un-sanded. Also sand off about 1/2” of paint on the ends of the bottom side of the driven elements. This will be where you will solder the wires later.

Note: If you are going to mount the antenna, set it up so the antenna will be forward of the mounts. Yagi antennas may suffer in performance if mounted elsewhere, like the center of the boom.

Step 2: Installing the Elements of the Antenna

Slip the hose clams over the PVC tee at the front and slip the Director element under it. Tighten the hose clams so it is secure.

Attach each of the driven elements to the frame of the antenna with the sanded sides facing each other. Before securing the elements, space the elements 1” apart and tighten the clamps.

Finally, attach the reflector element at the rear of the antenna and tighten the clamps.

Step 3: Soldering the Wires

Now you will tin the ends of the driven element. Simply heat the soldering iron and apply solder to the tape measure at the sanded spots. Make small pads where you can solder two wires to each side of each driven element.

Strip the end of the RG-58 cable and isolate the outer and inner wire. Solder one side of the RG-58 to a driven element and the other to the opposite driven element.

Strip the 5” piece of 18 gauge (or whatever wire you have) and solder a side to each of the driven elements.

I chose to add an optional piece of PVC and an elbow at the rear of the antenna to make it easier to hold and/or mount. I also chose not to glue the PVC together so the antenna can be broken down for storage.

Step 4: Adjusting the Antenna

Adjusting the antenna is very simple. Simply attach a SWR meter between the antenna and the radio. Adjust your radio to 146.580 mhz and check your SWR reading. If the reading is more than 1.2 to 1, turn off your radio and adjust the driven elements by loosening the hose clams and moving the elements toward each other. Turn on your radio and check your SWR again. Repeat until your SWR is at an acceptable level. I was lucky and my antenna registered extremely close to 1 to 1 without adjustment.

When adjusting the driven elements make sure your radio is off.


Step 5: Technical Notes

Software modeling programs show that this antenna should have a gain of 7.3 dBd.

Real world experience: Running a HT at 5 watts, my nephew and I were able to use a repeater 65.7 miles away, with reports of a clear signal. We were also able to access several other repeaters that are 40 to 50-miles away. Performance will vary based on your location. 

While this antenna is designed for VHF two-meter operations, it can easily be redesigned for other frequencies like 1.25 meter, 70 cm or 33 cm. There are many websites that will calculate the length of and length between the elements on a Yagi-Uda antenna. You can try Martin Meserve's (K7MEM) online calculator here


Additional information on this antenna

The original plans for this antenna are available at Joe Leggios (WB2HOL) website. A link to the plans is here.

Additional plans are available from KC0TKS' website here, as well as from NT1K's website here.


Comments

author
Neutronned made it!(author)2016-08-26

I really liked this project idea and made one myself from PVC pipe. It worked so well I decided to invest some time into making it slimmer and lighter using 3D printed supports and a fiber glass rod. See the pictures below of final antenna.

The tape measure sections are held to the printed supports using VHB (very high bond) double-stick tape. All three supports are identical and slide on 5/16" fiber glass rod. After positioning the supports on the rod, I put some super glue at the junction between the rod and support. I also made a pistol grip that clamps onto the rear rod section.

You can find the 3D parts on Tinkercad - search for "yagi" and look for "Yagi Grip A" "Yagi Grip B" and "Yagi Antenna Support". If you have suggestions for improvements, please let me know.

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DannyM111 made it!(author)2016-09-07

On the director support, I see there is a blue piece on top of the tape measure but I do not see that in your 3d support on Tinkercad. Can you clarify for me?

Danny

W4ZAP

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SandyM77 made it!(author)2016-06-07

How do you attach the coax cable to the elements? Do you use the metallic shielding that has been twisted into 2 strands? YOu are not showing a connector in the picture.

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jcoman made it!(author)2016-06-07

You sand off a section on the driven element, flux it and tin it with solder. You seperate the conductor and outer stranded shielding, making them into a Y shape ( being careful to not let them touch eachother) and solder them to the areas you just cleaned and soldered.

author
KevinI made it!(author)2016-05-06

I'm surprised there has been no mention of the huge mistake in the text here versus the correct text in the original plans! The first piece of PVC pipe must be cut to 11 1/2 inches, NOT 17 1/2 inches, as written. You should have seen the looks on all the faces when I had to tell a room full of people that their glued-in pipe was the wrong length at our antenna building session! Luckily, I caught it in time when I looked around the room and saw all the weirdly shaped frames! We build twenty of them and they all worked great!

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frolen13 made it!(author)2016-04-23

Would this work as a good fm radio antenna?

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jcoman made it!(author)2016-04-24

Yes, but you need to make some modifications to improve its gain. It's tuned for the amateur band so you need to cut the elements for the FM band to optimize the recieve. It will work good as-is on recieve but, if you are looking to build the highest gain antenna you can, you should build it with shorter elements. Your driven element should be around 57.25", your reflector element should be 58.125" and 53.125".

Remember that its a directional antenna, so you will only recieve stations pretty much in the direction its pointed.

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Braden+T made it!(author)2016-04-23

I need to know if I could use something like this on a cubesat

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jcoman made it!(author)2016-04-23

Sure, lots of people do.

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CountParadox made it!(author)2015-12-28

I decided to make one of these, I love in Australia, and to buy everything needed it has cost me a total of $80-90AU ($50-60US?)

I hate how expensive simple stuff is in this country ;_;

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KK4Z made it!(author)2015-12-10

Mr. Coman, Great post! My question is, does it matter what the length of the feed line is? I am using 8x and thinking of about 10’ not counting the choke wrapped around the mast. I would very much appreciate your wisdom on this. Thanks! Scott KW4JM

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jcoman made it!(author)2015-12-10

The length doesn't matter on the coax. I used 8 feet just because its what I had handy at the time. There is so little attenuation in two feet of feedline that you'll never notice it.

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KK4Z made it!(author)2015-12-11

Thanks. Helpful again.

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psantos-1 made it!(author)2015-04-22

Hello, jcomen. I have been searching for a way to "redirect" 3G cellphone frequencies from the outside into my room both for my cellphone and my internet pendrive. I work on hydro-power projects far away from any towns and inhabit a (pretty good) housing container for most of the year. The thing is that both outer and inner walls are made of metal sheets and everything is grounded because of the electrical instalation and lightning protection, almost making my room a perfect Faraday cage ! I was thinking of building an outdoor "receiving" antenna and running a small lenght of coax cable to a "broadcasting" antenna inside the room without using any sort of power, a passive device.

Since this sort of knowledge is way off my league can you help me with any ideas ?

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HammE made it!(author)2015-01-11

Have you tried contacting a satellite, or the ISS? I would like to know to see if I could build one of these so I could try contacting NA1SS (the American part of the ISS.)

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MrSquare made it!(author)2014-10-18

My first homebrew antenna and my first Instructable build. Super easy and fun to build! Tested it out on a Baofeng UV-5RAX handheld and was able to pick up a friend on the same model radio about 6 miles away. I just used regular CATV coax. I have a friend with SWR meter... will have to run it through to see if it needs any tweaking. Thanks for the Instructable!

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jcoman made it!(author)2014-12-30

Awesome! I'm glad you got something out of this project! You mention CATV, are you in the CATV industry? I ask because I am.

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MrSquare made it!(author)2014-12-31

Nope, I'm just a general techno-jack-of-all-trades. I'm currently in IT but just got my HAM license in May and I like that there are instructions out there on how to make almost anything you need for it, if you're willing to spend the time to learn how.

I let my friend borrow this antenna and she was able to reach back to me on my base radio and handheld. I just need to build a few more now! :)

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MikeWA6ILQ made it!(author)2014-08-10

Safety feature: The locals that have used these for transmitter hunt antennas for the last decade or so discovered something a long time ago... The edges of the tape measure section can be VERY sharp and can cut a gash faster than you can blink. I'd do two things: first, use a file on the sharp ends to reduce the sharpness as much as possible... Second, cover the ends with something - the most common thing you see around here is a piece of cloth duct tape folded over each end of each element.

BTW, if you have a Harbor Freight in your area, walk in and sign up for the snail-mailed coupons Every so often their monthly snail-mail flyer includes a coupon for a free 25 foot (by 1 inch) tape measure just for walking into the store (no purchase required). Two other frequent freebies are a low-end-DVM or a 6-piece screwdriver set (both of which live in my ARES go-bag).

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kc8hps made it!(author)2014-04-20

Ive seen a number of antennas such as this. Im curious where and why the 5" piece of wire is used. Is the wire a matching section or impedance balance component?

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jcoman made it!(author)2014-04-20

You are absolutely correct, it's a hairpin match. It's the simplest match for this type of antenna, with the added bonus that it is light weight and compact as compared to something like a Gamma match.

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kc8hps made it!(author)2014-04-20

Thanks so much for the clarification.

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zawy made it!(author)2014-01-13

I guess the camera "fish-eye" effect is making the top length look longer than the middle length. At least I can count the inch marks and see the top length is off-center by 1 inch, having 18 inches to the left and 16 inches to the right. I assume you've caught that by now and adjusted it.

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jcoman made it!(author)2014-01-13

If I remember correctly, it was actually 2" off. The photo was pre-SWR meter testing. I'm surprised you caught that; Even though it was new, I cut the tape a foot in from the front so I didn't have holes in the element. Thanks!

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zawy made it!(author)2014-01-13

It is important where the 2 cut pieces meet in the middle to be as close as possible. The total length of the two lengths plus the space should probably be 17.5" in order to be ideal according to the software that the original designer was using. I would trim off 1/16" from those pieces to see if it improves. Car anteneas use a spiral groove to add inductance and a metal ball at the top to add capacitance which matches with the characteristics of the surrounding air better. So I bet there's a way to improve upon even yagi designs.

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jcoman made it!(author)2014-01-14

An inch between the ends of the driven elements seemed to work pretty well for me in this design. When I moved the driven elements closer or father from each other, the SWR changed, and not in good ways. At exactly an inch, I had just a touch over 1:1 but under 1.1:1 on the SWR meter at the frequency the elements were cut for. It's the best I was able to achieve and really good considering. Funny you mention car antennas, I actually scavenged several yesterday because I was thinking the next project with my nephew would be a Yagi built out of them.

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profpat made it!(author)2014-01-12

nice instructables!

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spark+master made it!(author)2014-01-12

Copper cacti were used by Hams in apartments with terraces and a no external antenna rule (of any kind). So you plop it in a Ceramic Vase and call it sculpture. (fer real).

Ladder line hard to get (jpole) Take a piece of plastic corrugated "cardboard" shove the appropriate pieces of "12 solid down two of the corrugations at the right distance from each other (parallel)make the connections take silicone sealant and squirt into the open ends of corrugations. There will be 2 or 3 empty channels near the middle pull some fishing line through them to make a nice hanger. while this will not roll up it is also light and you can with aid of rope pull it up into a tree.

Get dimensions for ladder line from the net. Alternatively you could just glue the wire to anything for the spacing add a hole to the "backer board" add the string.

Then you can build the attic antennas! (quaggie)

Ciao

chris

author
spark+master made it!(author)2014-01-12

OH I fergit, let him make a Jpole and a Copper Cactus. The CC will let him/her use flames. Nothing better'n flames and ham radio. Sometimes the radio provide both!

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jcoman made it!(author)2014-01-12

Interesting idea! I think I'll do that. One can never have enough antennas and I'm sure I have some copper laying around somewhere. Thanks for the idea.

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FN64 made it!(author)2014-01-12

Glad to see another "Elmer" in the mix. I made one of these a few years ago from Joes plans. Works quite nicely!

All my best to the young fellow working on his ticket.

Here's a look-see at the one I put together.

https://www.instructables.com/id/Radio-Direction-Fi...

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jcoman made it!(author)2014-01-12

Thanks! These things work really well; of course why wouldn't they? Yagi's are pretty amazing antennas.

I didn't find yours until well after I posted this one. These are fun because they are so simple to put together. Definitely a great project.

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spark+master made it!(author)2014-01-12

2 meters?

how about 6 meters?

nice instructable and Kudo's as well to the guy who thought it up! (WB2HOL)

the new 1 inch wide rulers really can work well and being able to roll them up is a hoot.

Great for a back pack if you use "rollers" to roll them up to stay put and then get to top of say Bear Mountain in NY and fire up the Limark repeater system! I did it with a crappy rubber duck on an HTX 202 on Lo Power, dfq even. This would make it even better!

Height makes mite they say! so put it in a tree.

ciao

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Florizzz made it!(author)2014-01-08

good hunting! 73

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jcoman made it!(author)2014-01-10

Thanks! That's one of the things I plan to try to get him into when he gets his ticket. 73!

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