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I needed an antenna to chase down a noise source.. After much ado I settled on some plans I found on the web, added my own modifications & took some photos along the way. It has a cardoidal pattern with a deep null on the rear. I made a few minor changes to the original design but these were mostly for structural integrity, looks & ease of assembly.
This antenna will DF noise or signals in the area of the 2 meter amateur radio band..(144 - 148 MHz). I have tried it as high as 155MHz with good results. It is flexible so it won't break or bend as will most commercial directional antennas. It also tunes well on the 2 meter band.

You will need the following:
# A tape measure with a 1 inch wide steel tape. (Or a replacement tape)
# 3 PVC crosses for 1/2 inch pipe.
# ~3 ft section of 1/2 inch PVC pipe.
# 2 stainless hose clamps for 1 1/4 dia hose.
# Electrical tape.
# Soldering iron & associated tools.
# 6 feet or more of 50 Ohm coax & connector (BNC, PL-259, SMA...)
# Scissors or small shears to cut steel tape.
# Hack saw or tubing cutter to cut pipe.
# A Dremel tool is handy but sandpaper will do.
# You will need a receiver that has an "S-meter" to locate the direction of the signal.

Step 1: Cutting the Tape Measure

Remove the tape from the tape measure and use the tail end for your elements.. This part sees much less wear & tear than the first 10 ft or so.
Measure your elements to the following dimensions.

# Reflector: 41 3/8 inches
# Driven element: 35 1/2 total.. cut in half for 2 @ 17 3/4 inches
# Director: 35 1/8 inches


These can be cut with regular scissors.. BE CAREFUL.. The ends will be quite sharp. I cut all ends with 45 degree angles. Some folks have taped or dipped the ends in Plasti-Dip but I just sanded mine a bit to take the sharp corners off.

Step 2: Assembling the Reflector & Director..

Mark the center of these elements with a sharpie & slide them through a cross till they're centered. You might need to sand the "stop lip" inside the cross a bit to make this easier.

Cut 4 pieces of PVC pipe about a half inch long. These "keepers" will hold the tape centered in the reflector & director crosses. Sand off any burrs.

I used a "C-clamp" to squeeze the little "keepers" into the crosses but a vice would probably work as well or better.. They can also be tapped in with a hammer if you're careful & use a block of wood or dowel as a driving pin. Make sure your tape stays centered.

Step 3: The Driven Element

The feedline is connected to the driven elements directly through a "hairpin match" This was the original concept and it works well so I followed suit.
Cut a piece of solid wire (14 gauge or smaller) 5 inches long. Form this into a shape resembling a tall "ohms symbol". Strip 1 1/2 inches of cover off the coax & separate the core. Solder the coax to the hairpin as shown in picture.. Trim the excess coax wire close to the solder. The ends of the hairpin need contact with the elements but soldering is extremely difficult on the steel tape. I crimped & soldered some small connector lugs to the ends of the hairpin and these are contacting the steel under the hose clamps. The tape measure sections need to be sanded to remove any coating at the contact area.

Step 4: Setting the Element Spacing

Cut a piece of pipe 11 inches and another at 7 inches. Sand any burrs from the ends. These will set the spacing nicely.. I didn't "glue" anything.. they're held together by a tight fit.
The 7 inch section goes between the reflector and driven elements.
The 11 inch section goes between the driven elements and the director.

Step 5: Tweaking, Tuning & Using

Not only will this antenna function well as an RDF unit, it will also tune well for transmit on 2 meters.

The SWR is adjusted by tweaking the distance between the driven elements. Mine is set at 1 inch for a 1.3:1 match.

The radio I use is an old Realistic HTX-202.. I was getting some RF on the feedline causing the rig show an error message. I wound 7 turns of the coax around the pipe that connects to the reflector & secured it with wire ties and electrical tape.. That cleared the problem.. Depending on your use, you may or may not need this step.

Using the antenna for RDF is easy.. USE the BACKSIDE to find the NULL. (second photo). The front lobe has quite a wide beam width but the null on the cardoidal pattern tells you much better especially when you get closer to the source. Watch your S-Meter as you swing the beam from side to side. The weakest signal strength indicates the direction.

If you bought a 10 foot section of pipe, the remainder can be used as a mast of sorts. Just insert the end of it into the cross that holds the driven elements. With 6-8 feet of coax this allows plenty to reach the rig.

This antenna folds up nicely to fit behind a car seat or for storage.. (third photo)

Step 6: Final Thoughts.

This wouldn't be complete without credit where it's due.
Joe Leggio - WB2HOL started this whole concept and I encourage you to check out his methods and explanations as well as his other RDF projects.
Joe's Design

So there you have it. I don't have a cost rundown but 10 bux is a reasonable guess.. Some of the parts were junkbox items. Hope you enjoyed my first go at Instructables
73..FN
<p>Great project! Can you supply the measurements in METRIC?</p>
<p>Question: Why use a tape measure instead of some metal rod? Do they behave differently?</p>
Yes.. In fox hunting there are many occasions where you will be going through trees, brush &amp; heavy undergrowth where a rigid antenna element would either be a hindrance or it would break.<br>The flexibility of the tape will just wrap around you as you go and spring back into shape after you're through a thicket.<br>Hope this explains it &amp; thanks for the question.<br>..FN..
<p>Tuned easily to 1.2:1 on 145.800 for ISS, no contact for me though :(</p><p>Ill try agiain soon</p>
<p>Thanks for the detail information. In one of the engineering college in India we have taken up this project in Antenna workshop. All student were able to made 16 Tape antennas. </p>
<p>I have made these before in the past, using a tape measure and a wooden yard stick. The work well for Fox hunts, too.</p>
<p>nice concept for light weight antenna for transport thanks de VU2PLL </p>
@shhammer... Sorry I didn't clarify that in the 'ible. <br>It will work well for ya but it takes a bit of tinkering to get it together. <br>Thanx for the comment.
Appreciate yours and Joe Leggio's work. I've built it but not tested it yet. One point of note. Where talking about &quot;you might need to sand down the stop lip inside the cross&quot;, I think you might want to change that to &quot;you WILL need to ...&quot; I spent the better part of an hour trying to force the keepers in without sanding down the lip. Didn't work. Ended up both sanding down the lip and then tapering the keepers some to be able to get them started. Thank goodness for Dremel tools. :) Keep up the great work. <br>73 ... KD0WSW
Question -- If you use EZNEC's Antenna Program to design the spacing for the Yagi Antenna, What would you use for the diameter of the wire. <br> <br>Basically, I want to design the Measuring Tape Yagi Antenna to be sensitive in the MURS Frequency Range. I want a good Front to Back dB ratio and overall gain for the Antenna. My class has a Rabbit Hunt (*A Fox Hunt but in Clean Room Rabbit Outfits*) and the teacher uses the MURS frequency 151MHz to 154.4MHz. Well, Thanks for any reply.
@KF7UWU.. <br>I've had great luck with 5-10 watts.. Above that it's hit or miss if I get an error message on my rig. I went to 25 with a Yaesu 1500 &amp; was OK but when I upped it to 50 the rig got all weird on me.. I was within about 10 ft of the antenna at the time so I'd say it was either &quot;near field&quot; RF or common mode currents on the feedline that the small choke coil of coax couldn't stop. <br>Thanx for checking my 'ible out &amp; 73..
Great Instructable! How much power can this handle? <br> <br>KF7UWU
A realy natty bit of junk box tech. I found all the bits under the bench and dug out an old tape i chucked in the scrap bin a couple of days ago. <br>I squirted 5W of RF into it and opened the local repeater too. <br>good instructable, best 73's from G7WJJ
Great! I've been looking for a design for a tape measure Yagi on the Net for a while now, and you have provided the perfect article. I'm going to use mine for QRP (5W) bicycle mobile.<br><br>Thanks for the great 'ible!<br><br>(I didn't intentionally copy your account pic btw)<br><br>73<br><br>WE
No prob on the avatar... it belongs to the ARRL but is available for hams to use.. Glad you got some ideas.. feel free to make your own improvements as you see fit but do kindly give credit to Joe Leggio who came up with the original concept..<br>Best 73.. &amp; I'm good on qrz<br>_. .---- -- .-.. ..-.
Iv built one of these before when I 1st got started. I'm thinking heavily about adding it to my EmComm box that was created after April 27. Thanks for posting and 73s on future Ibles<br><br>Adam<br>KJ4ZVQ
What are the formulas for the element lengths and the boom distances? &nbsp;I would like to build one for DFing&nbsp; ELTs on 121.5 mhz.&nbsp; Thanks.
Whereas I started with someone else's design and made my own few improvements on it I have no idea what the original formula might be.<br>If there's a ham in your are with an antenna analyzer then some experimentation will set you on course.. The short answer is... as the frequency decreases, the element length increases. Make one with ALL elements a couple inches longer then trim to the resonant frequency.<br>73 &amp; good luck.<br>Fn
Although I'm not a ham (yet) I like this design, and because it is in the 2-Meter band will it work well for FM? I want to make a portable, strong and cheap FM antenna, and this is just the type I'd need. I use 300-ohm cable for FM and to use this I'd say I would have to remove the 'ohm symbol loop'. So, will it work well for FM?
It was designed by Joe Leggio for the 2 meter band.. (see link to Joe's page in my article).. Frequency is frequency so the mode should make no matter.. AM, SSB, FM or CW The resonant freq will be the same. <br>For 2 meter work I'd recommend staying with the 50 ohm coax. Most 2 meter gear is made to a 50 ohm standard. <br>Strength and rigidity are NOT the strong points... Flexibility &amp; ease of use apply far better.
Great idea.&nbsp; Do you have trouble with the tape rolling or collapsing in the wind?&nbsp; KC9PYD
I gotta say Yes and No.. If the convex side faces the wind then yes however the concave side is more wind resistant. Nevertheless, not hurricane proof. LOL<br>That &quot;flexibility&quot; was one of the things I liked about the idea. If you're fox hunting and need to run thru the brush then hold it in front of you with the convex side forward &amp; it folds around you. Try that with an Arrow Antenna!!!. Similar specs with a 50 dollar price tag!!! One day of fox hunting &amp; you have some scrap aluminum.<br>73..&amp; sorry bout delay in response..<br>FN
this will work for a 2meter 2watt ht right? cool idea and i think i'll build it.<br /> 73's, KC2VDM
It will work fine for tx as well as rx. I wouldn't recommend anything over 10 watts unless you get enough feed line to be away from the near field rf. I don't know how much power it will handle before a meltdown so you're on your own on that one. <br /> Good Luck &amp; 73 <br /> N1MLF ..fn64.. Jon<br />
can it be used as a transmitter and well, for 5 watts (what my hand held can put out) it sure would be useful when im just out side of a repeater....
Sorry for the late reply OM.. been out of the country.. YES.. it works well. thats the reason for the hairpin match and the choke coil to keep rf off the braid.. I've run 25 watts without problems but when I tried 50 it caused errors in the rig due to near field RF. Should be a great boost for a 5 watt HT.. Thanks for the comment N1MLF...Jon
ok, do you think that it would work on 50watts?
KI4PSR, Dave, with the Williamson County ARES group made up a pile of these kits and we assembled and used them for our EmComm Fox Hunts. They work great as a transmitting antenna. I am preparing to build one as a test bench to see just how many watts it will dissipate before melting down. All Hail KI4PSR! 73's Dave N4CVX
ha i used a tape measure to make a di-pole bac in the pirate radio days. cracking idea
great instructable, stumbled across it before i was a ham, and was recently looking for a collapsible Yagi, remembered this, and i'll be building myself, and probably another buddy one for emcomm purposes. 73 from KC9OCD
In the Image for step 1, shouldn't the reflector be the long element and the director the short one? I believe you have the tag's reversed..
Looks like he must have fixed those tags by now.
I made one of these about a year and a half ago. They do work pretty well for camping or any other temporary set-up. At the end of the boom (reflector side) I added about a 6 inch piece of PVC that then joins into a 90 degree bend. I then added a 1 foot piece of PVC that connects into the 90 degree bend on one side and is not connected to anything on the other. This makes a great handle for the antenna and works very well for securing the coax for storage. Also when using it for RDF keep in mind that cross-polarization drops the signal about 15-20 db. USE THIS TO YOUR ADVANTAGE. KC9FSH
I made one of those 10 years ago and still use it to this day! I made it as a backpacking directionnal antenna and between that and my roll-up j-pole I had all I needed for my 2m portable.
oh wow! just what ive wanted to make for a while now! thankyou for posting! a "+" and faved!
Excellent instructable, well done pix. Thanks for putting it on this site. BTW I need FN64 on 2 and 6 meters. I'm in EM20
Hey HamO.. Tnx for good rating. I've been lurking here for awhile & figured it was time I gave it a try. We might get a lift on 6 sometime but a peek at the map sez 2 would require the birds. No AZ/EL right now.. that's another project ..but have 3 ele on 6 up @ 30-35.

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