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Scanner / Receiver Antennas - For discussion of any type of receiving antenna used by a scanner or receiver base, mobile or handheld.

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Old 08-18-2006, 4:46 PM
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Default Yagi antennas for under $5

I had a need for a UHF Yagi antenna last night and the only place open to get parts was Wal-Mart For less than $5 I was able to build a very decent 6 element yagi for 450MHz that works well for both transmit on the 70cm amateur band and receives well for most 440-470MHz use. below are pics and materials.

Materials:
10 pack of wire clothes hangers - $0.97
Wooden dowel, 3 feet by 5/8 inch - $1.56
Can of spray paint - $0.99
This list may go up if you need to buy tools or glue.

Additional Materials:
Glue, epoxy, chewing gum or something to hold the elements solid to the boom. I used hi-temp hot glue

Tools:
Drill and bits appropriate for the diameter of wire used
Heavy wire cutters, linemans pliers work best

Howto:

Measurements (In Inches):

Reflector: 13.0
Driven Element: 12.5 inches (SEE NOTES!!!)
Director 1: 12.1 inches or about 12 1/8
Director 2: 11.75 In
Director 3: 11.75 In
Director 4: 10.75 In

Spacingmeasured from Reflector)

Driven Element: 2.5in
Director 1: 5.5in
Director 2: 11.0in
Director 3: 18.0in
Director 4: 28.5in

This part requires a steady hand or if you have it a drill press. Clamp the dowel to your work surface and drill as strait as you can the holes for the elements except the driven element. be sure to leave enough room at the back of the antenna to mount it to a pole but so much room that you run out of room before you get to the front of the antenna. 6 inches should be plenty since its 28 inches from reflector to the front director. be sure to drill these holes strait or your antenna will look like crap. Once you have the holes drilled clean up any splinters and roughness you may find. Cut your elements tot he lengths listed above excluding the driven element. The driven element is special and different from the rest of the elements. it is made in two sections. The driven element is a typical half wave dipole so you will need 2 sections. Drill 2 holes for the driven element about 1/8-1/4 inch apart. if your hangers have a rubber coating strip back the coating from the boom ends of the element so you can connect wire to the element. if you have it available use #10 baer copper for the driven element so you can solder to it, but if not you can get by with the steel wire. Cut 2 lengths of wire 7 inches in length and insert into the boom leaving 6 inches of the element exposed on each side of the boom to get the overall 12.5 inch length. You may have to fine tune the elements to get the correct overall length.

You can start inserting your elements into the boom and using your choice of suitable adhesive to secure the elements. Be sure to center the elements so they are even or your antenna will look like crap. Let your adhesive set up before doing any more work to the antenna. once the glue is dry you can attach your coax to the antenna. Attach the shield to one half of the driven element and the center to the other half and using your glue seal the connections and the open end of the coax. if you have it available you can use a 300ohm-75ohm TV antenna balun to connect to the element. you cant solder to steel or aluminum so you will have to seal these connections using epoxy or something similar. Once the glue has cured and you have given the antenna a test run you can paint it. use several coats of a non-conductive paint. i used generic automotive primer. let the paint cure for several hours or all day or whatever works best for the paint you have and find a suitable mounting system and enjoy. The pic is of the UHF yagi and a trial run for a 800MHz yagi.
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Old 08-18-2006, 6:36 PM
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[ The pic is of the UHF yagi and a trial run for a 800MHz yagi.[/QUOTE]


Please advise how the 800 mhz yagi works out for you. Looking to make somethinf similar.

Thanks

B.K.
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Old 08-18-2006, 7:03 PM
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Yes, please let us know how this worked out. I've been wanting to get a UHF yagi for public safety and business and this may be just the solution. How much better were your results than using a 1/4 or 5/8 wave antenna, for example?

Last edited by Gilligan; 08-18-2006 at 7:06 PM..
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Old 08-18-2006, 7:06 PM
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Good, I'll pay you $15 plus shipping.
Let me know where to send the money order!
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Old 08-18-2006, 8:01 PM
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that's what I really call sweeeeeeeeeeeeet!
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Old 08-18-2006, 9:08 PM
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If you want me to build them and pay me for parts and labor I can. The 800MHz antenna works great, I used my cordless phone to test it and it performed great. The UHF antenna can hit a 70cm amateur repeater 16 air miles away with good reports at 1/2 watts in mountainous terrain. If you are serious about $15+shipping then by all means lets do it
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Old 08-18-2006, 10:11 PM
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How big are they overall and how heavy, for UPS estimates?

I'd pay you to make one. I think I could handle it myself but I have other unfinished projects that need to be done first.
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Old 08-18-2006, 10:55 PM
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Hey, everyone slow down. I'm first up!!
I would certainly buy one. What kind of coax connection did you make on this one?
PM me when you have a suitable price.
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Old 08-19-2006, 12:34 AM
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Its light, very light, a few pounds. its 36 inches long by 13 inches tall and less than 1 inch thick. I am still working out some bugs in the 800Mhz antenna, mainly how to connect coax to the element with as little loss as i can get. The UHF antenna coax is just open ended connected to the element.
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Old 08-19-2006, 3:00 AM
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Nice looking antennas, I have experimented a little with a homemade 800mhz yagi, I used standard household copper romex for the elements. It works 'ok'. Nothing to compare it to besides rubber ducky antennas..

Once you get the details worked out on the 800mhz version, I would like the measurements for it, if you have them available, I would like to make another one using the same materials you did.
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Old 08-19-2006, 9:35 AM
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I may also see if I can build a VHF antenna for 152MHz for under $5 and post the results here too. I have one for WX band that is made from PVC pipe and sluminum rod from Lowes, but its overall cost was nearly $20 and its only estimated to be 7db. If I can find metal rod cheap enough I think I can do a $10 Yagi for VHF
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Old 08-20-2006, 12:54 AM
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Quote:
Originally Posted by kf4lne
If I can find metal rod cheap enough
Try a welding shop - brazing rod should be solderable.
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Old 08-20-2006, 8:36 AM
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Or the walmart speciality store, Tractor Supply, if you have one. They are also open on sunday.
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Old 08-20-2006, 1:11 PM
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how and to which element is the antenna wire connected?
guess i'm spoiled with some type of connector always being there. That plus i've never tried this before and think it would be good for me to try
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Old 08-20-2006, 1:37 PM
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Yes, I have that question also. I am ready to build one today. Plus, can someone explain more in detail what to do with the 7 inches of wire that we cut. What kind of wire, and where does it connect to/ and go?
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Old 08-20-2006, 2:37 PM
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Here are the plans for the antenna in a nice PDF document I created. I have made tests of the 800MHz antenna today and it seems to perform exceptionally well for what it is. It rained all morning, but the UHF yagi held up well. It still works great as a TX antenna for 70cm amateur use and there are no noticable problems.
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File Type: pdf 5 Dollar Antennas.pdf (94.9 KB, 6322 views)
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Old 08-20-2006, 2:58 PM
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The coax is connected to the driven element, there is no connector so you will have to wrap the center conductor around one side of the element and the shield around the other. Your driven element should be a 2 peice element since each side of the element needs to be electrically isolated from the other to create a half wave dipole. If you look in the original picture you will see the driven element halves are offset from each other just a little on the boom, thats because the elements are mounted in 2 different holes in the boom about 1/8 inch apart. You connect the coax to each half of this element right at the point where it enters the boom. If you used steel wire for the driven element you cant solder to it, but if you used copper you can solder to it. You cant solder to the shield in most CATV/Dish RG6 because it is aluminum. See the PDF for more detailed information
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Old 08-20-2006, 3:28 PM
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Quote:
Originally Posted by KC2GVX
Yes, I have that question also. I am ready to build one today. Plus, can someone explain more in detail what to do with the 7 inches of wire that we cut. What kind of wire, and where does it connect to/ and go?
The 7 inch wires are the 2 halves of your driven element. Your driven element is a half wave dipole, one side is connected to the center conductor and the other side is connected to teh shield. You drill 2 holes through the boom at the point where the driven element is mounted so you can mount both halves and keep them electrically isolated from each other. They are cut 7 inches because the extra inch is used to mount the element into the boom, and then you have to trim the excess from each end to get the overall length
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Old 08-20-2006, 3:51 PM
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Looks like a great idea Dan.I might try and make one of those.Thanks
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Old 08-20-2006, 5:24 PM
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aso none of the poles except the driver have any wire connected to them and the drive is cut in half seperated by about an 1/8th of an inch with shield on 1/2 and conductor on the other 1/2 correct?
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