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Homebrew 1.2 Ghz 10 element yagi antenna

Discussion in 'Home Brew' started by Moleculo, Aug 30, 2009.

  1. Moleculo

    Moleculo Administrator
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    I've been wanting a 1.2Ghz yagi so I could try to work the AO-51 satellite on 1.2 with my Alinco DJ-G7. After looking around at commercially available antennas, I decided to build one myself with some of the plans that are available online.

    The design and specs are from WA5VJB. He says the measured gain is 13.5dbi. I followed his plans for the 1.2Ghz antenna almost precisely. The antenna elements are 1/8" steel rod and were measured using digital calipers. I wanted to use bronze or some other material that wouldn't rust, but Home Depot was out of the bronze rod on the day I happened to go there. The boom is a a 3/4" square wood piece, a little less than 4' long. I cut off a little of the excess. The elements are within a few 10,000's of an inch of the specs! I also carefully centered them on the boom from side to side and top to bottom so that they're all properly aligned

    Here is the finished antenna:

    [​IMG]

    The driven element is 12ga house copper ground wire. (WA5VJB used 10ga wire, but it shouldn't make any difference). I had some excess on the shelf in the garage, so I put it to use. I also had some RG8x that already had one PL-259 on it, so I just used that for the connection to the driven element. You can also see that all of the elements are epoxied into place.

    [​IMG]

    You could move the driven element up on the boom and drill two holes, but it just happened to work out that the center of the square wood allowed for the driven element to be exactly 1/2" in diameter with the bottom of the element epoxied to the boom. I plan on covering the coax connection with RTV silicone, but I wanted to leave it bare for the picture.

    [​IMG]

    And finally, here is the intended use for the 1.2Ghz yagi. The square wooden boom lays nicely on top of the 440Mhz Arrow boom and I just velcro'd them together. This is starting to get a bit heavy for handheld use, but I'll give it a try and see what happens.

    [​IMG]

    I don't have an SWR meter for 1.2 Ghz yet, so I don't know what the bandwidth of the antenna is. A quick test however confirmed that the antenna indeed has some good gain! I was able to hit a repeater with my 1 watt HT that is about 37 miles away that I could never hear or hit before (y).



    I've attached the design specs, which also includes plans for 2m, 220, 440, and 900 Mhz. If you plan on mounting this outside, you could easily attach a u-bolt. You would also want to weatherproof the boom and elements using some paint, marine varnish, or similar. Total cost for the antenna (not including coax & PL-259) was exactly $10. (y) Half of that cost was for the epoxy.
     

    Attached Files:


  2. Luke_C

    Luke_C KD0GBK

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    Allright, let me get this striaght. :p

    You stick the rods through the wood at proper dimensions and secure them in place. Attach the driven element, and solder that up.

    The stick it on your HT and wave it around? :D

    I'm a total bafoon with antenna's, and i think I may manage this. I want to build one for use with my 2m HT and see how far I can reach. This seems pretty darn impressive.

    Do ya think 5.5w on 2m would get 30 miles into a repeater? This would be especially nice for camping where bigger radios stay home, but it's nice to still get good range.
     
  3. Moleculo

    Moleculo Administrator
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    LOL, yeah something like that. It's more like "aiming" than "waving", though.

    Well that depends on what is in the way. If you're on pretty flat ground, I would think you could get into a repeater with a 5 watt HT with the stock antenna. However, If you make one of these antennas for 2m, I guarantee you that you'll be able to get a lot farther range than that with 5 watts!
     
  4. Luke_C

    Luke_C KD0GBK

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    Mol,

    Sorry, I wasn't clear. I meant 5w on 2m from a HT. Do ya think that'll get 30 miles of range? I'm in the mountains at 7k ft, but I'd be shooting 'downhill.' Not a whole lot in the way to the repeater. I hit it regularly with my base.

    Correct me if I'm wrong, but the elements aren't connected to each other?

    I need some 'antenna building for beginners.'

    I'm going to try this one on my days off next week. Looks pretty doable.
     
  5. Moleculo

    Moleculo Administrator
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    If you have that much elevation on the other station, your 5 watt HT should get 30 miles with the stock antenna. The only thing that could be a factor is if you're in a canyon or behind a ridge.

    No they're not. The one in the back of the antenna is a little longer than the driven element and is called the reflector. By having properly spaced and progressively shorter director elements in front of the driven element you achieve gain and directivity. The more elements, the more gain. You can also build it using a metal boom, but then you have to compensate by altering the length of the elements..

    To make one of these antennas, you really only need a few tools. You need something to cut the 1/8" rod, something to drill the holes, and something to measure with. I used a dremel tool for the cutting, my drill press (you could easily use a hand drill, just make sure you drill straight) and a cheap pair of digital calipers. Everything else you need except the soldering gun is just basic hand tools.
     
  6. C2

    C2 Sr. Member

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    You ought to try a bi-quad or double bi-quad antenna.

    I built a bi-quad for 23cm and measured a bit over 9 dBd...

    A lot easier to handle than a long beam.
     
  7. kc0zhf

    kc0zhf Member

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    it can be done, when i went to cheyenne (many moons ago) i use to get the repeater with 5 watts to skyline mt. (Denver) repeater 80 miles away as the crow flies, very senceitive repeater i might add, with a 2 meter version of this. (the secret was the smog??)

    i will try this version with a IC-x2a HT this week on AO-51 and see how it does, thanks for the pictures,
     
  8. Moleculo

    Moleculo Administrator
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    If you don't already have a 440 yagi (like I did), you might build it this way (only for 1.2/440) like she did:

    [​IMG]
     
  9. C2

    C2 Sr. Member

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    double yummies on the bipod...and those are NOT 3M earplugs.
     
  10. RickC.

    RickC. Hopeless antenna junkie

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    Nice work!
     
  11. kd0fx

    kd0fx W9WDX Amateur Radio Club Member

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    If my local club had members like this, I would join.
    Do the orange caps on the elements do anything, or are they just there for eye protection?
     
  12. Moleculo

    Moleculo Administrator
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    They're foam earplugs stuck on there for eye protection only.
     
  13. linearone

    linearone King of NY

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    this is real radio at its best.

    very cool.

    I love cheap homebrew projects like this.
     
  14. linearone

    linearone King of NY

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    man, everything is better in cali, the surf, the antennas, the ham operators (they dont look like that here)
     
  15. C2

    C2 Sr. Member

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    Well, I'm not sold yet. She seems like a front...is that not a black nightie???

    [​IMG]

    But the designer did make a comment on her blog...

    Make: Online : Catching satellites on ham radio
     

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