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| | |-+  Airband Yagi antenna designs
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Author Topic: Airband Yagi antenna designs  (Read 46037 times)
dorough
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« Reply #30 on: July 15, 2009, 03:50:36 PM »

Would it be a good idea to use 1/4" threaded rod for the elements?
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dave
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« Reply #31 on: July 16, 2009, 10:39:44 PM »

Would it be a good idea to use 1/4" threaded rod for the elements?

Should be OK.
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spielberg
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« Reply #32 on: July 17, 2009, 04:23:11 PM »

I've just finished this antenna and it works like magic! I've had an own built discone antenna and I should say that this Yagi works so much better! The only problem I can see is that Yagi is a directional antenna and you need to spin it around to find the best position for every frequency, depending on the direction of the airport and transmitters, while a discone antenna works in all directions. But I can live with that. Thanks for posting this antenna idea, guys.
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FlyGuyAlex
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« Reply #33 on: September 27, 2009, 08:25:28 PM »

I also just made this.. Works fine but is still not what im looking for.
Im trying to pick up a ground station about 40mi. anything that can do that?

Thankss
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dave
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« Reply #34 on: September 27, 2009, 08:29:39 PM »

I also just made this.. Works fine but is still not what im looking for.
Im trying to pick up a ground station about 40mi. anything that can do that?

Thankss

The only thing that will help in this case is elevation.  smiley  But it depends somewhat on the ground elevation at each end of the path.  Are both ends around sea level?
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FlyGuyAlex
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« Reply #35 on: September 28, 2009, 06:32:53 AM »

The ground stations are up high in mountains.. and im at sealevel but on the roof so about 20ft AGL
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dave
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« Reply #36 on: September 28, 2009, 03:35:52 PM »

The ground stations are up high in mountains.. and im at sealevel but on the roof so about 20ft AGL

It also depends on what the remote station's antenna pattern looks like - and how much transmitter power they use.  Another factor is local noise at the receiving end (your end).  In that environment there can frequently be power line noise due to salt water and other corrosion effects.
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FlyGuyAlex
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« Reply #37 on: September 29, 2009, 03:20:46 PM »

Dave,

We have much noise on my antenna inputs because of radio stations. Our powerlines are burried in the ground so i dont think that can be a problem. I'm using a bandpass filter to get out the radio stations. Anything other i can do?
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dave
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« Reply #38 on: September 29, 2009, 03:57:41 PM »

Radio stations: AM or FM?
How far are the offending transmitters?
Multiple all in one location or just one?
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propwash
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« Reply #39 on: November 28, 2009, 05:54:28 AM »

Wow!  Thanks for getting me motivated to build something very similar based on those plans.

Unfortunately, the beam is currently indoors, so I run boom-less just hanging the elements from the rafters and letting gravity keep the wires straight.

I am also using an unconventional driven-element dipole, which consists of a quarter-wave wire attached to the center conductor of the coax feedline, and for the other side of the dipole, I use 4 ferrites (Radio Shack 273-105) snap-ons a quarter wave AND at a half-wave point down from the feedpoint.  This way I'm forcing the common-mode of the braid serve as the other half of the dipole.  The feedline serves as part of the bottom half of the dipole and the feedline itself.

(Normally instead of using a coil of coax for a choke, I like to use 4 of the type-43 ferrites right at the feedpoint, but in this case, I purposely move it down a quarter wave to emulate a wire.  Makes an interesting alternative to a j-pole driven element)

I'm still playing with the reflector spacing since I'm using 75 ohm coax, and hope to switch to 50 ohm soon.  But for now, the results are good, so thanks for publishing those specs!!

This is the first beam I've built, and now you've got me hooked!  Must make one for real outdoor use however... Smiley


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dan9125
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« Reply #40 on: December 16, 2009, 09:47:00 PM »

I have a question about the homemade Airband Yagi antenna antenna that Dave built. The plans call for the reflector element to be 48" long. Is that 48" total or is it 48" on each side of the boom?  The plans are not very clear on that.
  Thanks in advance, Dan
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dave
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« Reply #41 on: December 16, 2009, 11:12:16 PM »

That is total element length.  Divide the driven element length in half to get the length of each of the two element halves.
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dan9125
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« Reply #42 on: December 17, 2009, 08:31:15 AM »

Thanks Dave, thats what i thought but wanted to make sure. Hope to have one attached to the KBUF feed soon.
   Dan
 
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dan9125
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« Reply #43 on: December 28, 2009, 09:21:33 PM »

Finished my airband yagi today, hoping it improves reception. I wont be putting up for a week or two as its 19 degrees F and 30 mph winds in Buffalo. I used an old VHF TV antenna, moved and trimmed a few elements to spec. Had some 50 ohm Belden 9913 laying around so this hasn't cost me anything yet. Here is a pic.
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dave
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« Reply #44 on: December 28, 2009, 09:28:09 PM »

Strong work!  Hope it works well once you get it installed!
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