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Author Topic: .64 wavelength dipole antenna  (Read 4308 times)
Guest

« on: February 19, 2007, 06:08:20 PM »

I have heard that a .64 wavelength is the highest gain single element design there is for a dipole antenna. Is there any formula for figuring out it's exact measurements and feedline for a 10 meter antenna?  Bill
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K0RFD
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« Reply #1 on: February 19, 2007, 06:21:18 PM »

Call it what you want, but at .64 wavelength, I don't think it's what most of us think of when we think "dipole."
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N8YB
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« Reply #2 on: February 19, 2007, 06:44:49 PM »

Maybe you're thinking if the Extended Double Zepp?  Each leg is .64 wavelength (5/8 wave).  Feed it with 300 or 450 ohm balanced line and a tuner.

Here is some additional info:
http://www.g3zps.com/Page4.htm

73,
 Jerry N8YB
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K3AN
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« Reply #3 on: February 19, 2007, 06:47:10 PM »

Why do you need it? After reading your recent review of QSOnet CQ100, I can't imagine why you'd need to worry about building a real dipole.

"This is the only thing you will need for Ham Radio. I find that this product is so good that many hams are selling all there equipment and just using this. Now that is saying something. You will have to try it to believe this."
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KB1LKR
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« Reply #4 on: February 19, 2007, 06:49:04 PM »

0.64 lamda = "5/8 wave" end fed (over a ground plane)?

I suppose you *could* (doesn't necessicarily mean you'd want to though) center feed a 2 * 0.64 lamda horizontal dipole too (and for 10m it wouldn't have too be extremely high off the ground). Perhaps (awkward, but...) even a center fed 2 * 0.64 vertical  -- am I (theoretically if not practically) right???

Note though for a 50 ohm feedpoint you'll need a matching network.
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KB1LKR
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« Reply #5 on: February 19, 2007, 06:51:52 PM »

Thanks N8YB -- an EDZ & matching section.
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N3OX
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« Reply #6 on: February 19, 2007, 06:59:56 PM »

"I suppose you *could* (doesn't necessicarily mean you'd want to though) center feed a 2 * 0.64 lamda horizontal dipole too"

This is an Extended Double Zepp like N8YB mentioned, and it has significant gain over a halfwave dipole but of course, you have a sharper pattern.  It is about the longest element you can have without the pattern breaking up into more than two main lobes.

A matching network wouldn't be so hard.  I like to use a program called L_TUNER by the late G4FGQ:

http://www.btinternet.com/~g4fgq.regp/page3.html

The impedance of a center fed #14AWG antenna of two 0.64wl elements a half wavelength above ground on 28MHz is about 130-j680 according to EZNEC.

Plug that into L_TUNER and it will spit out inductance and capacitance values for an L-network to match the antenna.  

73,
Dan
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
Guest

« Reply #7 on: February 19, 2007, 07:08:59 PM »

N3OX, thanks Dan, that may be the info. I was looking for I shall check it out. Sounds interesting, I appreciate it. Bill
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W8JI
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« Reply #8 on: February 19, 2007, 07:20:54 PM »

Dan, Did Reg pass away?
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N3OX
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« Reply #9 on: February 19, 2007, 07:28:06 PM »

Tom, regrettably, yes.

One of his children came and posted in r.r.a.a. with the news in August.

Dan
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
KZ1X
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Posts: 3229




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« Reply #10 on: February 19, 2007, 07:38:42 PM »

http://www.sadona.com/news2/ant_dblzepp.html

I built one for 20 meters, for Field Day use, and BOY does this thing kick butt!
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W7ETA
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« Reply #11 on: February 19, 2007, 09:59:26 PM »

Did you check out W4RNL's site?
Bob
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WA6BFH
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« Reply #12 on: February 19, 2007, 11:04:00 PM »

A half-wave radiator, minus about 10% will "capacitively lead" in current distribution. You might want to try this?

Use a good counterpoise system.
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Guest

« Reply #13 on: February 19, 2007, 11:20:51 PM »

Thanks all for the help. The antenna I was wondering about is on this link: http://www.gd7jwr.com/page3.html     73,s Bill
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WA1RNE
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« Reply #14 on: February 20, 2007, 08:13:43 PM »


 The EDZ on GD7JWR's web page is really the best way to design an EDZ for a single band.


 To my knowledge, it was K7KGP who made this particular design popular and authored an article describing it in the December 1987 edition of QST. His design was for 12 meters, but the theory and formulas were provided to design one for other bands.

 The key to the design is the 450 ohm line that's used as a transmission line transformer, which is 52 electrical degrees or 0.145 wavelength long. N3OX's EDZ feedpoint Z calculations are very close to K7KGP's, who indicated they were in the order of 142-j555 ohms and at the time confirmed by the ARRL on a Smith chart and MININEC via an "IBM PC". (we've come a long way with EZNEC and PC's!)

 The article also described a phased array of 2 EDZ's spaced at 1/8 wavelength for close to 5dB of gain.

 I built a single EDZ for 15 using this design several years ago and it worked very well.


 .....WA1RNE
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