802.11a Antennas? Did search

802.11a Antennas? Did search

Postby hugenbdd » Thu Aug 29, 2002 3:55 pm

I recently aquired some 802.11a equipment. I am very happy with the performance, however I'm not happy with the distance. I am looking for some 802.11a antenna's. I did a search on the forums and didn't find very much.

Does anyone make antenna's to buy?
Is there a "pringles" can version for 802.11a?

I did find this site on a quick yahoo search but that's about it.
http://www5.cs.cornell.edu/%7Eeckstrom/802.11a/primestar/
but all they seemed to do was put a soup can around the current antenna on the AP with the primestar dish, and wrap the ap in tin foil. All I'l looking for is a way that I can connect while I'm outside of the house maybe 25 feet away without losing the signal.

Thanks for any help
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frequency matters

Postby Pow » Fri Aug 30, 2002 5:50 am

antennas are designed for frequency not protocol.
what you want is probably an antenna for 5.150 - 5.850GHz band.

Pringles version for this range would be same design but scaled about 2x smaller.

You can use any existing microwave antenna design, just scale all details to your frequency.

I'd say go for the waveguide fed dish.


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Antenna designs

Postby nashr » Fri Aug 30, 2002 6:12 am

Lincomatic gave me this link at his site:

http://www.geocities.com/lincomatic/homebrewant.html

It's the best, easiest batch of antenna designs I've come across yet. There's a "toothpick", omni, a cantenna, patch, etc. He's got it all, and they're the best I've seen. As soon as I get a couple pigtails I'm building a toothpick for stumbling, and an omni for driving.
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Postby Thunderforge » Fri Aug 30, 2002 8:34 am

Greg Reh'm Site has a calculator for wave guide antennas, but I don't know if the background formulas are specific to a 2.4 GHz range.

Putting in a diameter of 1.5" gives you a TE11 of 4611.51 and a TM01 of 6023.23 so it would cover the full range used by 802.11a, unfortunately it doesn't show any of the probe placement or can length information because it falls outside the 2.4 GHz 802.11b ranges.

As I said, I'm not positive the background formulas aren't 2.4 GHz specific, but I don't think they are. I believe they are all standard microwave formulas.

At least it's a starting place.

Linc's software errors out on the probe positioning and can lengths too.
Back to the forge,
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Re: Antenna designs

Postby hugenbdd » Fri Aug 30, 2002 12:09 pm

Originally posted by nashr
Lincomatic gave me this link at his site:

http://www.geocities.com/lincomatic/homebrewant.html

It's the best, easiest batch of antenna designs I've come across yet. There's a "toothpick", omni, a cantenna, patch, etc. He's got it all, and they're the best I've seen. As soon as I get a couple pigtails I'm building a toothpick for stumbling, and an omni for driving.


Thanks for all the links. Still some more questions.

Since it will be very hard to find a can that is 1.5 to 1.6 inches in diam. would a piece of coper pipping that is 1.5 or so work? or would PVC work better if I can find it.
Again, length of the "can" matters also correct? so if a pringles can is 12 or so inches long then I would want a piece of PVC that is 6 inches long and probaly place the probe( which is a length of 1.21 / 2 = .605 inche/s long) from the back of the can by about 1 inch.

I guess I will be experimenting the weekend.. Let me know if any of these measurements sound off to you guys.

Thanks for all the help!!
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Re: Re: Antenna designs

Postby rogerRabbit » Fri Aug 30, 2002 12:47 pm

Originally posted by hugenbdd
Since it will be very hard to find a can that is 1.5 to 1.6 inches in diam. would a piece of coper pipping that is 1.5 or so work? or would PVC work better if I can find it.
Again, length of the "can" matters also correct? so if a pringles can is 12 or so inches long then I would want a piece of PVC that is 6 inches long and probaly place the probe( which is a length of 1.21 / 2 = .605 inche/s long) from the back of the can by about 1 inch.

Without running through the calculations, I would guess you should start trying at around a diameter of 1.5" and a length of 9". Remember than a Pringles can is way too short to be an efficient 802.11b waveguide. And you can't be serious about using PVC???
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Antenna designs

Postby aa1a » Sat Aug 31, 2002 7:34 am

IMO antennas are the most interesting aspect of stumbling. Started hamming in the early 50s and probably have used em all by now. For 2.4gc. the spiral helix is great and even a short one is good for illuminating a dish from 1 to 10+ feet as it gets real louder.
Has anyone applied to FCC for certification of their antennas?

The pringles feed or 'polarplexer' as it was known in the 60s is a great portable, directional, easily rotated for V-pol vs. H-pol. and gets real killer if your were to couple into a folded aluminized cardboard box of the right 'horn' dimensions for DX, say out of your van on a high hill...

I am a refugee from 10ghz. ham radio where 300 miles on a 1' dish can be done, unlimited BW, but hams are a dying breed and mostly use cell phones now besides you guys are having more fun.

73s de Dave - AA1A - FN42pb - where wireless really took off in 1906 with the world's first radio voice broadcast and many inventions including antennas...
http://www.radiocom.net/Fessenden
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Re: Re: Antenna designs

Postby stonent » Sat Aug 31, 2002 8:45 am

Originally posted by hugenbdd


Thanks for all the links. Still some more questions.

Since it will be very hard to find a can that is 1.5 to 1.6 inches in diam. would a piece of coper pipping that is 1.5 or so work? or would PVC work better if I can find it.
Again, length of the "can" matters also correct? so if a pringles can is 12 or so inches long then I would want a piece of PVC that is 6 inches long and probaly place the probe( which is a length of 1.21 / 2 = .605 inche/s long) from the back of the can by about 1 inch.

I guess I will be experimenting the weekend.. Let me know if any of these measurements sound off to you guys.

Thanks for all the help!!


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Postby ted » Sat Aug 31, 2002 8:59 am

A brief comment: The waveguide antena calculations are scalable, so you may be right (I have not verified those). The most essential dimensioning issue is to know the standing wave length -- which is dependent on the tube diameter. Probe should be 1/4 of that from the bottom (which should be flat) and minimum length -- I have seen stated -- is 3/4 of standing wave length, but preferably more. The diameter minimum/maximum is related to the wavelength again.

You find the calculators in various places. I have not the links handy just now, but please see Antenna FAQ links referring to waveguide/cantenna sites.

The tube must be well cdonductive (metal) from inside. Maybe PVC would do if you find a way to lace it with aluminium or similar? I would directly go for metal anyway.
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Postby MarkieUSA » Mon Sep 02, 2002 9:08 pm

HyperlinkTech
have the best selection on the web.
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