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ikarus1
Premium
join:2002-10-23
Urbanna, VA
reply to boomerbubba

Re: These Ducks Quack !!!

Click for full size
This picture is worth a thousand words about the focal point ...
--
»osiris.urbanna.net

Just Looking9

join:2002-02-09
Alexandria, VA

Hey, way cool pic, ikarus. Where'd you get it??
-johnmdesmond



ikarus1
Premium
join:2002-10-23
Urbanna, VA

said by Just Looking9:
Hey, way cool pic, ikarus. Where'd you get it??
-johnmdesmond
A gentleman named John Desmond mailed it to me. I'll put it on the site next week. He and I have been emailing each other for a few days. I don't know much about him, but he clearly understands optics and photography. He got it by putting a "slave flash down the hall behind a cardboard with a couple of slits in it."

It was so interesting, I've been in the garage all evening with a couple of laser pointers and some templates. It looks like all the templates pass muster -- BUT -- it is a whole lot harder to make a *REALLY* good one than I thought.

I'll be looking at simplification, with an eye towards improved accuracy in implementation because that focal point is *REALLY* important and it is too easy to miss it by a quarter of an inch.

You ... well... I did not read the sig till I posted.

-m-
--
»osiris.urbanna.net

[text was edited by author 2003-03-09 00:47:39]

Just Looking9

join:2002-02-09
Alexandria, VA

Mike: "Oh, a wise guy, ehh?"
John: "Nyuk, nyuk, nyuk *bonk* OWW!"

I just wish the implementation were up to the quality of the pix. My line of sight between the two (single-antenna) DWL-900AP+'s passes through one floor, one hallway wall, and two room walls at a 3D oblique angle (maybe about 5'x6'x15'). Resulting data rates:

1. with reflector - 2.02 Mb/s (megabit per second)
2. without reflector - 2.13 Mb/s
3. reflector backwards - 2.06 Mb/s
4. removed antenna - 1.74 Mb/s

Evidently, the situation has so much multipath, I'd be better off just walking around with a field strength meter to find a good site. (I guess this is what they mean by "hot-spot"!)

At one point I removed the antenna and covered the DWL with the dog's stainless steel waterdish. The whole thing was sitting on top of my steel-case computer with just path to air under both sides of the dish. I was still able to stream audio!

IIRC, the DWL actually does have a second internal antenna for diversity. It may have been ignoring my beautiful parabola at some points in the experiment.

-John

said by ikarus1:
said by Just Looking9:
Hey, way cool pic, ikarus. Where'd you get it??
-johnmdesmond
A gentleman named ...
...
You ... well... I did not read the sig till I posted.

-m-
--
»osiris.urbanna.net

[text was edited by author 2003-03-09 00:47:39]


latichever

join:2000-06-09
New Haven, CT

Anybody have real world experience with the parabolic antenna and 802.11a equipment? I have a Netgear HR314 router/access point. Love the throughput. Am disatisfied with the range. Would like to get consistent coverage on the second floor--AP on first floor where everything is fine--and get some coverage on the third floor.

Got a four pack of Pringles at the local BJs Warehouse with a dollar off coupon.

IMHO the key design issue is getting the cardboard or whatever is used to hold the parabolic reflector's shape and through which the dipole goes through. I've looked at all the pictures and am wondering if a thick piece of styrofoam could do this job. Anybody have any tips on this issue? Thanks in advance.

Am trying to avoid shooting up wires to the second and third floor of my house and/or not having to buy additional access points. Netgear is having a 50 dollar off rebate deal on their APs that expires 3-31, so I'm going to have build this and try it out before then.



boomerbubba

join:2001-06-15
Austin, TX

The parabolic design should work on the 5 Ghz frequencies without modification. Be aware that these frequencies are inherently more susceptible to attenuation in walls, etc., than 802.11b.

The dissected pringles cans should work fine, I think, with styrofoam. But if it were me, I would look first to the EZ-12 template on the FreeAntennas.com site. I haven't built it, but it really does look easy.