O'Reilly's Antenna Shootout

nickynicky9doors writes: "From Rob Flickenger O'Reilly Network's Systems Administrator : 'Gregory Rehm hosted an Antenna Battle Royale between a Lucent popsicle stick, a couple of Pringles Cans, our Coffee Can, a Hunt's Tomato Sauce can, and a 40oz can of 'Big Chunk' beef stew. Who was the winner?'" Let's just say it doesn't come loaded with saddle-shaped styro-chips.

a dish?

[itzdandy]

might one of these antenas be mounted in reverse, on a small DSS/primestar style dish to improve reception?

just place the end of the pringles can at the focal point of the dish? i would suspect a significant gain from this, but then again the whole point of a pringles can antena is to be cheap, how cheap can a person get a dish?

also, what do you suspect the range to be on one of these homebrew antenas? could it span 2 miles to a passive repeater, then two more miles? or would the repeater have to be and active 802.11b access point?

if i were to hack an 802.11b access point to install a pigtail for a homebrew antena, could i install two pigtails for two antenas? and would it be advisable to further hack the accesspoint to boost the signal to 80-90dB?? i believe the FCC limits these 2.4Ghz signals to 100dB, but dont quote me on that.

Re:a dish?

[Phork]

You could use two antennas, but it is not as simple as connecting the wires, you need to use a 2 to 1 RF transformer meant for 2.4ghz, but there are plenty of these devices made these days because of the proliferation of 2.4ghz devices. I see them advertised in rf design all the time.

What they need to try next is a yogi.

[ubiquitin]

That's right, not a yagi but a yogi antenna. It is similar to a yagi (classic unidirectional antenna) but has logarithmic descending elements. In a traditional yagi antenna, all elements in the array are the same size/shape.

I hooked one up to my TiBook via a hacked-together pigtail and lucent/orinoco connector to avoid the weak internal TiBook antenna, and got about 12 dBi out of it, this with no external power. For some yogi antenna info, see: www.ve3gk.com/stacked.htm [ve3gk.com]

I've seen this done before..

[Entrope]

But with slightly different subject matter, and a different set of suckers. See here. [northwestern.edu] It's amusing to see this kind of hoax fool people.

Re:Serious question

[SectoidRandom]

With the computer in the attic, there is a far better way of doing it, although slightly more expensive. Use an access point (such as LinksysWAP11 / SMC2655W) with power over ethernet, place the AP in a weather proof box, with just the CAT5 connection to it, screw that to your antenna mast (or base if it) and your set. See 1km 802.11b in Egypt [d128.com] for some nice pictures of it.

For cost I guess if your just doing ptp links it is going to cost more, but not that much really, at least here in Australia excluding the cable savings, PoE adaptor, etc, an AP such as the Linksys or SMC can cost less than $450, (mine was $420 cost price) a standard Wireless PCI card will cost at least $300.

Re:Your numbers are a bit off

[Lumpy]

Yeah, math at 3am creates foggy thinking and everything is off by one decimal point. Which also skewed my antenna gain calculations... I was including the gain of the feed-can in the antenna dish gain... effectively tripling the gain numbers.

Yes some have calculated a 22dbi gain from a promestar dish but that is a rarity. It's actually closer to 12-14 in normal attempts with tuning and finer adjustment it creeps toward 20dbi and a 7 foot dsh will give you approx 20-30 dbi with an awesome noise floor and off axis rejection. Arrgh.. I multiplied the dish gain by the feedhorn gain... which giving nice numbers caused some electromagnetic impossibilities.

Simulate the antenna first

[LM741N]

On my web site http://www.pythonemproject.com there are some FDTD Python programs that you can use to simulate waveguide antennas. Now these are not GUI based, and there is a learning curve. You basically set up the metal so that its tangential E fields are 0, thats called PEC, perfect electrical conductor. Each bit of metal corresponds to a matrix element. I've been meaning to try out a slotted waveguide antenna on one of my programs, maybe I will get to it and post it there. All of the FDTD programs are GPL, and you can use Animabob to view the E fields in real time.