I am thinking of puting together one of these cheap, homemade directional wireless network antennas. Its basically a tin can and a cable - and is supposed to give you ~13dBm !!!
Has anyone made one of these homemade antennas?
What did you think?
Any chance it would wreck your wireless equipment (wirless router in my case)?
It would be great to hear your thoughts even if you have not made one of these.
OK, Color me ignorant. This antenna is for computers? Radios? I read the attached
page, but it wasn’t too clear, or am i just not computer geeky enough?
It’s for computers to wireless connect to a network.
I can’t see that it would do any harm. It’s just a fancy piece of wire that pig tails onto your regular antenna.
Now they tell me! I just dropped $50 on a directional antenna as my Squeezebox needed just a little more “oomph” in the signal. <grumbles> On the other hand, I’m not sure a big soup can would have been welcomed into the living room.
On the router / AP side, does anyone know if it makes a difference on which antenna is changed? My Linksys WRT54G has two antennas. Asking Linksys was futile:
Huh? They screw onto the router as you would the cable to a TV. Needless to say, they didn’t tell if there was a difference between the left and right antennas. ie: Is one “B” and the other “G”?
Forget about the Pringles can and it’s derivatives - they’re worthless. They aren’t “Yagi waveguides” - the only gain they get is a bit of reflection off the can bottom, and it’s a bit small even for that.
The soup can is better - it has almost the proper dimensions to be a 1/4 wave reflector. I built on and got ~10dbd (12dbi) out of it.
The best you can build uses a Pepperidge Farm Pirouette can and duct adapter.
If you need more gain than that, you’ll need a flat panel or grid antenna, depending on your application. Look for one with a high front-to-back ratio, as this will help reduce interference from other wireless networks.
Note that putting a high-gain antenna on a commercial router might void the warranty even if you don’t have to open it up to do so - those are sold as FCC Part 15 systems, and changing the antenna means they aren’t licensed any more. But as long as you don’t go and do something stupid like put a 4W military amp on a 30dbi grid and post pictures to Slashdot, you’ll be fine 
Probably not if you do it right. If the Standing Wave Ratio of the antenna is off, or the impedence is wrong, you could burn up the radio, but you’d have to be pretty far off the specs for that to happen.
No difference, but if you change one of the antennas, take off the other. If your firmware supports it, change it from “diversity” mode to “single antenna” - you might need to look for hacked firmware to do this. I know some of the Linksys routers can be upgraded with non-Linksys software to give extra functionality, but I’ve never played with the WRT54G.
Also, if you need a lot of gain for a long-distance link, check out Trevor Marshall’s page on using an old PrimeStar dish to get 27dbi or more.
Wow. Thank you very much SteelWolf. That was really helpful. I like the Pirouette can link.
I will go ahead and make one of these this weekend.
Will also have to get myself listed in the local wireless network - looks like a brilliant concept.
Slightly off topic, but - are you building a wireless bridge? a network link between two wireless access points? I mean, why else would you want a very directional antenna?
Because, I thought about doing that to network my barn to my house (the barn is the only place on my wooded land with a view of the southern sky, where my broadband satellite is).
But I have an old CATV cable buried between house and barn, and I piped the wireless signal through that. So it isn’t literally wireless anymore. No antennas - the wireless access points just translate between Cat5 ethernet cable and 75 ohm coax. I’m communicating through it right now on SDMB.
I have a broadband cable modem – wireless router – cat 5 to PC in one building.
I want to be able to aim the wireless router, using the cantenna, to a second house on the property to be picked up by a laptop and another PC, both with wireless network cards. The omnidirectional signal just doesnt make it.
I’m on the verandah of the house right now tapping away at my wireless laptop on the SDMB.
Also it would be good later to connect to the community wireless network here in Sydney. But I suppose that requires a good omnidirectional antenna - $400 ouch. Or I could point the cantenna to a network node and either hope that the other laptop can still see it or rotate the antenna between the two as required.
An update…
Using the link provided by SteelWolf I built a directional ‘cantenna’ and it has been working perfectly for a week.
The signal still has to go through a tree and a wall, yet it is still strong - transmitting at 11 Mbps. Previously I couldnt get a thing.
I ended up using a 114mm diameter can, 240mm long - used to package bottled chemical in vermiculite - which was a very convenient size.
Made some good brackets and stuck it on the end of a curtain (hopefully not lightning) rod mounted to the facia board. The cantenna connects to the router via a 3m cable with a N connecter.