cantenna experiments
in [Wireless Internet]
|
From: bjs555 on 6 Oct 2005 15:57 >Have you tried rotating the cantenna at all? Yes. Through 360 degrees. No luck. Hey David, just saw on one of your web pages that you tried a horn on the end of a cantenna. Sorry I called it goofy but it is funny looking. But then I read some posts by Jeff saying that a horn makes a smoother transition from the 50 Ohm radio source impedance to the 377 Ohm impedance of free space. Foot in mouth today. Everybody's a critic, huh?
From: bjs555 on 6 Oct 2005 16:43 >Polarity comes to mind. The can is three dimensional. You may have been >rotating the aziumth and elevation, but the orientation of the antenna >probe itself is also important. Try rotating the antenna on the long axis, >so that the probe is vertical, horizontal, and other points in between. >Especially if your small room is full of reflections, the optimum angle for >the probe may not be obvious. Tried that. Rotated slowly through the long axis 360 degrees. Picked up one ap but just barely. >I like the Windsurfer. I have made several. I keep forgetting to leave >enough "tab", so it takes me a while to assemble. >http://www.rahul.net/dold/clarence/EZ12-windsurfer.jpg Yeah, they seem to work great. > You can just make an antenna out of the end of the LMR195. Remove about 3 > inches of the plastic outer 'jacket' of the coax. Then pull the copper > braid back over the remaining jacket. Get a piece of brass tubing at a > hobby shop that will just slide over the braid and cut a piece of the > tubing to 32 mm. Trim away any excess braid. Cut the center conductor so > that it extends exactly 32 mm from where it exits from the braid. Very interesting. Thanks. I'm starting to think that the reason I don't see many aps is that the receive sensitivity of my Linksys WMP11 card isn't nearly as good as my usb dongle. It's an older card that I just happened to have lying around. But today I ordered more junk from Compusa and MicroCenter so I can LearnByDestroying (tm). Compusa has WUSB11s for $4.99 after rebate and MicroCenter has a usb dongle for $9.99, an SMC router for $7.99, and a Hawking antenna for $4.99 all after rebates.
From: bjs555 on 6 Oct 2005 17:52 I looked up some specs for my radios. The Linksys WMP11 receive sensitivity is around -82 dBm and the Zonet ZEW2501 is about -85 dBm. I take it this means I need 6.31 uW to get a signal into the Linksys and only 3.16 uW for the Zonet. Does that sound right? I think there's probably some variation these is in these specs from unit to unit but the lower Linksys sensitivity could explain what I see.
From: David Taylor on 6 Oct 2005 18:02 > Hey David, just saw on one of your web pages that you tried a horn on > the end of a cantenna. Sorry I called it goofy but it is funny > looking. But then I read some posts by Jeff saying that a horn makes a I didn't see your "goofy" comment but the novel part was that the whole antenna other than the rear and the N type connector and probe was all cardboard. :) It also happened to be the most effective antenna of the ones that I made. David.
From: bjs555 on 6 Oct 2005 18:11
Make that pW? Told ya I don't get along with logarithms. |