Philadelphia's new municipal wifi network kind of sucks, but I'm trying to give it a shot. I'm about 450 feet down the street from a lightpole antenna for the network. There are leafy trees all down the street. When I hang my wireless router out my 2nd floor apartment window (WRT54G with dd-wrt) it can just pick up the signal, but weakly and intermittently. DD-wrt reports signal strength no better than about -72, and it changes constantly. So I'm trying to figure out...
1. What kind of antenna should I use outside the window, or better yet, through the window? My WRT54G stock omni antennas with handmade reflectors barely pick up the signal. I tried using a prefab "Deluxe Cantenna" and it didn't help. I'm thinking that, because I'm trying to get signal around the trees, a directional antenna isn't the solution. From eBay I got really tall, supposed 9dbi replacement antennas for the WRT54G, and put on the reflectors, but that didn't have much effect either. I'm looking for a cost-effective solution - perhaps one of those Hawking corner antennas, to grab a focused swath of signal?
2. An alternative is to go on the 3rd-floor roof rather than through the window. I'm not sure yet if I have roof access, but if I do I'm thinking a directional antenna might help because it'd be above the trees. So then there's the cabling issue. To keep the antenna cabling short, I guess I'd have to put my router on the roof as well (in a sealed plastic box?) and then run an ethernet cable down the outside wall and through a window. That would mean leaving a router on the roof, and a window slightly ajar, through an east coast winter. And providing power to the router! (Argh.) I don't think a USB-wifi-stick antenna will work - I want to run my home network (a couple desktop computers and Vonage) off the line, using an ethernet-fed second router. What's the right way to set it all up?
I am somewhat surprised that a 9db antenna didn't really help as you indicated an signal of -72db. A standard WRT54G antenna is 3db so adding 9db would have given you a signal of -66. Is it possible to run your WRT in wireless B only mode. This improves sensitivity conciderably at the expense of bandwidth. You may get away with running your VoIP over this as I have done the same thing with my 2.1km link and I am running an Asterisk server at the end and I have no audible jitter (ping times <3ms). But remember that your WRT is a layer 3 router and therfore it doesn't transport VoIP well in the first place.
Thanks for your suggestions - I tried using just B and that may have helped a little. I'll keep experimenting. One problem may be that the 9dbi antennas aren't functioning as advertised. Also, the muni wifi signal seems to waver in and out, presumably due to the trees and distance. I'd like to try a more powerful omni or semi-directional antenna, without breaking the bank. Any suggestions for relatively inexpensive antennas in the, say, 12dbi-14dbi range would be much appreciated. Preferably commercially available antennas. Thanks again.
Yes defiantly use b, (once more Fred is the man!) you will actually get better throughput with less signal strength, I would probably go with a Yagi directional antenna, (so you can utilize any side reflections) Or a large parabolic and find a hot area in the trees.
Microwaves are absorbed by plants etc. (at 900Mhz you would have no problem).
Best thing to do is get above the trees if you can.
Municipal wifi antenna 
Linear Mode
