The Cellar - View Single Post - Calling Wi Fi Guru's

steambender · 01-06-2008, 11:52 PM

like TW said, 802.11 Wi-Fi runs at the same frequency as your home microwave. The earliest versions are designed to co-exist with it, as most microwaves pulse at 60Hz, half cycle, so 50% of the time they're off, and the network would use those intervals.

I don't know if 802.11g, etc sticks to that, or maybe new, stronger microwaves changed to full wave...I've also never compared the legal leakage levels allowed for microwaves to the typical minimum required wi-fi receive levels, I should, it might be interesting to know how much interference to expect.

As far as propagation, absorption and shielding...Wi-Fi wants to go in a straight line...it'll bounce off metal if you need to make a bank shot, but unobstructed line of sight is what you want, and never get. That's why antennas work better high up, just as already suggested - better line of sight.

...Wi-fi wavelengths are about 4", so they'll sneak through gaps in metal that are bigger than an inch or so. they'll get blocked by metal ducts, foil backed insulation or low e glass windows (often have a transparent metallic coating to reduce solar load). they should go around small pipes and wires. They get absorbed by concrete, ceramic tile, wood and drywall. they fade with distance faster than lower frequencies, all in all, pretty tender stuff.

my linksys wireless access point has two antennas on swivels. It uses diversity reception techniques by exploiting the fact that two independent paths will experience different scattering as they bounce around the house, and so one of the two should arrive in better shape...it's very effective for time varying impairments like people walking around. yes, your body. a big conductive sponge to Wi-Fi.

Sometimes it helps to make sure that the two linksys antennas are pointed at right angles (one vertical, one horizontal, or both at 45 degrees). signal path scattering is also polarization dependent, and the little rabbit ears are polarized linearly with their orientation. that diversity trick, again.

if the access point is at the end of the house in the basement(?) and the access point antennas are removable, for a few bucks you could try a directional antenna aimed at the rest of the house...why waste signal in a direction you're not using?

whatever you do, don't forget your tinfoil hat. double ply is best!

01-06-2008, 11:52 PM	#1
steambender It just needs a minor tweak...here... Join Date: Dec 2006 Location: kitty corner from where I grew up Posts: 48	Wi-Fi Propagation like TW said, 802.11 Wi-Fi runs at the same frequency as your home microwave. The earliest versions are designed to co-exist with it, as most microwaves pulse at 60Hz, half cycle, so 50% of the time they're off, and the network would use those intervals. I don't know if 802.11g, etc sticks to that, or maybe new, stronger microwaves changed to full wave...I've also never compared the legal leakage levels allowed for microwaves to the typical minimum required wi-fi receive levels, I should, it might be interesting to know how much interference to expect. As far as propagation, absorption and shielding...Wi-Fi wants to go in a straight line...it'll bounce off metal if you need to make a bank shot, but unobstructed line of sight is what you want, and never get. That's why antennas work better high up, just as already suggested - better line of sight. ...Wi-fi wavelengths are about 4", so they'll sneak through gaps in metal that are bigger than an inch or so. they'll get blocked by metal ducts, foil backed insulation or low e glass windows (often have a transparent metallic coating to reduce solar load). they should go around small pipes and wires. They get absorbed by concrete, ceramic tile, wood and drywall. they fade with distance faster than lower frequencies, all in all, pretty tender stuff. my linksys wireless access point has two antennas on swivels. It uses diversity reception techniques by exploiting the fact that two independent paths will experience different scattering as they bounce around the house, and so one of the two should arrive in better shape...it's very effective for time varying impairments like people walking around. yes, your body. a big conductive sponge to Wi-Fi. Sometimes it helps to make sure that the two linksys antennas are pointed at right angles (one vertical, one horizontal, or both at 45 degrees). signal path scattering is also polarization dependent, and the little rabbit ears are polarized linearly with their orientation. that diversity trick, again. if the access point is at the end of the house in the basement(?) and the access point antennas are removable, for a few bucks you could try a directional antenna aimed at the rest of the house...why waste signal in a direction you're not using? whatever you do, don't forget your tinfoil hat. double ply is best!