Wifi - can someone explain 'dbi' and 'mw' ratings?

[gotime]

I'm in search of a powerful wifi USB dongle or PCI card. I see all these products touting Xdbi and Xmw, I need to know at what point (if any) there is a fall off in reception ability. I'm looking at one on eBay with a 10dbi antenna and a 1500mw power rating.

Maybe I can just switch on a 10dbi antenna on my existing PCI card? THANKS

[socalblue]

Pushing up the power has little to do with the ability of end end device such as a laptop/PC to connect. It's a combination of channel, signal strength quality, interference, other devices & return path (materials, distance, etc.). You can get a better antenna but will the card actually drive the signal properly? Very few can.

In clear air pushing up the power & using a different antenna (Directional, etc.) can make a significant difference.

In most cases you will be better off moving away from 2.4 to 5 mhz & positioning the router/access point to a better location. If you are unable to do that change the PCI/USB card to a wireless bridge than can properly utilize a high gain antenna & connect to the PC via Ethernet.

[meaty-btz]

Wireless ANYTHING..
Noise Floor
Wattage
Return Power and Noise
Antenna Gain

Channels are Side-Bands

Noise floor is your base ambient noise at that frequency. If your signal strength is lower than the noise floor at the point of reception then you get no connection.

Boosting sending power is almost always a winning for one leg of the communication, but it is pointless if your return leg lacks similar power.

Increasing to a higher gain Antenna won't do much without also boosting the power. Otherwise you actually might lose sending power as you have more energy needed to saturate the Antenna to start the emitting. The higher gain Antenna will help with reception of attenuated signals that are still above the noise floor, however.

If you have a noisy frequency or one that fails to penetrate your structural materials well switch to 5GHZ from the 2.4Ghz (even the earth generates a ton of noise on this frequency). But in a two way situation like WiFi you need to have improvements to both to have reasonable effect so Higher Gain Antenna is good, most Internal and PCMCIA cards have crappy antenna's to begin with. Also you need to boost your wattage with an amplifier.

Wattage is Transmit Power Rating
Db is a measure of Noise and an analysis of the signal, noise included. Hope that helps.

[QuarterBoreGunner]

10dbi (Decibel isotropic)? How big is this thing?