Ellen MacArthur wrote:
Thanks, Gilligan. Your a dear. I don't understand all that technical stuff. Decibels are for
sound waves. I just can't figure out how they apply to radio waves when you can't even hear
them. But I just ordered one of the antennas. Anything's gotta be better than the weak little
antenna inside my laptop. Should I set the rate inside the card driver properties at 1 Mbps to
make it work the best?

Cheers,
Ellen

Please let me know how it works out.
I need to tap into a wi-fi network here.

Thanks
Joe


"Gilligan" wrote
|
| "Ellen MacArthur" wrote in message
| reenews.net...
| http://www.radiolabs.com/products/wireless/waverv.php
| I'm looking for a good antenna for wifi on my RV for a laptop computer.
| What do you think of this one?
| It's got all the technical things there. Do they look good? Can it really
| reach out four miles like it said in Cruising World
| magazine?
|
| Cheers,
| Ellen
|
|
| They put the radio modem under an 8 dB omnidirectional antenna and run the
| data signal down the USB cable.
|
| One way link budget:
|
| Tx power = +26 dBm
| Tx gain = +8 dB
| Rx gain = +8 dB (assume receiver is same as Tx)
|
| Receiver sensitivity = -93 dBm @ 1Mbps data rate.
|
| Link can tolerate path loss of 26 +8 + 8 -93 dB = 135 dB
|
|
| Friis Equation:
|
| Path loss (dB) = 32.44 + 20 log (km) + 20 log (MHz)
|
| PL (dB) = 32.44 + 20 log (km) + 20 log (2450)
|
| PL (dB) = 100 + 20 log (km)
|
| 135 - 100.22 = 20 log (km)
|
| 1.73 = log (km)
|
| 55 km = Link range.
|
| I think their quoted sensitivity of -93 dBm may be too high. For a 1 Mbps
| data rate assume a slope factor of 2.3 so Rx bandwidth is approx 2.5 MHz.
|
| Thermal noise power at 273K is:
|
| P = kTB k = 1.38e-23; T = 273; B = 2.5e6 Hz
|
| P = 9.5 fW
|
| P = -110 dBm.
|
| Doesn't look like thermal noise is a problem. The noise figure of the front
| end is probably 2-3 dB so it should go 4 miles and beyond.
|
| Go for it, you can always return it if it's a pig.
|
|
|
|