At 23:43 7/15/2005, you wrote:
OK, lets assume that they really could get line of sight
propagation. (They won't, but we'll assume that.)
Loss dB = 20 log(F) + 20 log(D) - 27.6, (F in MHz, D in meters)
1 mile = 1.609 km, so 192 miles = 308.928 km, We'll call it 309km for
fun.
My math says LOS path loss at 192 miles is 150 dB. and
that the 1st Fresnel zone is 320 feet.
Assuming they use a pair of 30dBi dishes, and a 1W amp at each end,
and get 300 feet above any obstruction (say, a valley floor), they might
make it, in terms of strict path loss.
Course, they have another problem. 'c' (the speed of light, in a
vacuum) is 299,792,458 m / s, so the propagation time is about 0.001
second
(1/1000 second, or 1 millisecond). 802.11's default CW(max) is 1023
usec, or about the propagation time *ONE WAY* (plus associated
serialization time(s), etc.)
So I seriously doubt that they get a working link @ 192 miles. If
they do, then it will be only because they're seeing an ACK (for the
original packet) for the 3rd, or possibly 5th or even 6th re-transmit.
Never mind that CSMA/CA is right out the window, given the slot time
of 802.11b is only 20 usec.
Jim
On Jul 15, 2005, at 8:00 AM, Frank Keeney wrote:
Update:
"Using USB WiFi cards and laptops that will be mounted to the back
of the
dishes and remote controlled we will attempted to make a connection in
excess of 192 miles at some point during the trip, whether it be in
Las
Vegas or Arizona where we plan to do addition testing and range
studies."
http://www.wifiworldrecord.com
ANNOUNCE: Third Annual Defcon Wifi Shootout Contest
Once again, wifi enthusiasts from around the globe will gather in
Las Vegas,
Nevada, July 29-31, 2005, to pit their geeky skills against one
another in
the 3rd Annual Defcon Wifi Shootout Contest.
With last year's contest winners establishing a new world's record
(certified by the Guinness Book of World Records), this year's
contest is
sure to once again shatter all preconceived notions as to how far a
wifi
signal can travel!
The goal of the contest is simple: to achieve the greatest
possible connect
distance between two 802.11b/g stations through innovative
engineering and
antenna design. Held in conjunction with the annual Defcon
conference,
teams will be drawn from the pool of approximately 5000 Defcon
attendees to
see whose wifi reigns supreme! Spectacular prizes and fun are
available to
all who participate.
For more information, and to view the results of last year's
contest, please
visit:
http://www.wifi-shootout.com
For more information about Defcon, please visit:
http://www.defcon.org
-----------
Thank you
Frank Keeney
Pasadena Networks, LLC
Antennas, Cables and Equipment:
http://www.wlanparts.com
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