[MLB-WIRELESS] New world record for wifi link (125 Miles).

Dan conhoolio at hotmail.com
Wed Aug 3 15:09:01 EST 2005

To do it with legal power levels I'd use the following:

A laptop at both ends running Linux - so you can run Kismet and HostAP.

A 200mW Senao card in each laptop.  The Senao cards have two antenna
sockets, one is TX/RX and one is RX only.  The 200mW Senaos have a better RX
sensitivity than the 100mW versions, and RX sensitivity is the key to
breaking this record legally.  We can separately pad down the TX level if we
have to.

The biggest dishes we can lay our hands on - one at each end plugged into
the RX-only socket of each Senao - this maximises our receive gain.  It also
makes our receiving beamwidth as narrow as possible - this cuts down on our
received noise level.

We could also possibly put an Amp in line with the RX antenna - since we
will not be transmitting with this antenna the amp will operate in RX-only
mode and we can amplify the received signal as much as we want.

A 13dBi antenna plugged into the TX/RX socket of the 200mW Senao.
200mW = 23dBm
23dB + 13dB = 36dB which is the max legal EIRP.

Possibly we could use a 14dB panel at both ends and claim a 1dB loss through
connectors and crappy cable. :)

Alternatively, a 16dBi antenna with a long enough run of LMR-400 to create a
3dB cable loss.  I don't think the beamwidth of the TX antenna is too
important as it is the RX antenna that has to sort the signal from the

Kismet will be very important for antenna pointing.  Since we will be
running a TX and an RX antenna at both ends we will need to line up each RX
antenna separately. Kismet operates by passive listening - without sending
out beacons.  So we can line up the RX antennas one at a time without
needing to have a fully symmetric link just to see each other.

Aiming the big receive dishes that have such narrow beamwidths will be
tricky.  They'd definitely need to be on a sturdy mount with precise
pan/tilt control.  Being up on a high mountain would probably mean lots of
wind so you'd need it anchored to something very heavy.

I have three 15 metre lengths of LMR400 that I can lend to such a
record-breaking attempt.  I also have two 25dB dishes that I could also loan
- but they aren't really the correct gain for this sort of thing.



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