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[Ham-80211] diversity techniques and long link timing...

Chris D chriswlan2 at linnixislands.com
Fri Dec 16 09:59:11 UTC 2005


My first post... Hope I'm doing it right...


----- Original Message ----- 
From: "Frank" <kg6jve at pasadena.net>
To: "'TAPR Mailing List for Ham Radio Use of 802.11'"
<ham-80211 at lists.tapr.org>
Sent: Thursday, December 15, 2005 12:09
Subject: RE: [Ham-80211] diversity space or not


>
> The diversity on most of the less expensive gear does not do
"real"
> diversity. On the Senao and probably the Linksys, one port is
TX/RX and the
> other RX only.

I've always wondered about how the wifi gear does diversity... As
far as I know, each antenna must have its own receiver -at least
down to the "IF" section (whatever that is with wifi!). And then
some fancy comparator... Is that how it is done in wifi? Or do the 2
nodes test their single receiver on one antenna at a time, and then
just settle on the one with the best SNR? And hang on that
combination for...... the next... 5 minutes?


I've not found an advantage with having two antennas. I've
> used the Senao for links beyond 15 miles with 18dbi panel antennas
(one
> antenna on each end).

That leads to another question: I've read that most wifi has its
timing set for VERY short links and fast turnarounds... How do you
know that your units are indeed adjusted to expect a
"15-miles-delayed" response, and deal with it efficiently? Can most
cards be adjusted for unusual long link delays with some specialized
soft? Or is there a table somewhere that lists the timing for ea
model?

Just curious at this point.

Cheers.

Christian
wo1v






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