[MLB-WIRELESS] Cisco tool

[Luke Schapel]

Came across this the other day, maybe you can't just point and shoot!

http://hydra.carleton.ca/articles/ve3jf-dcc97.html

Luke Schapel


Jason Hecker wrote:
> 
> With regards to the Cisco spreadsheet posted on the site, it's pretty
> damned nifty.  The 10dB fade margin is a very good idea and there for a
> reason, namely effects from the atmosphere (rain and fog) and dynamic
> multipath (this will change as reflections come off moving cars, trees,
> atmosphere turbulence, microwave ducting in moist warm air, planes) which
> can degrade the performance by up to 10dB.  This sort of thing can be
> improved if you employ space diversity.  If you have a card with 2 antenna
> connectors, like the Senao EXT2 device, and you space two antennas spaced
> apart (I forget how many wavelengths it should be), in receive mode it will
> pick the best antenna for signal strength because it has a 'voter' in it
> which decides which antennas has the best signal.  The one and same antenna
> will always be used for transmitting as space diversity is only useful when
> receiving.  If you do this then your fade margin is reduced.
> 
> I would suggest that for backbone links, space diversity is used for
> maximum reliability.  If the signal is too weak the cards will drop to a
> lower bitrate to compensate.
> 
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