[MLB-WIRELESS] announcing cantenna gain ~ 7dB

[Roger Venning]

Gain pattern picture at http://users.bigpond.com/r.venning/wireless.html

I've still to do more on this, but for what its worth, it seems that a 
Harris Coffee tin (ID: 98mm) when used as a Cantenna (or more properly, 
a circular waveguide source fed by a quarter wave stub) produces a gain 
of 7dBi. The half power beam width is approximately 70 degrees. This 
means that you can be off target by about 35 degrees and still receive 
4dB gain over an isotropic (equal in all directions) radiator.

With Enterasys / Roamabout cards, 2dB of cable and connector loss at 
either end, a 11mbps link can be established over as much as 4km with 
these cans at either end. You can lose an additional 6dB in connectors, 
fade margin, knife edge line-of-sight etc. and still theoretically 
establish 11mbps link over 2km. Finally they should be good for 8km 
links at < 11mbps if you have ideal line of sight and suitably low 
interfering noise (this is absolutely best case scenario. If you need to 
go further than 8km then you will need to thinking about something more 
advanced. If you want a stable link that works through rain, fading etc. 
you will need a better antenna.).

Roger.

-- 
-------------------------------------------------------------
Roger Venning	\ Do not go gentle into that good night
Melbourne        \ Rage, rage against the dying of the light.
Australia <r.venning at telstra.com>                 Dylan Thomas





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