[Cu-wireless] general update:

[by way of Illustrious niteshad <niteshad at whopper.de>]

One way to eliminate much of the complexity and expense incurred in our
currrent plan for Race Street would be to use high gain omni-directional
antennas.  Guerrilla.net has plans for a 10 dBi vertical collinear array,
unfortunately, their mathematical theory section is so full of holes that a fishnet
looks solid by comparision (e.g. they list the speed of light as 300000 m/s,
it is actually 300000000 m/s) With such basic errors, I do not trust their
numbers, or their expertise in physical/radio theory.  I am currently
scouring the ARRL Antenna Handbook for the proper theoretical underpinnings of the
vertical collinear array.  Once the theory is firm in hand, I could
probably build two of these antennae for between $20 and $40.  The primary
radiating elements are thin brass pipe and LMR-200 or LMR-400 co-ax cable. 
(ecommwireless sells LMR-200 for _$0.28/ft._!)  
	If we replace the 12 dBi Pringles Can yagis with 12 dBi omni-directional
(omni) antennas, we save cost on our network.  At each node, we need only
one wireless card, rather than 2 at Maiko's, 2 at Sascha's and 2 at Race and
Main.  According to my back of the envelope calculations, it will cost
approx. $944 to run wireless from Zach's to the IMC using weatherproof Pringles
cans, pigtails, free routers and $80 wireless PCI cards. (I assume that a
weatherproof Pringles Can costs about $12, the pigtails are known to cost $26).
	Using slightly more expensive omnidirectional antennas, the cost actually
drops to approx. $655.  This is due to the fact that only one antenna, and
thus one costly wireless card and pigtail, are needed at each node, rather
than two.  In other words, the more expensive antennas save us 30% of the
cost in the long run.  I should hasten to add that the $655 figure was arrived
at by estimating that the omni antenna will cost around $25 to build and
weatherproof, wireless cards cost $80 and pigtails cost $26.  
	While I favor the omni in theory, I realize that the goal is to get the
network up and running as quickly as possible.  Therefore, I suggest that we
attempt to move forward with the proven Pringles Can design (actually, we
might want to test the Coffee Can design, as it's simpler, cheaper and
inherently waterproof.)  If the collinear array proves itself to be superior in
performance, we can relatively easily replace the directional antennas with
omnis.  Then we can redeploy the directional antennas and surplus wireless
cards elsewhere in the community.  Possibly to people within line-of-sight of
our network who lack the income for internet access.  

best regards,

Mark 

-- 
Sent through Global Message Exchange - http://www.gmx.net