Using wireless to get a fast connection where none exists

[Charles Steinkuehler]

Becker, Rob wrote:
> I have been trying to figure out how to get better than dial up access
> to a location that has no DSL or cable available.  The location is
> fairly high and probably has line of sight to areas that have DSL
> available.  Is line of sight absolutely required to get a wireless
> connection from one point to another?  I'm curious as to whether we
> could get a connection using better antenna's etc from a site with DSL
> to one without.  Does anyone have any experience with this?  What kind
> of range can you get with Yagi antennas and the like?  What kind of
> conditions are required for them to work?  Will a radio signal die off
> if it hits trees, or just be weakened?  Any help appreciated.

When a radio signal hits something like a building or tree, it gets 
attenuated and possibly dispersed (ie: weakened), not "swallowed up".

Probably the best way to get a 'real-world feel' for what happens is to 
compare wireless links to cell-phones (especially the more modern 
digital phones, which use somewhat similar frequencies).  They'll work 
through walls, inside metal buildings, etc, but the link quality will go 
to hell, and if it gets bad enough, they just won't work at all.

Remember the wireless LAN stuff isn't as powerful as the cell phones 
(and typically doesn't have a tower-mounted base-station with very high 
quality antennas on one end of the link), so don't expect it to work as 
well as a typical cell-phone without good antennas and maybe a power 
booster.

As a point of reference, I'm running a wireless link to my 'neighbors', 
who are 3 houses down (ie: two houses between us).  The wireless signal 
goes directly through *BOTH* houses, so the signal is definately not 
'line-of-sight'.  I'm running Linksys DWL900+AP's with the 'stock' 
antenna.  I did have to put a parabolic reflector on one end of the link 
(the other end is just the plain antenna), and I had to force the unit 
to stay out of the 22 MB/s rate or too many packets got dropped (I think 
due to multipath interfering with the fancier symbol coding used at the 
higher bit rates as higher-gain antennas didn't seem to help, but I have 
yet to borrow some real RF gear and verify that's really what was 
happening).

My advice:  Get some decent antennas, *SHORT* antenna pigtails, and go 
for it.  If you've mainly got line of sight and only have to go through 
a tree or two at one end, you'll probably be OK.  Note that there is a 
lot of loss in even the good antenna pigtails at GHz frequencies, so 
you're typically much better off to use a short pigtail putting the 
electronics near the antenna (properly protected from weather, if 
outside), and have long runs of power & ethernet, as required.

Oh...remeber 2.4 GHz is the frequency used by microwave ovens, due to 
the fact that it's energy is readily absorbed by water molecules

-- 
Charles Steinkuehler
charles at steinkuehler.net