Wireless connection to a remote station

[geoffrey mendelson]

On Jun 4, 2010, at 9:36 AM, Dan Shimshoni wrote:

First of all, wifi in Israel is heavily regulated. It's limited to  
100mw EIRP (radiated) power, so gain antennas, higher power  
transmitters, etc are illegal here.
If you use a gain antenna, you have to offset it by reducing output  
power or using a long feed line, which has a lot of loss, so it  
effectively does it anyway.
The one exception if the omnidirectional desktop and weatherproof  
antennas, which are not very much gain (3dbd) so it does not matter.

The first way to improve things is to use a desktop gain antenna on  
your router or at the PC end. Here's one I put on my access point,  
which I got from BUG. Note that it only improves signals 6db which is  
about 4 times. Most of that improvment is really phantom as the  
antenna normally supplied by an access point or router vendor is so  
lossy, you really are gaining back what you lost before with the bad  
antenna.

http://www.bug.co.il/prodtxt.asp?id=6357&perur=4

Antenna polarization is important. At the frequencies involved the  
loss due to the wrong polarization is over 20db (100 times). So keep  
all of your antennas vertical or horizontal.

You can legally "cheat" by using a real gain antenna if your access  
point or router allows you to use two antennas, one for reception, one  
for transmission.
Then you can use a high gain directional antenna for reception, which  
is unregulated, and a low gain omnidirectional antenna for  
transmission, which is.

Another way to do it is to move your access point to a spot closer to  
both computers, which may be tricky because it is not necessarily in  
the middle.
Paper, fiberboard (cheap furniture) and metal (including re-enforced  
concrete walls) absorb or block wifi signals, so sometimes moving them  
helps.


Adding another access point also helps, but it requries an ethernet  
cable between them. Every wifi router I have ever used supports this,  
you turn on bridging, turn off DHCP, and connect a LAN port to the LAN  
port of the other router. Make sure before you disconnect it during  
set up to assign it a fixed IP address on your network, or it will get  
lost or conflict with the other router(s).

It should be set to the same SSID, encryption type and keys, but a  
DIFFERENT channel. Any computer connected to your network will  
automaticaly roam to
the strongest signal. Make sure to use a unique SSID (obvious not  
default, siemens, attwifi, etc, and use it on all your access points  
that are connected together.

You can also use most routers, if you are tricky as Wifi adaptors (or  
just buy a gaming adaptor) so that could be used to extend the PC to  
the network. It does require an ethernet cable.

There are ways of extending a network wirelessly (look up MESH  
networks), Their big disadvantage is that the receive a packet of data  
and then retransmit it back on the same channel. This cuts your  
network throughput down to a third or so because not only does each  
packet get transmitted twice, there are delays built in to prevent two  
stations transmiting at the same time, so they are magnified too.

BTW, signals interfere with each other, so if you have any other  
transmitting device, whether its on the same channel or not, keep it  
at least a meter from any other. I found that on my Mac with a wifi  
CARDBUS card (802.11g) or the built in 802.11b card, I lost about 10%  
of the wifi signal if I had a bluetooth dongle plugged in. Moving the  
dongle to the far end of a meter USB extension cable fixed that problem.

I have 2 separate wifi networks, one 802.11b and the other 802.11g,  
and two DECT phone bases. The closest they are is about 4 meters  
apart, but the 2 wifi routers, and one of the DECT bases are in  
different rooms.

Geoff.
-- 
geoffrey mendelson N3OWJ/4X1GM
Jerusalem Israel geoffreymendelson at gmail.com
New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge  
or understanding, as in he has a sub-wikipedia understanding of the  
situation. i.e possessing less facts or information than can be found  
in the Wikipedia.