Build your own free space optics data link

erol · 22-04-2004, 17:55

In case anyone is interested

http://ronja.twibright.com/

altis · 22-04-2004, 19:01

Good idea but I suspect that wireless is cheaper and faster:
http://www.frars.org.uk/cgi-bin/render.pl?pageid=1066

erol · 22-04-2004, 19:32

Quote:

Originally Posted by altis

Good idea but I suspect that wireless is cheaper and faster:
http://www.frars.org.uk/cgi-bin/render.pl?pageid=1066

certainly it has distance advantages and point to multipoint advatages and possibly cost advatages as well.

however wifi also has it's disadvatages. For a start the 11mbs (for which you need a _good_ signal) give a throughput nearer 5mbs in reality.

interferance issues are another disadvantage

As far your link goes - I am sure they were not operating within the UK legal limits of 100mw EIRP. You just can not get that sort of range within 100mw EIRP - at least as I understand it.

For me affordable (read - build your own) free space optics complement wifi / wireless and wired options for community / self built networks and as such I welcome the ronja project.

Now all I have to do is find someone willing to build me one

altis · 22-04-2004, 20:16

Yep, the radiated power limit defined by ETSI is 100mW EIRP (or +20 dBm). I think that applies across the whole of Europe. Because, in America, they define the transmitter power instead, the limits are effectively much higher. Some details here:
http://www.cisco.com/application/vnd...00800a912a.xls
http://www.cisco.com/warp/public/102...re-us-calc.xls

erol · 22-04-2004, 20:33

Quote:

Originally Posted by altis

Yep, the radiated power limit defined by ETSI is 100mW EIRP (or +20 dBm). I think that applies across the whole of Europe. Because, in America, they define the transmitter power instead, the limits are effectively much higher. Some details here:
http://www.cisco.com/application/vnd...00800a912a.xls
http://www.cisco.com/warp/public/102...re-us-calc.xls

OFCOM is currently looking at increasing the limits for outdoor use in rural / remote areas (200mw has beem suggested)
Also it's worth noting that 5.8ghz band C has an outdoor limit of 2w - though there is a 'light licensing' requirment to use this and compliant kit is a bit thin on the ground right now