russotto
join:2000-10-05
Collegeville, PA
| Brute-force link
No advanced knowledge of antenna design was needed here. It was a brute-force "use a bigger dish" link. They used 10' (or 9.5', I've seen both figures quoted) parabolic dishes on either end. The cards they used were 15dBm Orinocos.
Assuming the dishes were 40dBi at WiFi frequencies (a reasonable guess, I think), the link was actually barely within FCC specs -- 15dBm transmit, 0 cable loss (the AP was mounted directly in the dish), 40dBi gain, for an EIRP of 65dBm. Using the 3 for one rule below 1W transmit power (30dBm) means they were allowed an EIRP of 36dBm + 15dBm*2 = 66dBm. So, amazingly, no violation of the FCC power rules.
The calculators at »www.zytrax.com/tech/wireless/calc.htm suggest they had lots of room left, too -- curvature of the earth would be a problem before the signal would fade too much. |
