1.3mi PtP link. Suggestions?

[Steve Mickeler]

I'm in the planning stages of a 1.3mi link. It's a NLOS situationdue to
some trees and rooftops.

I'm planning to use 2 x linksys WTR54GL units running DD-WRT.

Based on the following calculations, using a 2400MHz Tx frequency, the
1.31mi distance, along with a 200mW Tx power, -80dBm Rx sensitivity, 1dB
loss for connectors and cable, and 14dB antenna gain on the Tx and Rx, I
get a Theoretical System Operating Margin of 23.5 dB.

This is using a helical antenna, chosen because it is of a circular
polarization and according to my research, the best for getting through
and around obstructions.  Now I may be incorrect on this which is why I'm
asking here.

The antenna specs can be found here :
http://www.wade-antenna.com/Wade/Helical.PDF

Would anyone care to comment on this setup?