[TowerTalk] LPFM STL

[Jim Lux]

On 10/22/15 6:42 AM, Paul Christensen wrote:
> Paul,
>
> I am looking into a high power Wi-Fi solution to get our remote site off
> DSL.  The footprint edge of the Jacksonville-Comcast Xfinity service area is
> approximately 10-12 miles away.  The idea is to install a wireless site at a
> Comcast subscriber location.
>
> Any idea of the maximum expected LOS distance when running these units at
> full power?  We can get the Wi-Fi antenna at the remote site as high as 140
> ft. AGL.   Possibly two units would be installed, one at a lower height for
> "lightning damage diversity," then switch between the two on the ground.
>
> Paul, W9AC
>

It's on a tower, and relevant to ham applications, so I suppose it's 
legal grist for the list..

What kind of antenna are you thinking about for the WiFi? and What band?

29 dBi antennas for 5.8 GHz are about $70, same size antenna is about 
24dBi for 2.4 GHz band. These are the "barbecue grill" looking ones.

Are you thinking about polarization diversity? There's a fair number of 
dual pol antennas available, although you could just bolt two of the 
cheap grid antennas on, 90 degrees rotated from each other.

A back of the envelope for 2.4 GHz seems to show that with 24 dBi 
antennas on both ends of the link, and radiating 100mW, you've got about 
-60 dBm into the receiver. That seems like a lot of margin for WiFi. I 
didn't allow for cable loss, antenna mismatch, etc.

I also don't know if 100mW into a 24dBi antenna will be too high for 
Part 15 EIRP limits.



You'll need to calculate Fresnel zone distances to make sure you don't 
pick a "bad" height. Curvature of the earth means you'll need to be at 
least 20 ft high.