Jim/Gene:
Another list member sent me this useful path design utility for the AirMax
product but appears useful for other systems.
https://airlink.ubnt.com/#/
> "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."
My main interest with two systems is help with "lightning damage diversity."
Ideally, I would like to keep one system up and running in the event the
alternate hardware fails up the tower.
You raise an interesting point though about using H-POL for one link and
perhaps V-POL for the other. In a prior life, I designed a 23 GHz system
that way. At 23 GHz, Fresnel ground clearance wasn't even a design factor.
Rain attenuation was. During the FL summers, a 2.5 mile path was lost
nearly every afternoon.
Paul, W9AC
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Jim
Lux
Sent: Thursday, October 22, 2015 10:44 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] LPFM STL
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.
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