The only possible way to get 40 miles would be direct line of site using 2 very large, high gain directional dish antennas, with 1' of feedline to the modems. I assume they are using the 900mhz ISM band, which already has a lot of traffic and interference from cordless phones and other consumer devices. Very doubtful this would work beyond a few miles in a metro rf environment.
We use the Maxstream stuff for radio link on GPS telemetery units. I can tell you from experience that these units will operate over a line of sight link using 2db gain antennas well over 20 miles at 100mw, with data still readable at 40 miles+ At 1 watt we don't know how far they go because we've not been able to test beyond that.
I know, I did not think they would work that well either. Impressive stuff.
The whole line-up consists of the $60 Amps in-ears and $100 Tracks on-ear headphones, which both also come in slightly souped-up and pricier HD variations at $100 and $130, respectively.
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The only possible way to get 40 miles would be direct line of site using 2 very large, high gain directional dish antennas, with 1' of feedline to the modems. I assume they are using the 900mhz ISM band, which already has a lot of traffic and interference from cordless phones and other consumer devices. Very doubtful this would work beyond a few miles in a metro rf environment.
We use the Maxstream stuff for radio link on GPS telemetery units. I can tell you from experience that these units will operate over a line of sight link using 2db gain antennas well over 20 miles at 100mw, with data still readable at 40 miles+ At 1 watt we don't know how far they go because we've not been able to test beyond that.
I know, I did not think they would work that well either. Impressive stuff.
Tracks of these tests can be seen at http://www.gpsflight.com