Hi Peter,
Just a quick check you really need wifi access. We use Cirronet (now
Murata) modules at 2.4GHz for RS232 type communications and can achieve
that sort of range under open conditions. Output power is either +10 or
(about +18) dBm depending on our range requirement & etc. This using
standard "ruibber duck" antennae on hand held equipment.
The modules use frequency hopping and (presumably) error correction to
achieve the communications although we have had some degradation when used
in combination with some bluetooth modules.

Maximum data rate is 115200b/sec although I think there are other modules
that will work at higher bandwiidths.

But then, if you only need RS232 data rates, 433 or 900MHz modules may be
more appropriate anyway.

Richard P

On 12 October 2017 at 03:59, Van Horn, David <
david.vanhorn@backcountryaccess.com> wrote:

> I once did a wifi video connection between an unmodified USB wifi stick
> and another point, literally across the city of Pittsburgh.   The other e=
nd
> used a diversity pair of 12dB helicals.
> Radio mobile helped me choose the locations, and having a line of sight
> path worked wonderfully.
>
> Omni antennas will need to be high, and possibly with a little down-tilt.
> Foliage can be the end of your signal.
>
>
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