I have some PICs communicating over a 900MHz wireless link in a camera
control system.  The base station has an omnidirectional whip antenna about
24" tall and the two remote stations have small yagis.  The remotes are
about 1.5 and 2 miles from the base station.  I have temporarily used 6"
rubber duck antennas on the remotes with good results.  The specs for the
modems puts the rage somewhere around 12 miles with yagis at both ends and
3-4 miles with whips.

I am using 1W Hummingbird modems from Xetron.  I think they are at
www.xetron.com.  The evaluation models that come with enclosures were
$850.00 each.  Antennas were about $150.00 each.  I have had these up for 2
years with no problems.  The modems can be set up for error correction and
can be set for point to point or multidrop.  They are available in RS232 and
422.  For OEM use you can get them cheaper without the enclosures.

There are cheaper modems available, but these are very good and reliable.

Tony Nixon wrote:

> Does anyone know of a device that can be controlled by a PIC to
> send/receive serial data over a radio link with a line of sight range of
> about 3KM max? Data integrity is very important.
>
> --
> Best regards
>
> Tony
>
> http://www.picnpoke.com
> Email sales@picnpoke.com