>I'd like to cover at least 50 Km (that is a little over 30 miles), so I
will
>need a fairly powerful transmitter...
>
>Andres Tarzia
>Technology Consultant, SMART S.A.
>e-mail: atarzia@smart.com.ar
>
That is going to be a problem.  Most commercial pagers work on a cellular
basis: various transmitters transmit the message at the same time from
various locations. These fairly strong  transmitters are locarted on high
buildings or hilltops to improve coverage. If you want to have good coverage
indoors and outdoors in an area with a radius of 50 km you are roughly
looking at a vhf transmitter of 40 W or more  with an antenna at a hight of
25 - 30 meters (very roughly) in flat country.  Exact fieldstrenght
calculations would be necessary. Also depends on the transmitting frequency:
the higher the frequency the more power you need for indoor reception. The
values given are based on the 144-1448 Mc amateur frequencies and experience
with amateur repeater stations. In mountainous country it would be
impossible to do without one or more repeater stations.
Henk Tobbe - VK2GWK(PA0ADC)