ready made boards available in the market
hi
u can get ready made fm transmitter boards for as cheap as rs 25
in india,u in pakistan convert it into its equivalent.for transmitting over
1 km u don't need to worry abt the reciever.only the current supplied to the transmitter unit is to be bothered abt.for 1 km dist 5 volts should suffice ,if the there is a direct line of transmission (straight line or else) u need to design circuits and enter into rf communication.
hope this is of any use to u.
bye