lekkala wrote:
Yes I want to send one bit of binary information.If it is more than one
bit also no problem.
Which type of transmitter and receiver i can use for sending one bit
or one byte of information from sender to destination. The distance
between sender and receiver is 2 Km.

Sound from an air horn will carry that far. It would help to
know more about the application.
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73, Cecil http://www.w5dxp.com