sea communication - problem

hi, i have a problem about sea communication.

as show in figure, i want to make communication between two antennas. First antenna is over the sea, second antenna is over land or sea. between range of two antennas is 5 km.

according to you. Which frequency band can I use? Which is the best ?

The question is not what's the best, but what is allowed. As far as I know, there is part of band speciallz allocated for maritime use, but it is not exatly the same in all poarts of the world. Try searching google for "maritime frequency" or something like that.

Im guessing its a point to point link (transmitter and reciever at fixed locations)....
In that case you should make sure the Tx antenna is high enough for line of sight communication ( you have to account for the earths curvature), in case it is then use microwave link with a couple of directive antennas.

If you dont have line of sight, then use VHF Link (Terrestrial wave will get to the Tx even if there is no line of sight). The problem with this option is that you no longer have a point to point link, and you may cause interference with other systems.

First: Are you 10 miles from the coast ?. If yes, you can use any frequency you like ... Second: What kind of communication ?. voice. use PMR446 works perfect for your application. data ?. what speed ?..

use this calculator to calculate your line of sight for your antenna's.

http://homepages.nildram.co.uk/~vwlo...va/horizon.htm

Paul.