Hello Mem,
If there is a another cheap way to use a transmitter that can be used in the woods for several kilometers would be useful. An Xbee is to expensive to use 8 ore 10 of these transmitter hosts. And to use 8 arduino pro mini's is also e very expensive. The receiver is at 100mhz its in the common fm radio range. So it wont have any effect mayby that you hear a single beep from a second in a radio program 
(happens all the time : )
It can be done with filters only beqourse i dont have inaf guts to make filters in electronics i wont do it that way. Programming is the best solution for me.
Thanks,
Christian