You might be able to modulate the transmitter on some modules but the receivers are not designed for analog usage. There may be some modules hat work to some extent but most wont work at all.
You can't convert the analog to digital either, their bandwidth and data rates are too low.
ok...can you suggest a simple method to transmit voice in a 250+ metres,in bi direction. I am making this to benefit a group of school students.pls help.