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For radio sistems narrow band (12,5 or 25 Khz)
-ASK. Simple and cheap (ususally AM systems)
-FFSK. Reliable and very good BER.
-PSK has a higher speed but perhaps is more dificult adjustment if you are using links betwen your diferent stations.
It is better for you study of a digital communication book.
I prefer you studying (digital and analog communication systems) by k.sam shanmugam. It contains tables that compares thease modulation techniques and you can find most of your answers in it.
The PSK modulation is the best talking about BER/Bandwidth. Of course is a little more complex than the other two (the implementation).
If you want that those modulations were "Continous Wave" Type, you will have a lot of more trouble implementing your circuits.
In other hand, you have the data transmition rate. If you want to do a low rate implementation, you can use a microcontroller to control some analog parameters of your circuit, to implement "complex" modulations.
FSK------Bandwidth Heavy....lower error probability....complex
ASK------Bandwidth Efficient....higher error probability (noise)....not much complex
PSK------Bandwidth Efficient....error probability increases as with no of levels (data rate)...very complex