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i'm looking for the most suitable modulation/demodulation method in order to transmit a message with 250Hz carrier and receive it correctly in presence of noise @60Hz and @180Hz.
Thanks
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you can choose any of FSK,ASK,BPSK,QPSK depending on complexity you accept. You start with bits (0,1), convert them to symbols (+1,-1 etc depending on mapping then scale up for DAC). You can choose your carrier at 250H (too low and I assume it is just some practice). As to noise @ specific frequency you need to explain that since random noise is everywhere so you need to tell what is nature of that noise or is it just interferer.