/diy/ - Do It Yourself

>>1538462
If you have an audio signal of amplitude N, you generate a sine wave that varies between +N and -N. So if your frequency is denoted by f and your audio signal is denoted by f(x), you're transmitting f(x) sin fx/2pi.
Then the receiver calculates the envelope, for instance by throwing away everything below 0 and computing a moving average.
Why does the filtering make it easier to utilize as power source?