/diy/ - Do It Yourself

>>1769541
What you want is called a mixer; it multiplies the two signals together. There's a few different topologies, notably the diode ring mixer: a circuit that uses 4 diodes and a couple of transformers and usually has to be made by hand, and the Gilbert cell: a transistor-based circuit that you can buy in relatively cheap packages like the SA602. The SA602 and similar mixer ICs are small and have an optional built-in oscillator for connecting to a crystal of choice, and I assume they provide a relatively sinusoidal carrier wave, but they only really work at a particular input voltage range, so they can be fiddly to get going. Another option is a transconductance amplifier, which IIRC can be used as a mixer, but they're likely not suited to 10MHz operation.

Furthermore, if you want to transmit an audio AM signal, you'll need to include a DC component to the audio wave, otherwise you'll end up with a signal envelope of |f(t)|, pic related. This results in a carrier wave in between each sideband in the frequency domain.

Also it's easier to modulate and demodulate an FM signal if you just use a PLL, plus it's better for noise reasons.