[bobmcnamara]

Not exactly. All other parameters the same, the digital baud rate plays into how much bandwidth the signal uses, but not directly where it is in the spectrum.

Ex:9600 baud FSK signal centered at 440MHz still needs something capable of capturing around 440MHz, but this has nothing to do with baud rate. A 500MHz scope would do well for acquiring the signal.

Practically radios often divide the problem into two parts, first use a mixer to shift the signal down and filter out the parts you don't want, then decode the FSK which remains at a much lower frequency.

This is the governing limit: https://en.m.wikipedia.org/wiki/Shannon%E2%80%93Hartley_theo... and it considers things like SNR as well.

[KK7NIL]

I think the discussion has been all about high speed serial, so it's correct to say that the signal bandwidth starts at DC (or very close to it, there's often AC coupling) due to NRZ or PAM encoding.

[bobmcnamara]

Oh that makes sense!