Nano Nano wrote:
Could a device in theory record every channel simultaneously?
Yes.
Could it in practice?
Depends on what you consider "practical", I guess.
I would say "no."
Your typical TV or VCR has one or two "receivers" or "tuners" in it.
A receiver or tuner is capable of receiving or tuning a single channel
at a time, so a dual-receiver or dual-tuner TV or VCR is capable of
extracting two channels at once.
Software-defined "radio" (the same principles apply to receiving
channels on a wire that they do to receiving channels over radio waves
in the air) could, in theory, receiving the whole spectrum at once and
extract individual channels out of the stored data at a later time.
Again, it becomes a question of what you consider "practical."