The problem with noise is that your signal has to be bigger than the noise in order to be intelligible. Preferably you'd find a channel with less noise, not more.
Your signal doesn't have to be bigger than the noise. But your effective channel bandwidth is limited by the signal/noise ratio:
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Shannon’s channel capacity criteria for noisy channels
Given a communication channel with bandwidth of B Hz. and a signal-to-noise ratio of S/N, where S is the signal power and N is the noise power, Shannon’s formulae for the maximum channel capacity C of such a channel is
C = B log (1 + S/N)
(log is to base 2)
For example, for a channel with bandwidth of 3 KHz and with a S/N value of 1000, like that of a typical telephone line, the maximum channel capacity is
The hydrogen line (1420.40575 MHz) is the precession frequency of neutral hydrogen atoms, the most abundant substance in space. It happens to fall in the quietest part of the radio spectrum, what's known as the Microwave Window. Although there may not seem to be a lot of loose hydrogen atoms about (there's perhaps one per cubic centimeter of interstellar space), the interstellar medium contains a lot of cubic centimeters. So these individual atoms chirping away at 1420 MHz make a powerful chorus, which is readily detected by even small radio telescopes.
At 1420 MHz, even with an S/N of 1/1000, you'd have about 2,048 kbaud channel, if I'm doing my maths right. Given that an intentional signal could be highly directional, this seems possible.
