[apochromat]

Narrow band? Hmmm.... Perhaps unfortunately for that approach, spread-spectrum may be a superior CW for many reasons, including efficient channel sharing and space-time signal demodulation i.e. turning multipath from a disadvantage into an advantage.

[jennyp]

Doesn't spread spectrum consist of multiple narrow band carriers, though? (I don't know.) Presumably a spread spectrum transmission would still look different than white noise?

[RadioAstronomer]

Narrow band? Hmmm.... Perhaps unfortunately for that approach, spread-spectrum may be a superior CW for many reasons, including efficient channel sharing and space-time signal demodulation i.e. turning multipath from a disadvantage into an advantage.

Indeed as we continue to cram more data into a frequency range, spread spectrum is the way to go. However, Radar and High-energy broadcasts are still required. Also if we spread out into the solar system, we will need hi power communications if were are to effectively communicate with many nodes. So a species may be noisy as radio develops, become quiet as the technology advances, and becomes noisy again as they expand into their solar system.