From Steely Tom's explanation:
"They take the form of extremely rapid, swept-frequency pulses, lasting a few hundred milliseconds, and sweeping at a rates in the range of several megacycles per millisecond."
Would you consider "swept frequency pulses" to be "modulated" -- or would the sweep have to revere, as well -- to suit you?
reverSe...
Swept or only a tiny segment of emissions from a natural resonator which is spinning?
The most popular radar waveform is “linear frequency modulation”, LFM, in which the frequency increases linearly with time. For instance, the frequency of a one millisecond pulse might start at 3200 MHz and finish at 3201 MHz, increasing linearly throughout. This form of modulation gives you the energy of a one millisecond pulse, and the range resolution of a one microsecond pulse.
Thanks. It sounds as though they COULD be the work of intelligent beings. Next question: Since we know the planets and stellar bodies give off musical sound; what else out there could do that, and sweep the frequencies? You’re the scientist. I’m just a dumb farmer, but very curious.