GeorgeF om...

Frank:
^ Each the first frequency in the set. It looks to me
^ like something interfered internally with the scanners,
^ but you said that the signal being received was data.

GeorgeF:
^ Without question it was some type of data.

In my limited experience the only thing that fits this situation is jamming.
I got to observe this being done by a very experienced jammer while my ship
was off the coast of Vietnam. High power noise at regularly spaced intervals
can jam an entire band.

A similar tactic is counter-jamming. I observed this same guy plug a teletype
into a common circuit and transmit useless data at high power. When the North
Vietnamese started jamming that frequency he transmitted the real data at low
power on another circuit.

So my revised guess of what you heard is that it may have been part a large
scale exercise in jamming tactics. Perhaps there was another unit involved
that was suppose to practice counter-jamming at the same time. If all nearby
frequencies were unusually quiet just before and just after the noise then I
would expect that it was a scheduled exercise.

Frank