Topband: Odd background Noise

[Charles Bibb]

Hello, All

As most topbanders are no doubt aware by now, last night was a night 
of exceptional propagation on 160M!
(and 80M, too.)  Hopefully we will have more of the same tonight and 
tomorrow night during the CQ 160M
contest.

Rather that re-hash the activity of the rare DX that appeared last 
night, though, I would like to ask if anyone
else was hearing the odd background noise that I was.

It is hard to describe, but I'll give it a try.  It is not loud, I 
could only hear it when tuned to a spot on the band
that contained no signals (hard to find last night). It sounds sort 
of like the chugging of an idling diesel
engine, only at a high pitch, not that low throb. It sounds like the 
rise and fall of ionospherically propagated
background noise with a peak-to-peak QSB period of about 3 to 5 
Hz.  That is to say, I was hearing a slight
noise peak about 3 to 5 times per second.  Along with this 
phenomenon, the band was, in general, much
quieter than normal.  I also heard it on 80M.  I've heard it before, 
but only when the band is very quiet and
conditions exceptionally good for long-haul DX. It does not mask or 
make DX signals any harder to copy.

Did anyone else hear it?  Does anyone have any idea what it is?  Is 
it coming from the upper reaches of the
ionosphere?  Or, is it coming from space?

Ideas, anyone?

Charles - K5ZK