LF: Fluctuating background noise

["Dick Rollema" <d.w.rollema@freeler.nl>]

To All from PA0SE,

When looking for VO1NA using SPECTRAN I noticed that at some moments the
background noise more or less suddenly decreased and then Joe's signal
became visible. The low noise leven was restricted to a narrow band of a
few Hertz wide. 
Has this been observed by others?
Because it occurred in such a narrow frequency band I think it may be
caused by selective fading within the noise spectrum.  And if so may
we conclude that the noise arrived via space wave?
Hw?

73, Dick, PA0SE