I often see the following strange occurrence on the spectrum display of my IC756 Pro 3.
The first telltale signs:
The normal low spiky grass display of the noise floor across the entire 40M Amateur band is replaced with a higher, almost constant value signal and its amplitude seems to vary, much like as a signal affected by QSB.
Tuning across the band one will normally observe what appears to be a normal strong signal as show below. However, tuning across the signal produces no audible signal at all, whilst using for example LSB mode.
Could this be spread spectrum signal?
The fact that the displayed noise floor is increased does it actually mask or obliterate weak signals? As weird as it may sound it does not seem to have a negative effect, but that still needs to be confirmed.
It would be great to see if the same situation is observed elsewhere in the world.