Yes Alberto, it sounds like the Luxembourg effect.

I have a heard a similar effect many times on DCF39's carrier. The high
tones of the modulation are attenuated, probably because of some
"thermal inertia" in the electron stuff up there.

73
Johan SM6LKM

----

Alberto di Bene wrote:
> LF group,
> 
>    tuning at 128.930 kHz, the frequency of the German power utility
> station, in USB mode,
> I can hear what is possible to listen to in this 30 sec. MP3 file :
> 
> http://www.sdradio.eu/audio/luxmbrg.mp3
> 
> Is this what is called the Luxembourg effect ? I hear a mix of various
> broadcasting stations
> in the intervals between the data streams. I used the mini-whip and
> Perseus, and strongly doubt
> that one of these components can be the cause of what otherwise could be
> attributed to intermodulation.
> Or, saying it better, it *is* intermodulation, but the responsible is
> the ionosphere.
> 
> Am I right ? Is that the (in)famous Luxembourg effect ? Or there is
> another reason for that ?
> 
> TNX
> 
> 73  Alberto  I2PHD