[amsat-bb] Funny rumbling noise on AO-51

[OZ1MY]

Hi all - mostly in Europe,
Since the need to use the 67 Hz, CTCSS tone is not
there any more, I have heard a funny "rumbling noise" on
the downlink.
That is mostly when the passes are to the West of me 
here in Copenhagen.
I have listened for the same on FO-29 - and it is there
as well. That is when adjusting my receive frequency to 
correspond to an uplink of approximately 145.920 MHz.

Can anyone confirm this ?

If yes - do you have any idea what it is ?

Happy New Year
73 OZ1MY
Ib