Dear Uwe,
here is what I fugured

wx- condx: surface wet snow 1 - 2 cm.
Antenna: Umbrella 20m, top 300 pF,
R/in = 24 Ohm
RX: Praecitronik MV 62
locator: JO40LE

Time  ur signal noise          DCF39
2200  -86 dBu  -89,5 dBu  ---------
2214  -76 dBu! -90 dBu   -26.5 dBu
2221  -81 dBu  -90 dBu   -30.5 dBu
2227  -87 dBu  -90 dBu   -34.5 dBu
2231  -83 dBu  -90 dBu    -----------
That's more questions than answers, I'm afraid.
Regards, vy 73 es gl de Peter, dj9dw.