Hello LF,
last night, XGJ on 137.7798 was received here between 01:15 and about
05:30. There was also a weaker trace just below 137.7775 kHz,
presumably XKO. Both are visible on
http://freenet-homepage.de/df6nm/TA/TA_080325.jpg .
A while ago, Mike G3XDV asked about the possible impact of DCF-39
sidebands on TA reception in Germany. The strong magenta coloured noise
bands in my nighttime grabber screenshots are mostly caused by
ionospheric Luxembourg effects on the DCF carrier, whereas the FSK
modulation sidebands are weaker. Their rippled structure can often be
seen during the daytime, and is more pronounced when SpecLab's noise
blanker is switched off. Here at 310 km, its spectral density at 137.78
kHz is about 10 dB above quiet background noise. This includes
averaging over the typical 1s in 11s telegram duty cycle due to the
narrow FFT bandwidth. Slightly lower frequencies (137.775) look quieter
as we approach a minimum at 137.77 kHz. These gaps are about 10 Hz
wide, and they occur at multiples of the bitrate (200 Hz) from the DCF
space frequency (139.17 kHz).
Best 73
Markus, DF6NM
________________________________________________________________________
Bei AOL gibt's jetzt kostenlos eMail für alle. Klicken Sie auf AOL.de
um heraus zu finden, was es sonst noch kostenlos bei AOL gibt.
|
