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Dear LF,
during parts of most nights, the Luxembourg
crossmodulation shows a regular banding structure across a wide frequency range,
quite unlike the typical patterns of AM music modulation:
The band spacing matches
the subcarrier spectrum for "Mode A" DRM digital modulation (204
carriers spaced 41.66 Hz). A likely "heater" candidate would be Zehlendorf
177 kHz, which has been reported in DRM mode after midnight - could someone
perhaps confirm the times of digital operation?
Another "mystery" noise band sometimes appears
at night, about 200 Hz wide centered on 137.07 kHz, and of easterly origin
(red):
In this capture, there is also a weaker replica of
this band centered on 137.19 (north, violet). This combination would
suggest Luxembourg effect on both HGA22 (east) and DCF39 (north),
caused by a common heater carrying 1.64 kHz AM modulation. However I have no
clue to what the source is, and why it would carry such
an unusual modulation spectrum.
Kind
regards,
Markus, DF6NM
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