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The peculiar Luxembourg effect on the lower
sideband of HGA22 is audible again now at 16:40 UT. The heater source is clearly
639 kHz, it can't be 270 kHz as this one is currently
carrying different program contents.
The effect seems to be present only
within an hour or so around sunset, which might indicate that the
spectral asymmetry may be caused by an ionospheric anomaly around the day-night
terminator. Later during the night, all that remains is the "normal" symmetric
and lowpass filtered ICM.
This is truely stunning, just look and
listen!
Best 73,
Markus (DF6NM)
----- Original Message -----
Sent: Sunday, January 06, 2013 6:29 PM
Subject: LF: Re: Asymmetric Luxembourg Effect on HGA
The same Czech programme is also transmitted from
Topolná on 270 kHz, so that one would more likely be the heater. Interestingly
the crossmodulation source is almost twice the frequency as the victim. Well
almost, but not exactly - so that I still can't think of a simple physical
mechanism to explain the asymmetry.
Best 73,
Markus (DF6NM)
----- Original Message -----
Sent: Sunday, January 06, 2013 5:44
PM
Subject: Asymmetric Luxembourg Effect on
HGA
On the occasion of watching the LF band on
the Twente WebSDR, I noticed an unusual Luxembourg effect on the HGA
carrier 135.43 kHz. In addition to the "normal" ICM mumbling which is
muffled and symmetrical on both sidebands, the lower sideband carries a
relatively strong and wideband modulation. A quick listening scan of strong BC
stations shows that the modulation coincides with 639 kHz from Prag,
which is radiating 750 kW from a pair of 355 m high antennas. The
geographic constellation (Budapest - Prag - Holland) looks plausible for
ionospheric heating, but I have no explanation whatsoever for that one-sided
spectrum!
Best 73,
Markus (DF6NM)
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