LF: Luxemburg effect?

["Dick Rollema" <d.w.rollema@freeler.nl>]

To All from PA0SE

Already several days I suffer from terrible broadcast QRM on the LF-band.
It sounds like Luxemburg effect centered on DC39.
It is so bad that this morning I could hardly read M0BMU on 137.4kHz
where I tried to measure his field strength and reporting back with my
1944 Hellschreiber. Jim always has a strong signal, about S8, and the
test failed completely due to the BC-QRM.
I experience it on both the Teletron LWF45 LF receiver and the W & G
SPM-12 selective level meter I used for the measurement. 
The LWF45 has excellent front-end selectivity (5 tuned circuits tracking
the local oscillator) so it can't be cross- or intermodulation  by a
strong BC-signal.

The only other cause I can think of is some "rusty bolt" effect
that has recently developed.

Do others have the same problem? 

73, Dick, PA0SE