LF: Signals and voices (138.9 kHz)

[André Kesteloot]

Peter Bobek wrote:

> It is certainly not an IM in your receiving systems!  The funny thing is the
> signal on 138.9 is carrying a small amount of the program of the
> DEUTSCHLANDFUNK (freq. 153,0 and 207,0 kc).

This could be the "Luxembourg Effect".On pp. 36 of  "Propagation of Radio Waves
at Frequencies below 300 KC/s", Proceedings of the Seventh Meeting of the AGARD
Ionospheric Research Committee, Munich 1962, Edited by W.T.Blackband, Royal
Aircraft Establishment, Farnborough, England, we find the following remarks:

[When the ionosphere is heated by a high-power LF transmission, it behaves like
a plasma with non-linear electro-magnetic properties]:  "This [the Luxembourg
Effect] takes place when two electric waves of different wavelengths, one of
which is modulated and stronger than the other, meet in the same region of the
ionosphere, they interact with tee result that the modulated wave imparts a
small part of its modulation to the previous unmodulated wave.  The latter
therefore emerges from the ionosphere with a modulation which is called
cross-modulation or parasitic modulation. It is generally of the order of a few
per cent, but it becomes considerably greater if the carrier frequency of the
modulated wave is about equal to the local gyrofrequency (or cyclotronic
frequency)."

73
Andre Kesteloot N4ICK