Luxemburg–Gorky effect

Lore & Background

Current theory holds that the conductivity of the ionosphere is affected by the presence of strong radio waves. When station 'A' radiates a strong amplitude-modulated signal, some of it modulates the conductivity of the ionosphere above the station. If station 'B' sends another amplitude-modulated signal from a different location, the part of station 'B's signal that passes through the ionosphere disturbed by station 'A' may have its strength modulated by station 'A's signal, even though the two signals are widely apart in frequency. The ionosphere thus passes station 'B's signal with a strength that varies in step with the modulation of station 'A'. This re-modulation level is usually only a few percent, but it is enough to make both stations audible. The interference disappears as the receiver is tuned slightly away from the frequency of station 'B'.

Reader's Guide

The Luxemburg–Gorky effect illustrates a fundamental interaction between radio waves and the ionosphere, where a strong signal can imprint its modulation onto another signal via changes in ionospheric conductivity. This cross-modulation phenomenon has implications for understanding radio propagation and interference in the medium wave and longwave bands. It highlights the nonlinear behavior of the ionosphere when subjected to high-power transmissions, a consideration for broadcasters and communications engineers. The effect also connects to broader topics in plasma physics and distortion, as the ionosphere behaves as a plasma whose properties are altered by incident electromagnetic radiation. Although the re-modulation level is typically small, the effect demonstrates that even widely separated frequencies can interact through the ionosphere, complicating reception in regions where multiple strong signals are present. The phenomenon remains a classic example of ionospheric nonlinearity and is referenced in studies of radio wave propagation and plasma interactions.

Did You Know?

• It involves cross modulation between two radio waves, one of which is strong, passing through the same part of a medium.
• The re-modulation level of the station B signal is usually only a few percent.
• A paper by Dario Graffi proposed a theory of the Luxemburg effect based on Volterra's theory of hereditary phenomena.