Ionospheric Modifications | The SWLing Post

Get it while you still can: The Luxemburg-Gorky effect

by 13dka

The Radio Luxembourg longwave transmitter Junglinster in the 1930s [RTL Group]

“In radiophysics, the Luxemburg-Gorky effect (named after Radio Luxemburg and the city of Gorky (Nizhny Novgorod)) is a phenomenon of cross modulation between two radio waves, one of which is strong, passing through the same part of a medium, especially a conductive region of atmosphere or a plasma.”

That sounds pretty abstract, right? In my own words, imagine your radio is tuned to a station on let’s say 162 kHz, 500 miles away. Somewhere in the middle between your receiver and the 162 kHz transmitter is a station transmitting on a different frequency, let’s say 234 kHz. The Luxemburg effect is that you can hear the modulation of the 234 kHz transmitter in the middle, on the 162kHz station you are receiving. The effect is not depending that much on the frequency/wavelength though, the longwave station could affect medium wave stations and it has been created using shortwave frequencies far apart.

It was observed first in 1932, when listeners of the Swiss Beromünster 60kW medium wave station built just one year prior also heard a bit of Radio Luxemburg’s longwave transmitter (250kHz) on the Beromünster frequency (653kHz until 1934). Of course this was assumed to be some kind of crosstalk within the receivers and probably drove radio engineers insane until 1933, when Bernhard D.H. Tellegen, a Dutch electrical engineer and inventor suggested the true origin of the effect: The new (1932) 150kW Radio Luxemburg longwave transmitter in Junglinster was directly modifying the ionosphere hundreds of kilometers above, it “heated” the ionosphere in a way that it made the plasma’s charge and reflectivity follow the amplitude modulation of Radio Luxemburg, thus modulating waves of other wavelengths crossing this part of the ionosphere.

Practical demonstration

Even if you’re living in Europe, you may never have witnessed that effect and according to this article by Paul Litwinovich, chances to observe this in the US are rather slim, due to the relatively low power of the stations. I’m in Europe but never noticed it either – until recently: Continue reading →

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The gas mixtures from NASA’s ionospheric experiment cause parts of the night sky to glow blue and green. (Photo: NASA)

Many thanks to SWLing Post contributor, Ed, who writes:

It might be interesting if you invited SWLing Post readers today see how NASA’s ionospheric experiment tonight (shortly after 9:00PM ET) affects RF propagation along the east coast:

http://www.smithsonianmag.com/smart-news/nasa-will-make-colorful-clouds-near-sunset-tonight-180963652/

I searched online to find any reference to this long series of NASA experiments affecting RF propagation, and found this 1980 paper:

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19810005401.pdf

…which contains this paragraph:

Ionospheric Modifications

The objectives motivating various experiments based on either decreasing or increasing the ambient plasma density by means of a chemical release include: (a) obtaining measurements of the rate of refilling after creation of a plasma depletion “hole” as a means of studying ambient ionization processes, (b) studying the magnetic field aligned propagation of VLF waves by creating a propagation duct, (c) simulating the formation and movement of the natural depletion “bubbles” which occur over the magnetic equator, (d) investigations of reaction rates, recombination coefficients, airglow production, etc., and (e) creating the conditions for inducing selected plasma instabilities to produce ionospheric irregularities and spread-F conditions. The science objectives in these experiments have a direct bearing on communication problems. Other forms of ionospheric modification are directed toward studying ionospheric/magnetospheric coupling and testing plasma theories.

So it might be fun to crowdsource from the SWL community to see if we can detect any propagation anomalies Tuesday night during this brief experiment. It’s unfortunate there’s not more time to coordinate different listeners monitoring different assigned frequencies. This reminds me of participating in ANARC’s “Woodpecker Project” in 1985 with 95 other SWL’s in 18 countries to determine the interference effects on HF broadcast from the Soviet Union’s use of Over-The-Horizon (OTH) radar in the HF bands.

I wonder how many SWL’ing Post readers participated in The Woodpecker Project and still have the nice “No Woodpeckers” tee shirt they earned for submitting their findings, which were combined into a final report that condemned the Soviets for causing interference on the HF bands.

Thanks for the tip, Ed! According to the linked article, the experiment will take place this evening, “soon after nine o’clock eastern time” (or 01:00 UTC).

This would be a great time to do an SDR wideband spectrum recording since you could possibly see any propagation effects on the waterfall display and play the event over multiple times. I’ve no clue if this experiment would yield any discernable results on HF, but it would be fun trying to detect it nonetheless.

Please comment if you plan to check out the experiment and/or if you were a participant in the Woodpecker Project!

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