Atmospheric broadcasting

[Steve Byan]

On Jul 27, 2006, at 7:39 PM, Charles Bacon wrote:

> I came across the following announcement today from the New Scientist.
> Wonder what this would do to ham radio?
>
>
> Atmospheric broadcasting
>
> The layer of the atmosphere known as the ionosphere, at an altitude  
> of 50
> kilometres, is already used as a radio reflector, bouncing low  
> frequency
> radio signals from one side of the world to the other.
>
> Researchers at Samsung in Korea are now working on a way to turn the
> ionosphere into an antenna. A patent application filed by the company
> reveals plans to direct higher frequencies radio signals, at about 1
> gigahertz, at the ionosphere, to alter its behaviour.
>
> It describes using an Ultra High Frequency (UHF) radio signal, of a  
> few
> hundred megahertz, and a carrier signal of around 1 gigahertz. The  
> mix would
> be amplified and focused by a dish into a spot beam that hits the  
> underside
> of the ionosphere.
>
> The idea is for the GHz carrier signal to be absorbed by the  
> atmosphere and
> for the UHF one to alter the temperature of electrons flowing  
> through the
> ionosphere. This should create an alternating current within the  
> ionosphere
> that can be modulated at a particular frequency. The target spot  
> should then
> work as an antenna, radiating the UHF tens of kilometres back down  
> to Earth.

Sounds like an application of the Luxemburg Effect.
 From <http://lope.ece.uiuc.edu/history.htm>:

There is a very interesting ionospheric phenomena, the Luxemburg  
Effect, that was exploited in the early days of the laboratory and  
was a precursor of many perturbation techniques now used in many   
fields. Telegren was the person who discovered the effect, namely  
that  Radio Luxemburg would heat the electrons in the ionosphere and  
thus  transfer the audio envelope on its signal to any wave  
traversing that  portion of the ionosphere by modulating the  
absorption. Prof. Goldstein  exploited and expanded this phenomena in  
the laboratory to identify and  quantify many electron temperature  
dependent processes such as e-i recombination, electron-ion collision  
frequency, and any other electron  collision process. He used to  
microwave signals, the "heating"  wave and the "sensing" wave to  
examine these processes in the  decaying portion or "afterglow" of a  
pulsed discharge. One of  the unique modifications was to subject the  
plasma to a static magnetic  field so that the electrons were in  
cyclotron resonance with either  wave. All sorts of nonlinear  
phenomena from harmonic generation to  modification of rate processes  
could be observed with relatively small  microwave power (Å 200 mW or  
less).



 From <http://ion.le.ac.uk/heating/history_of_rf_heating.html>:

The Luxembourg effect

In the early 1930s a high power radio broadcasting station was built  
in Luxembourg. Tellegen (1933) reported that the modulation of the  
Luxembourg station could be heard in the background of a programme  
transmitted from Beromunster and received at Eindhoven. Soon after,  
Bailey and Martyn (1934) suggested that the effect was caused by the  
powerful Luxembourg transmitter modifying the radio propagation  
characteristics of the ionosphere. When the Beromunster signal passed  
through this region its propagation was affected by the modified  
ionospheric conditions, and in this way amplitude modulation from the  
Luxembourg signal was transferred to the Beromunster signal.

  The ionosphere as a plasma laboratory

The Luxembourg effect became known as cross-modulation, and  
scientists began to explore the possibilities of utilising high power  
radio waves in controlled ionospheric experiments. This was the  
beginning of employing modification of the ionosphere to complement  
plasma experiments in the laboratory. Bailey and Goldstein were among  
the first to suggest this, when in 1958 they suggested the use of  
radio waves near the electron gyrofrequency to control electron  
temperatures. Many other experiments were suggested, for example,  
Ginzburg and Gurevich (1960) suggested modification of the F-region  
ionosphere.


-- 
Steve Byan <stevebyan at mac.com>
Littleton, MA 01460

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