Return to KLUBNL.PL main page

rsgb_lf_group
[Top] [All Lists]

Re: LF: Schumann

To: [email protected]
Subject: Re: LF: Schumann
From: Marco IK1ODO -2 <[email protected]>
Date: Thu, 02 Jun 2011 16:22:39 +0200
In-reply-to: <[email protected]>
References: <[email protected]> <[email protected]> <[email protected]>
Reply-to: [email protected]
Sender: [email protected]

The first Schumann resonance is not at (300000/40000)=7.5 Hz, but higher, usually around 7.7-7.8 Hz. I was astounded when I observed it for the first time about 12 years ago and found that the frequency was "not right" !:-) The reason is simple: our Earth is quite transparent at very low frequencies, so the average circumference of the ionosphere-Earth waveguide is shorter than 40000 km. In other words, the center of the first Schumann resonance is below your feet, at a deptht of approximately 300 km. The second one is a little bit higher than 15 Hz, and progressively the other come closer to harmonics of a 40000 km wavelenght; but since the Q is low, it is dfficult to extimate the exact frequency.
Have a look at http://www.vlf.it/Schumann/schumann.htm.
Years ago there was a website from Stanford University reporting the measured frequency of Schumann resonances vs. time. The frequency changes because of day/night ionospheric height variations, and beacuse of SIDs and other disturbances. Fascinating ! To receive them you need a very large coil, or a simple E field receiver and a quiet location; feed the signal to an audio interface, and run a spectrogram in average mode. Quite easy to say, but it takes some ingenuity and work to extract an useable signal. Renato IK1QFK has a live spectrogram covering from 0.1 Hz up, see http://www.vlf.it/cumiana/livedata.html - today we have thunderstorms in the area, and the signal is completely wiped out.

Vy 73 - Marco IK1ODO



<Prev in Thread] Current Thread [Next in Thread>