How does this circuit detect the geomagnetic signals

[shabby]

how does this circuit detect the geomagnetic signals??? wats the mechanism????

http://www.electronics-lab.com/projects/science/002/index.html

kindly help...!!!

 

[Resqueline]

That circuit is an RF-oscillator/ transmitter. What the text implies but doesn't say is that you need a working AM-radio and a station to listen to too.
When two transmitters are real close in frequency you can hear the difference as a tone in the speaker.
Now, ferrite as is used in one of the frequency-determining components in this transmitter, has a magnetic permeability μ that is obviously a major inductance determining factor. The thing with ferrite is that μ is not constant, but goes down with increased magenetic fields.
Thus when the ferrite rod is aligned with earths magnetic field the inductance is lowered and the frequency gets higher, altering the interference tone in the radio.
Have a look here if you'd like to learn more about electromagnetism.

 

[andreapg]

I' m not knowledgeable in this area, but I presume this circuit may be utilized to get earthquake forecasts.
How I said I am not knowledgeable, but this circuit seems like too simple to be an earthquake precursors detector...
Visit this page:
http://www.vlf.it/dionysios/dionysios.html

 

[Resqueline]

Interesting link andrea.
Yes, I believe shabby's circuit was not meant to be used as a magnetometer. It would be far too temperature sensitive etc. and I believe it was just meant as a scientific experiment to show the properties of ferrite and a novel way of using it to detect magnetism, but I can see why you made the connection.

 

[andreapg]

I think that there may be different ways to detect earthquake precursors. For example, in my country (and in other countries) some radio amateurs are making experiments.
But unfortunately italian official "scientists" (INGV) do not belive in earthquake precursors, I don' t know the reason.
Do they think to be more knowledgeable than other scientist?
Are there any commercial interests?
I'm not a scientist, but I know that some days before L' Aquila earthquake (06 April) someone said something about radon signals...

 

[Resqueline]

Scientists are both sceptic & proud I think. If they didn't think of it then certainly no-one else should be capable.. I guess any official organ also would be in a state of denial, until proven otherwise. Bureaucrats are not known for their ability to think & adjust, but rather their ability to cover their backs & positions.
I don't think there are any commercial interests. They would have done their research & been on the market a long time ago.
To me it seems only natural that there could be signals like electromagnetism & gases emanating from the (stressed) ground before a quake, and that the timing could be sun & moon related.

 

[shabby]

wats an rf oscillator?? how does this small circuit actually detect earth's geoagnetic field.?? wats the probe to detect signals?? how is the received signal processed???

 

[Resqueline]

I thought I had explained all that in the first post..
RF = Radio Frequency; that small circuit is a radio transmitter, depending on the 60pF variable capacitor and the ferrite cored coil to determine its frequency.
The earths magnetic field is attracted to and collected/intensified by the ferrite rod when it aligns axially with the field. The magnet polarizes the rod to make it possible to discern north from south. So when the rod points north there is a stronger permanent magnetic field in it than when it points south. A (slightly) stronger field makes the inductance drop (slightly) and thereby the transmitted frequency rises.
The probe is the ferrite rod (+ the magnet).
The signal is received and "processed" by the nearby AM radio being tuned to a radio station. The difference in the radio stations frequency and the circuits frequency is heard as a (varying) whistle in the speaker. This process is called mixing or interference, and results in a beat frequency (note).