Ask Dr. SETI ®
As you may or may not be aware, the military ( and increasingly the business community ) are using Spread Spectrum type modulation to transmit voice, data, etc. The point being that the intelligence in the signal is spread widely over a broad range of frequencies rather than concentrated on one frequency ( Amplitude Modulation ) or a very narrow band of frequencies ( Frequency Modulation.) Therefore, you can be listening on one or even several frequencies and still not comprehend an intelligible signal. Also, this technique allows signal detection well below the noise threshhold. Indeed, I am given to understand that with frequency-hopping techniques it is well nigh impossible to detect or at least demodulate the intelligence from the signal. You probably are well aware of all this, but as an amateur organization it is always possible that with time and money pressures an area of signal detection is not yet utilized.
Wishing you the best,
The Doctor Responds:
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this page last updated 28 December 2002
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