Eli5: How, poisition of unknown radio receiver tracked, operating in a spefic frequency.
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Modern radio tunes in a frequency using local oscillator, and uses multipliers and mixers to obtain an intermediate frequency, which is lower than the tuned in frequency. That intermediate frequency is quite easy to listen to but it does not carry very far, tens of meters at best. With triangulation and highly directional antennas you can pinpoint a house among many houses where that listener is.
In short, every “listening” radio is emitting radio frequencies too.
Nowadays, digital radios emit alot of garbage which are listenable too. With a radio scanner you can listen almost everything, not what a radio is hearing, but is radio on or off.
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