If there are lots of different radio signals with the same or very similar wavelengths, how is it possible for a radio to pick up just one signal?
In: Technology
In general, it can’t.
If two signals over lap, both will be received and will, generally, garble the message. While frequency – the number of oscillations of the carrier signal – is important, bandwidth – the “width” of the information in hertz – is important, too.
For example, a radio station on 101.3 FM actually extends from 101.2 to 101.4. This spacing prevents signals from “clipping” into one another when adjacent channels are co-located. 101.1 doesn’t go past 101.2.
With two stations at the same frequency, they’re usually spaced far enough apart that the power of one broadcast is significantly weak within the area of reception of the other station, thus interference is avoided.
Propagation phenomena changes with different frequencies, though. AM broadcasts can travel farther at night, and some stations are required to reduce power at these times to reduce interference.
Additionally, it’s possible to encode transmissions to be dug out later. This is not uncommon in things like radars, where a code is embedded in the phase of the transmission and returns can be discriminated from interference despite being at the same frequency.
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