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April 17[edit]

How do they make sure radio waves won't overlap each other?[edit]

We watch Televising by grabbing radio waves that carry a video signal representing moving images, along with a synchronized audio channel. How do they make sure this radio waves won't overlap each other? Rizosome (talk) 17:14, 17 April 2021 (UTC)[reply]

Three answers, depending on what you mean by "overlap";

If you are in a room with two light bulbs, how do you make sure the light waves won't overlap each other?
Different TV and radio stations are on different frequencies, and (in the US) the FCC makes sure that they don't interfere with each others signals on a particular frequency.
See Television transmitter#Combining aural and visual signals for analog TV. With digital TV it's all bits and the computer in the TV figures out which bits are which.

--Guy Macon (talk) 17:26, 17 April 2021 (UTC)[reply]

Its actually incredibly complex, there is so much engineering going on behind the scenes it's unreal. See radio resource management and the plethora of techniques listed that are used to prevent co-channel interference. Jules (Mrjulesd) 17:49, 17 April 2021 (UTC)[reply]

This specific case showing how politics can come into it may be of interest. --184.147.181.129 (talk) 06:44, 18 April 2021 (UTC)[reply]

Regarding radio, if you've ever had your car radio on when you were close to a broadcasting antenna, you might observe that it overwhelms every channel on your dial. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:24, 18 April 2021 (UTC)[reply]

That's because the signal is strong enough to bypass the antenna circuit and begin to drive the speaker circuit directly. The purpose of the antenna circuit is to amplify a specific signal and send that amplified signal to your speakers. If the signal in the air is already stronger than the amplified signal from the antenna circuit, then it will be broadcast instead of your antenna signal. This is more pronounced with AM radio than with FM radio; indeed, with AM radio, you can build a simple receiver without a battery; if you're close to the transmitter it will broadcast the signal without any external power source at all; the RF signal is sufficient to drive a small speaker itself. This page describes building simple radio receivers that don't require any power source. --Jayron 32 14:05, 19 April 2021 (UTC)[reply]

For radio waves in vacuum, or air, or on the surface of metal, or in common insulators, the response is linear so that the superposition principle applies. This means that the waves can be separated out again and can pass through each other without affecting each other. Some materials are non-linear. (see Nonlinear optics) These include semiconductors with junctions or some kinds of crystals. In these the waves can mix to make difference and sum outputs, and also harmonics. But the TV will make sure that these are only used by design and not by mistake. Baseball Bugs' example will be due to a non-linearity in the first stage of the receiver that is loaded beyond its design limit. Graeme Bartlett (talk) 12:47, 19 April 2021 (UTC)[reply]

Another answer: Radio antennae use something called a LC circuit, or inductor-capacitor circuits. Both electronic components have a certain frequency, and when they are the same, the LC circuit enters a 'resonance' state, where the inductor and capacitor are synchronized. This leads to them receiving only a certain frequency of wave (see LC circuit#Applications). This can tune the receiver to whatever frequency you want. I don't know if that's what you're asking, but there's my two cents. Sungodtemple a tcg fan!!1 !11 !! (talk) 14:07, 20 April 2021 (UTC)[reply]