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I was curious about something regarding radio waves. When we're talking about differences of 200 MHz between waves, is there any way of any noticeable interference occurring? By noticeable I mean noticeable in a practical sense. I want to know if mobile phones can interfere with control towers when on a plane, from my research till now the frequencies can't get any closer than 200 MHz

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    $\begingroup$ Mobile phones use an ultra-wideband transmission scheme which had different implication for "interference" than you might expect if you are thinking in terms of constructive/destructive interference of coherent signals. $\endgroup$ – dmckee --- ex-moderator kitten Dec 12 '19 at 18:12
  • $\begingroup$ @dmckee what do you mean by "ultra-wideband transmission scheme"? $\endgroup$ – hyportnex Dec 12 '19 at 19:19
  • $\begingroup$ @hyportnexit would appear that I have confused my terminology. That should read "spread-spectrum" though the point that the technology creates and responds to interference differently than coherent transmission remains. $\endgroup$ – dmckee --- ex-moderator kitten Dec 12 '19 at 23:40
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Whether 200MHz frequency difference between two signals matters or not depends on the power ratio of the signals in the "victim" receiver and the method of the detection in it.

High level interference in a receiver can cause all kinds surprising problems related to the nonlinearities in the receiver chain, primarily generated in the front-end amplifier and mixer but also further down the chain. These non-linearities can create a plethora of inter-modulation and cross-modulation products, etc., various spurious signals, "spurs" and "intermods" are the buzzwords, that are very difficult to control and filter. Some signals are more sensitive to these inter-modulation products than others, broadly speaking the wider the spectral bandwidth relative to that of the intermods the easier is their removal, but again there are no general rules.

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