Interference is one of the most complex types of noise affecting communication range. It occurs when both a direct signal and a reflected signal (from some obstacle) with an already shifted phase arrive at the receiving point. If, in addition, the receiving antenna picks up harmonics (frequency-shifted signals) of the main transmitter, plus nearby frequency signals and harmonics from other transmitters (both direct and reflected), and on top of that all the electromagnetic “noise” generated by modern civilization… it becomes evident that interference is practically impossible to analyze and predict. Fighting an invisible enemy is always more difficult than open battle.
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