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RadioRadio WavesRadio EquipmentDirection FinderMeasuring InstrumentsHigh FrequencyField StrengthCharacter RecognitionRadio ReceiversPiezoelectric CrystalsWireless TelegraphRadiation Resistancein DesignMicrowaveWave PropagationTuned CircuitSurveillance RadarTelevisionGround Wave PropagationReactance Transformer