An apparatus for detecting the presence of ice includes a sensor including a radio-frequency transmission line providing a characteristic impedance, a source coupled to the transmission line and operable to inject a wave into the transmission line, a summer operable to create standing wave, the standing wave including the sum of the injected wave and a reflected wave reflected by the end of the transmission line, the summer being connected between the source and the transmission line, and a detector for detecting the voltage of the standing wave. An embodiment may further include a comparator operable to compare the detected voltage with reference data for determining the presence of ice contacting the sensor.