A null detected by listening for the minimum or the absence of an audible signal

Related Terms

HARMONIC

1. A sinusoidal quantity having a frequency that is an integral multiple of the frequency of a periodic quantity to which it is related. 2. A signal having a frequency which is an integral multiple of the fundamental frequency.

HOP

Travel of a radio wave to the ionosphere and back to earth. The number of hops a radio signal has experienced is usually designated by the expression one-hop, two-hop, multihop, etc

HEAT LIGHTNING

A flash of light from an electric discharge, without thunder, believed to be the reflection by haze or clouds of a distant lash of lightning, too far away for the thunder to be audible

HOMING

Navigation toward a point by following a signal from that point. Radiobeacons are commonly used for homing.

INFRASONIC

Having a frequency below the audible range. Frequencies above the audible range are called ULTRASONIC.

INTERNATIONAL CALL SIGN

An alpha-numeric symbol assigned in accordance with the provisions of the International Telecommunications Union to identify a radio station. The nationality or the radio station is identified by the first three characters; also referred to as call letters or signal letters.

BEAT TO QUARTERS

Prepare for battle (beat = beat the drum to signal the need for battle preparation)

INTERROGATING SIGNAL

The signal emitted by interrogator to trigger a transponder

INOPERATIVE

Said of a sound signal or radionavigation aid out of service due to a malfunction

FLAG HOIST

A number of signal flags strung together to convey a message.

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