Navigation and Seamanship

6.6.3. Radio gonio-meter(Loop Antenna)

The goniometer (Gonio’ means angle and ‘meter’ means measurer) measures the angle between the ship’s fore-aft centre line and the radio transmitter from where the signals are received . It helps in obtaining the bearing of the radio transmitter relative to the ship’s head. Goniometer consists of two fixed coils(also called field coils) placed at right angles to one another. The loops are connected through cables to their respective coils. The search coil is connected to the receiver input. The goniometer aerial placed in the path of a radio wave will be cut by the alternating field and an EMF will be induced in it.

If the plane of this antenna pointed to a radio beacon, the signal strength will be the maximum, while a signal facing the loop induced voltages that canceled each other out, resulting in a weak or null signal. The loop antenna was connected to an amplifier which will amplify the weak signal in to several thousand times .

Range of Transmission

Range of transmission is the distance in nautical miles at which the radio signal is received by the vessel. In some cases the transmission power is reduced guring night hours and this will be mentioned in the list.