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Radar means Radio Detection and Ranging.

Radar works by putting out microwave radiation pulses and when it hits a target (ship, land etc) it returns to the Radar, the Radar then measures the time, frequency, strength of the pulse and the direction.

When a pulse is transmitted then this is a TX Pulse and when its recieved then this is a RX Pulse.

It is an electromagnetic system that uses RADIO WAVES which travel at the speed of light which is approximately 300,000 kilometers (186,000 miles) per second.

A Pulse is sent out at the speed of light which is 300,000,000 m/s and once it hits a target, the pulse is sent back as an echo, the antenna then picks up the pulse (RX) and delivers it to the receiver as an electronic signal, the signal gets amplified and displayed on the radar screen.


The antenna rotates slowly to pick up any targets in your area, it sweeps a 360 degree angle putting out a narrow beam of TX Pulses from the Transmitter (1 degree = 1 Pulse).

The Antenna also receives RX Pulses (echoes from targets) this RX Pulse is put to the Receiver.


The Transmitter puts out a very large burst of energy (a pulse) which last for 0.1 - 5 microseconds and then does nothing until the next pulse is ready to send.

The Transmitter has to send short pulses because it has to be able to receive pulses too, so in reality its listening for pulses more than it is transmitting pulses.

The Transmitter has a switch that switches from TX (Transmitting) to RX (receiving)


The antenna recieves an echo and this echo is converted to a frequency of around 30 MHz and then amplified at this frequency and then sent to the computer inside the radar, the computer now converts the analogue signals to digital signals using an analogue to digital convertor and decifiers the information about the target.

Radar Display Unit

The Radar Display Unit is simply a cathode ray tube (CRT), the information from the computer is placed onto the screen by a a sweeping motion going clockwise, when a echo is placed onto the screen a bright spot appears showing you the course and distance from your vessel

(Caution) watch incase your picking up false echoes, rain and sea gain set incorrectly wll cause false echoes to appear on the screen as will a large vessel or high cliffs)
A sailing vessel is a very bad target as most of the vessel is low in the water, recommended to place a radar reflector on every vessel.

Pulse Modulator

The Pulse Modulator delivers power to the transmitter, it has to make the power continious regarding the voltage, power, duration and timing to the transmitter.

The power & voltage to the transmitter should never vary during a pulse.


Never stand in front of a Radars antenna, the radiation emitted from it can cause sterilization or even cancer.

Oral Exam Tips

Make sure you know what set up you have on your vessels radars

Ships head up, stabilized

North up, stabilized

Know the following too;

(1) Know what scales your radars are set up on

(2) Make sure you know about sea and rain clutter and how to get rid of it

(3) Know how to set up a radar

(4) Range hopping, know how to retune your radar once you've moved the scale

(5) When coming close to land or any target, switch the scale down and re-tune the radar, keep dropping the scale and you'll see the mouth of the harbour opening up.

E.B.L. stands for Electronic bearing line.

V.R.M. stands for a variable range marker.

A large target will affect how good a target is picked up on your radar screen, a very high cliff will give you a good picture on your radar screen, one of the worst targets is a sailing vessel without a radar reflector or a low gradient beach.

During a radar exam you will be asked to set up a radar, screw all the knobs to zero, and switch on the radar, wait till the allotted time has expired and switch the radar on, now turn up the gain so you can see a green/blue screen, tune in till you get the maximum boxes for the strength of the pulses, adjust the rain and sea clutter switches (Important,,,,,, adjust the sea/rain clutter knobs even it its a beautiful day, the examiner will send you out with this if you don't do it)


(Q) You'll be asked how to check that the radar is working at its Best
(a) by using the Performance Monitor button (On a radar consol its called "Perf Mon")

(Q) He'll ask you how to check the performance of the radar

Push the PERF MON button on the consol

Switch it to the 24 miles scale

Press and Hold the T.R. Monitor (This tests the transmission performance)

Use the "Data Wheel" to obtain 4 or Maximum arcs on screen

Release the PERF MON Button

Press the PERF MON Button again this will now check the T.X. Monitor (This checks the receiving performance)

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