means Radio Detection and Ranging.
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.
a pulse is transmitted then this is a TX Pulse and when its
recieved then this is a RX Pulse.
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.
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.
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).
Antenna also receives RX Pulses (echoes from targets) this RX
Pulse is put to the Receiver.
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.
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.
Transmitter has a switch that switches from TX (Transmitting)
to RX (receiving)
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 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
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
Pulse Modulator delivers power to the transmitter, it has to make
the power continious regarding the voltage, power, duration and
timing to the transmitter.
power & voltage to the transmitter should never vary during
stand in front of a Radars antenna, the radiation emitted from
it can cause sterilization or even cancer.
sure you know what set up you have on your vessels radars
head up, stabilized
the following too;
Know what scales your radars are set up on
Make sure you know about sea and rain clutter and how to get rid
Know how to set up a radar
Range hopping, know how to retune your radar once you've moved
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.
stands for Electronic bearing line.
stands for a variable range marker.
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.
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)
You'll be asked how to check that the radar is working at its
by using the
Performance Monitor button (On a radar consol its called "Perf
He'll ask you how to check the performance of the radar
the PERF MON button on the consol
it to the 24 miles scale
and Hold the T.R. Monitor (This tests the transmission performance)
the "Data Wheel" to obtain 4 or Maximum arcs on screen
the PERF MON Button
the PERF MON Button again this will now check the T.X. Monitor
(This checks the receiving performance)