14. radar part 1
Radar range accuracy should be within......
1.5 % of the range scale in use.
Radar bearing discrimination should be within.....
2.5 degrees
A typical figure for minimum radar range is......
25 metres.
Radar range discrimination should not be less than......
50 metres.
A typical pulse repetition frequency is......
500 to 3000 pulses per second.
A radar with a wavelength of 3.2 cm would have a frequency of about....
9,375 MHz
S-band radar has a wavelength of ....
9.2 to 10 cm
A target with a smooth surface will only give a good echo if it's aspect relative to the direction of the radar beam is......
90 degrees.
An alternative name for the anti-rain clutter control is the....
F.T.C. control
Radar bearing discrimination depends mainly on which of the following?
Horizontal beamwidth
Which of the following has the most effect on the definition of a small target on the radar display?
Horizontal beamwidth
Weaker echoes are converted to signals of detectable strength by the....
I.F. amplifier
Range discrimination depends mainly on which of the following?
Pulse length
Which of the following has most effect on the size and shape of small radar targets?
Pulse length
An alternative name for the anti-sea clutter control is the....
S.T.C. control
A complete oscillation of a radio wave is called......
a cycle.
Side echoes appear on the radar display as.....
a symmetrical arc of echoes.
Compared to the visual horizon, the radar horizon is....
about 6% further away
Radar range accuracy depends mainly on the......
accuracy of the timebase.
Target echoes are received in the display unit in the form of....
an increased potential to the grid
Indirect echoes can be recognised by the fact that they....
appear in shadow sectors
Multiple echoes can be recognised because they
at constant range intervals
When side echoes are displayed, the true target echo will appear.....
at the centre of the pattern.
The purpose of the anodes in the C.R.T. is to....
attract the electrons to the screen
The symbol shown here identifies the....
bearing cursor
A function of the deflection coils in a C.R.T. is to....
cause the electrons to form the trace
Marine radar wavelengths are measured in
centimetres.
The principle of a corner reflector is that it.....
changes the direction of the beam by 180 degrees.
The function of the waveguide is to....
conduct pulses to and from the scanner
A radar target is likely to give the poorest reflection if it's shape is......
conical.
As distance from the scanner increases, the power of the radar beam....
decreases rapidly
If your radar suffers from shadow sectors you should....
determine and record their limits
Echoes from rain can be reduced using the....
differentiator control
In addition to initiating the action of the transmitter, the trigger unit also sends a pulse to the:
display to start the timebase.
Multiple radar echoes are caused by....
eflection between own ship and a large close target
The electrons in the Cathode Ray Tube ( CRT) are attracted....
from the cathode to the anodes
On a radar display, this symbol identifies the....
gain control
A target with a "rough" surface is likely to......
give a good echo at any aspect.
Radar targets give the strongest echoes if they are.....
hard and dense.
This display symbol shown is for....
head-up presentation
The symbol shown here identifies the....
heading marker alignment control
Bearing accuracy depends mainly on....
horizontal beamwidth
The commonest type of radar scanner is the....
horizontal slotted waveguide
The trace on the display rotates....
in synchronization with the scanner
A corner reflector is used to......
increase the detectability of small targets.
Super-refraction is likely to cause....
increased target detection ranges
Signals are converted to a suitable form for the display by the....
local oscillator
The main component of the transmitter is the....
magnetron
The transmitted frequency is determined by the design of the....
magnetron
The purpose of the bearing cursor is to....
measure the bearing of targets
If the trace is not correctly centred, error may occur when....
measuring bearings
A radar target of a certain size is likely to give a stronger echo if it is made of.....
metal.
One cause of bearing error is....
misalignment of the centre of the trace on the display
Incoming target echoes are detected by the....
mixer crystal
The intermediate frequency is generated by the....
mixer crystal
The transmitted pulse length is determined by the action of the....
modulator
To provide accurate target bearings the radar beam must be......
narrow in the horizontal plane.
Indirect echoes are caused by reflections from.....
obstructions close to the scanner.
The cause of shadow or blind sectors is....
obstructions on your own ship
Multiple echoes appear on the screen....
on the correct bearing at double the true range
Indirect echoes appear on the display....
on the true range, but on a false bearing
The horizontal pattern of a radar beam consists of......
one large lobe and smaller side lobes either side
The most common cause of radar interference is....
other radar transmissions on a similar frequency
Maximum radar range depends partly on the....
peak power output.
Radar does not transmit continuously because it would......
prevent detection of targets.
The purpose of the T/R cell is to....
protect the receiver during transmission
The function of the local oscillator is to....
provide a frequency for mixing with the target signals
Altering the range scale may automatically change the....
pulse length
Minimum radar range depends mainly on.....
pulse length.
This symbol identifies the....
range scale control
A factor in determining a radar maximum range is......
receiver sensitivity.
The effect of the anti-rain clutter control is to....
reduce the size of all echoes
The vertical beam must be wide enough to allow for the......
rolling and pitching of the ship.
The display trace is caused to rotate in synchronisation with the scanner by a signal from the....
scanner motor
The magnetron sends the R.F. pulses to the....
scanner unit
The unit which sends returning target echoes to the receiver is the....
scanner unit
Horizontal beamwidth depends mainly on....
scanner width
Accurate target bearings are obtained by......
synchronizing the radar beam and the trace.
The purpose of the gain control is to adjust....
the amplification of the target echoes
Half the vertical distance between the crest and the trough of a radio wave is called.....
the amplitude
The brilliance control of a Cathode Ray Tube ( CRT ) operates on....
the anode
Vertical beamwidth is determined by....
the design of the scanner
The distance of the radar horizon is largely determined by......
the downward refraction of radar waves.
The tuning control adjusts....
the frequency of the local oscillator
The display symbol shown here is for....
the power monitor
Target ranges are obtained from......
the range marker.
Side echoes are caused by reflections from....
the side lobes of the radar beam.
Before taking target bearings, you should check that....
the trace is correctly centered
The brilliance control should be adjusted so that
the trace is just barely visible
The horizontal distance between the adjacent crests of a radio wave is called....
the wavelength
The gain control should be adjusted so that
there is a light speckled background on the screen
Target echoes appear along a line called the......
timebase.
The transmitter P.R.F. is determined by the....
trigger unit
Radar bearing discrimination is the ability to display separately....
two targets at same range on slightly different bearings
On a radar display, this symbol indicates the....
variable range marker
The distance of a target can be measured by using
variable range marker
The intensity of the electron beam in the C.R.T. is controlled by....
varying the potential on the grid
Signals are converted to a suitable form for the display by the....
video amplifier
The tuning control is best adjusted by using the
visual tuning indicator
Super-refraction is normally caused by....
warm air over a cool sea surface
