Radar

Question 1

RADAR stands for ___

Answer 1

Radio Direction and Ranging

Question 2

It works on the basis that ___ ___ can be reflected off suitable objects, and the time between transmission and reflection can be used to calculate the distance because the speed of transmission is known

Answer 2

microwave pulses

Question 3

RADAR uses _HF

Answer 3

SHF

Question 4

RADAR is limited to ___

Answer 4

line of sight

Question 5

RADAR is best with __ wavelengths

Answer 5

short

Question 6

A pulse is a short burst of __ energy mixed with long periods of silence

Answer 6

EM

Question 7

Contiuous wave radar is used in radio __ and __ systems

Answer 7

altimeters, Doppler

Question 8

RF energy is created with ____

Answer 8

magnetrons

Question 9

The RF energy is released at intervals, known as the ___, which are determined by the range required.

Answer 9

PRF

Question 10

The range of a target is determined by measuring the ___

Answer 10

time taken for a pulse of energy to travel there and back.

Question 11

It takes _ microseconds for a wave to travel 1000m

Answer 11

3

Question 12

Primary radar has a time interval of _ microseconds for every 1000m slant range

Answer 12

6

Question 13

___ wavelengths are required to penetrate cloud

Answer 13

long

Question 14

The strength of an echo received back at a radar set varies with the ___ of the target and its ___.

Answer 14

size, distance

Question 15

The returning pulse is not reflected, but ___, as the pulse makes valence electrons ripple and release energy

Answer 15

re radiated

Question 16

Power is ___ proportional to the square of the field strength

Answer 16

directly

Question 17

Echo power is ___ proportional to the distance of the target

Answer 17

inversely

Question 18

Every time you double the range of a target, you reduce the power of its echo by 2^_

Answer 18

4

Question 19

To double the effective range of the primary radar, the power output must be increased by a factor of __

Answer 19

16

Question 20

The transmitter has to generate __ power at ___ frequencies

Answer 20

high high

Question 21

The radio frequency energy is produced inside the __ __ by a ___

Answer 21

HF oscillator, magnetron

Question 22

The transmitter has to be capable of switching on and off rapidly to produce ___, achieved by the ___

Answer 22

pulses, modulator

Question 23

The transmitter has to send out pulses at regular intervals, via the ___

Answer 23

synchroniser

Question 24

The pulses travel through a ___ cable, or hollow metal tube called a ___ ___, which prevents excessive power loss at it is tuned to the wavelength.

Answer 24

coaxial, wave guide

Question 25

The RF energy is injected into the waveguide by a ___

Answer 25

probe

Question 26

A waveguide is not required for weather radar, as it uses ___ on a flat array

Answer 26

slots

Question 27

The transmitted signal is very ___, but the received one is very weak.

Answer 27

strong

Question 28

The receiver circuits must be protected against the ___ energy from the transmitted signals.

Answer 28

high

Question 29

A duplexer is a routing device that directs outgoing pulses to the ___ and incoming pulses from the ___ to the ___.

Answer 29

antenna, antenna, receiver

Question 30

Orange peel dishes produce a ___ and __ beam

Answer 30

wide narrow

Question 31

Parabolic dishes produce a __ beam, spreading more distance

Answer 31

focussed

Question 32

A phase array has a series of ___ ____, like small dipoles, which are arranged in a line and fed with signals that are in phase with each other.

Answer 32

conducting elements

Question 33

The interference pattern from a phase array produce a __ beam

Answer 33

pencil

Question 34

When receiving, a larger dish can receiver ___ signals

Answer 34

weaker

Question 35

Beam width (degrees) = ___

Answer 35

( 2 x wavelength in cm ) / diameter (ft)

Question 36

Beam width (degrees) = ___

Answer 36

( 70 x wavelength ) / diameter

Question 37

The advantages of a narrow beam are ___

Answer 37

• Bearings easier to acquire
• Greater concentration of energy
• More range
• Target definition

Question 38

A ___ pulse length with a ___ beam will get the best picture

Answer 38

short, narrow

Question 39

The antenna should be able to produce a ___ beam and receive a __ beam

Answer 39

thin wide

Question 40

___ antenna can eliminate lateral lobes, and concentrate more energy in the main beam

Answer 40

slotted

Question 41

The receiver should have a _ overall gain, with ___ random noise in the circuitry

Answer 41

high little

Question 42

The received signal is sent to the ___ ___ ___

Answer 42

plan position indicator