Advanced signals

Question 1

Define electricity.

Answer 1

Electricity is the ordered movement of the free electron

Question 2

List the effects of current

Answer 2

-heating effect
-magnetic effect
-chemical effect

Question 3

Define voltage

Answer 3

Voltage is the force or pressure at the source of electro motive force (EMF)

Question 4

List the methods of producing voltage

Answer 4

1. Chemical
2. Mechanical
3. Friction

Question 5

List the requirements of a simple circuit

Answer 5

-power source
- a conducting path
- load(resistor)
- control/switch

Question 6

Define modulation

Answer 6

Process by which audio frequencies are super imposed onto the RF carrier wave.

Question 7

State what is meant by double sideband

Answer 7

Frequencies are created both above and below the carrier known as side bands.

Question 8

List the 3 types of modulation

Answer 8

1. Analogue
2. Digital
3. Spread spectrum (frequency hop and direct sequence)

Question 9

Define bandwidth

Answer 9

Bandwidth is the width of a band of frequencies covering a particular signal.

Question 10

Characteristics of radio waves?

Answer 10

Velocity
Frequency
Wave length

Question 11

List the main types of antenna

Answer 11

Resonant antenna
Broadband antenna
Travelling wave

Question 12

One broadband antenna ?

Answer 12

VHF man pack whip
VHF vehicle whip
150w HF broadband antenna

Question 13

One resonant antenna?

Answer 13

1/2 dipole
1/4 monopole
1/4 and 3/4 end fed

Question 14

List 4 properties of an antenna

Answer 14

Polarisation
Polar diagram
Antenna gain
Matching
Antenna efficiency
Antenna dimensions

Question 15

Define antenna gain

Answer 15

An antenna has gain if it radiates more power than another antenna, this power is radiated one way making it directional.

Question 16

Define polarisation

Answer 16

An antenna is either horizontal or vertically polarised, some antennas radiate more power in particular directions.