Unit 8: Transmission Systems and Frequency Spectrum

Question 1

What is Telecommunications?

Answer 1

It is the transmission of information over a communications line and the transmission of signals over a distance for the purpose of communication

Question 2

What is a wave and its components?

Answer 2

It is a periodic oscillation or electromagnetic phenomenon.

1. Period (t)
2. Frequency (f)
3. Amplitude (A)

Question 3

What is a signal?

Answer 3

It is a time-varying electrical quantity such as voltage or current by which messages or information/data can be transmitted

Question 4

What is the difference between an analog signal and a digital signal?

Answer 4

Analog is continuous in nature

Digital is discrete and quantized

Question 5

What is modulation?

Answer 5

It is the process of manipulating some characteristic of a since wave, also known as superimposing the information/message signal onto a carrier wave

Question 6

Modem

Answer 6

Short for modulator-demodulator, is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information

Question 7

Multiplexing

Answer 7

aka muxing, is the process where multiple analog message signals or digital data streams are combined into one signal over a shared medium

Question 8

Multiplexing Access Types

Answer 8

1. Frequency Division Multiple Access (FDMA) - different pitches
2. Time Division Multiple Access (TDMA) - different times
3. Code Division Multiple Access (CDMA) - different languages

Question 9

Crosstalk

Answer 9

Any disturbance caused by the electric or magnetic fields

Question 10

Attenuation

Answer 10

Weakening of a signal as it is transmitted

Question 11

Scattering

Answer 11

Occurs when a wave encounters discontinuities in the transmission medium

Question 12

Dispersion

Answer 12

Seen in digital transmissions and light pulses

Question 13

Distortion

Answer 13

The difference between the expected output signal and the actual output signal

Question 14

Transients

Answer 14

Brief voltage or current spikes

Question 15

Echoes

Answer 15

Reflections of a portion of the signal wave caused by inconsistencies along the transmission path

Question 16

What is the difference between Bandwidth and Throughput?

Answer 16

Bandwidth - size of the pipe

Throughput - how fast data goes through the pipe

Question 17

Radio Act of 1912

Answer 17

Required registration of transmitters with the Department of Commerce

Question 18

Communications Act of 1934

Answer 18

Federal Communications Commission (FCC) - Non-federal users (civilians)
National Telecommunications and Information Administration (NTIA) - Federal users

Question 19

International Telecommunications Union (ITU)

Answer 19

Organization established to standardize and regulate international radio and telecommunications

Question 20

DoD Area Frequency Coordinators (AFC)

Answer 20

Responsible for ensuring successful frequency coordination in the geographical areas

Question 21

Air Force Frequency Management Agency (AFFMA)

Answer 21

Defends and articulates AF spectrum access to regulatory agencies

Question 22

MAJCOM Frequency Managers

Answer 22

Carry out AF policy, practices, and procedures for managing use of the RF spectrum

Question 23

What are the 3 primary reasons to be responsible for frequency management for a Communications and Information (C & I) officer?

Answer 23

1. Equitable RF distribution
2. Reduction of RF interference
3. Personnel safety