Physics > Communication Systems > 1.0 Elements of a communication system
Communication Systems
1.0 Elements of a communication system
1.1 Terminology used in electronic communication system
1.2 Bandwidth of signals
1.3 Bandwidth of transmission medium
1.4 Earth's atmosphere
2.0 Radio waves
3.0 Modulation
1.3 Bandwidth of transmission medium
1.2 Bandwidth of signals
1.3 Bandwidth of transmission medium
1.4 Earth's atmosphere
The commonly used transmission media are wire, free space and optical fibre cable.
Coaxial cable is a widely used wire medium. It offers a bandwidth of approximately 750 $MHz$. These cables are normally operated below 18 $GHz$.
Communication through free space using radio waves takes place over a very wide range of frequencies ranging from a few hundreds of $kHz$ to a few $GHz$.
Optical fibre communication is used in the frequency range of 1 $THz$ to 1000 $THz$ (microwaves to ultraviolet). An optical fibre can offer a transmission bandwidth in excess of 100 $GHz$.
Some important wireless communication frequency bands is as shown in the table.
| S. No. | Service | Frequency | Comments |
| 1 | Standard AM broadcast | 540 - 1600 $kHz$ | |
| 2 | FM broadcast | 88 - 108 $MHz$ | |
| 3 | Television | 54 - 72 $MHz$ 76 - 88 $MHz$ 174 - 216 $MHz$ 420 - 890 $MHz$ | VHF (very high frequencies) TV UHF (ultra high frequencies) TV |
| 4 | Cellular Mobile Radio | 896 - 901 $MHz$ 840 - 935 $MHz$ | Mobile to base station Base station to mobile |
| 5 | Satellite communication | 5.925 - 6.425 $GHz$ 3.7 - 4.2 $GHz$ | Uplink Downlink |
