written 7.9 years ago by
teamques10
★ 64k
|
• modified 7.9 years ago |
This question appears in Mumbai University > Mobile communication and computing subject
Marks: 5 M
Year: Dec 15, May 15
|
written 7.9 years ago by
teamques10
★ 64k
|
The transmission over the air (i.e. radio transmission) can take place using many different frequency bands. Each band has its own advantage as well as disadvantage.
The above diagram shows the frequency spectrum used that can be used for data transmission. It starts from 30 Hz and goes upto 300 THz.
Along with the frequencies are show the wavelength of the signals calculated by the formula: λ=c/f where c=speed of light in vacuum i.e. 3.8*108 m/s.
| Band | Range | Details/Application |
|---|---|---|
| Very low frequency | From 3 KHz onwards | They are long waves, having large wavelength |
| Low frequency (LF) | 30 KHz to 300 KHz | Used by submarines due to their water-penetrating ability and can also follow earth’s surface. |
| Medium frequency (MF) | 300 KHz to 3 MHz | Used for radio broadcast using AM/SW/FM modulation techniques.,Also used for aircraft navigation |
| High frequency (HF) | 3 MHz to 30 MHz | Used for radio broadcast using AM/SW/FM modulation techniques.,Also used for aircraft navigation |
| Very,High Frequency (VHF) | 30 MHz to 300 MHz | TV broadcast range begins here:,Used for TV broadcast, Land mobile. |
| Ultra-High Frequency (UHF) | 300MHz to 3 GHz | WLANs, Analog-based mobile phones, cordless telephones, 3G cellular systems etc. |
| Super High Frequency (SHF) | 3 GHz to 30 GHz | Directed microwave links, radar, satellite |
| Extremely High,Frequency (EHF) | 30 GHZ to 300 GHz | Very close to the infrared region; also used for satellite, radar. |
| Infra-red | 3 THz to 30 THz | Used for directed links e.g. to connect different buildings via laser links. |
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