Answers
What frequency bands are typically used for humanitarian VHF and UHF radio communications?¶
- VHF: from 30Mhz to 300Mhz
- UHF: from 300MHz to 3GHz
Typically:
- 138-144Mhz for VHF
- 400-470Mhz for UHF
What are the key characteristics of VHF compared to UHF?¶
| Property | VHF | UHF |
|---|---|---|
| Range in open terrain | Long | Medium |
| Building penetration | Medium | Good |
| Antenna size | Larger | Smaller |
| Infrastructure needed | Fewer repeaters | More repeaters |
Why are VHF radios often used for longer outdoor distances, while UHF radios may work better inside buildings or dense urban areas?¶
Due to wavelength:
- UHF:
- Shorter wavelength → waves penetrate buildings, walls, and other structures better
- Higher frequency = better indoor or dense urban coverage
- Outdoor range is shorter: waves are more easily absorbed by terrain and vegetation
- VHF:
- Waves can bend around obstacles (diffraction) and follow the curvature of the Earth more effectively
- Less absorption by walls or vegetation, so signals can travel farther outdoors
- Lower frequency = better for open areas like fields, forests, or rural settings.