Over What Distance will Radios Work?
We are frequently asked 'over what distance with radios work'. It is impossible to quote because range is mostly affected by terrain, both the man-made such as buildings and forests and natural such as hills and valleys.
The radio systems suitable to use with hand-held radios use VHF and UHF frequencies. This is because these frequencies offer the best range available for portable radios with manageable sized antennas.
Range with these frequencies is Line-of-sight. This means if you can see the other radio, even miles away you should be able to communicate. Of course if the signal was strictly line-of-sight you would not be able to talk room to room. Actually two other factors come into play;
- Radio signals will penetrate most materials to some extent, bricks, wood and plasterboard. But even thin metal sheets will block nearly all the signal. The thicker the material the less signal gets through. So radios will work through the walls of most buildings but the more walls the weaker the signal becomes.
- Radios signals will reflect off many surfaces they cannot pass through, the metal ones being better reflectors but even hillsides can reflect. These reflections also help signal coverage for example reception into blind valleys.
Typical examples of range with Back-to-Back Systems:
In Building 25m-100m
City centre: 100m to 500m
Suburbs: 200m to 1Km
Rural:Flat Open country: 1km to 5km
Rural: Undulating and hill country:500m to 20+km
This last example is explained by the radios either having high ground obstructing them or each being on a hilltop with nothing in the way.
The first example is explained by some modern buildings often using foil backed plasterboard for energy efficiency and this reduces in-building range significantly.
There are no magic frequencies that work over massive distances in urban or rural areas. It is true that some lower frequencies can transmit halfway around the planet but the have huge aerials, rely on bouncing the signal off layers in the atmosphere and offer very variable qualities of communication which can vary from minute to minute or not at all at certain times of the day. Not at all suitable for easy push -and-talk communications.
There are no makes or models of radios that are significantly better than others although digital licensed radios generally give the very best coverage and low cost licence-free radios the poorest coverage. The only significant way to improve range of hand-held radios is to use a Repeater.
To get the best range please read: Improving Range
