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The ranges quoted by the radio manufacturers are for guidance
only. Actual performance will vary either side of this range.
For example PMR446 radios are often quoted as having a range
of 3km
The range over which a radio link will work reliably can
often be hard to predict. To quote a range without knowing
the terrain is usually just a guess.
Range is dependent on many factors. The best range is achieved
in open space well above ground level. Mountain-top to mountain-top
is a good example. This is often referred to as 'line-of-sight'.
(Don't take this literally as radios work just as well in
the dark, cloud or fog!)
'Line-of-sight' range should be considered the absolute
maximum range. As the two radios come nearer to ground level
obstacles on the ground start to absorb some of the radio
signal. Buildings, trees and ground undulations all reduce
range.
In flat country, range may well be less than half line-of-sight.
Absorption is worst with soil, rock and metallic structures.
Avoiding these between the two radios will help improve the
range.
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Sometimes materials that absorb signals will
also reflect them. This can be used to your advantage particularly
in hill country where there maybe a ridge of high ground between
the radios. Reflection from a nearby hill will sometimes bounce
the signal bypassing the obstacle.
Only your own experience will help you predict where radios
won't work, the following briefly sums up the situation.
- At sea or from mountaintop to mountaintop will give the
best range (an exception being in a small boat in a high
swell).
- In very flat country the range will be predictably average
- In hilly country the range will vary from the impressive
to the disappointing.
- Underground and in metal structures range can be poor.
Relocate if range is
poor. A few metres higher will often make a huge difference
to range.
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Over
what distance will radios work?
