| Tropospheric propagation |
Tropospheric propagation
- overview, tutorial or article about tropospheric propagation and the way
in which radio signals at VHF and above propagate over greater distances than
strictly line of sight in the troposphere
On frequencies above 30 MHz, it is found that the troposphere
has an increasing effect on radio signals and radio communications systems. The
radio signals are able to travel over greater distances than would be suggested
by line of sight calculations. At times conditions change and radio signals may
be detected over distances of 500 or even 1000 km and more. This is normally by
a form of tropospheric enhancement, often called "tropo" for short. At times
signals may even be trapped in an elevated duct in a form of radio signal
propagation known as tropospheric ducting. This can disrupt many radio
communications links (including two way radio communications links) because
interference may be encountered that is not normally there. As a result when
designing a radio communications link or network, this form of interference must
be recognised so that steps can be taken to minimise its effects.
The way in which signals travel at frequencies of VHF and
above is of great importance for those looking at radio coverage of systems such
as cellular telecommunications, mobile radio communications and other wireless
systems as well as other users including radio hams.
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