VHF (Very High Frequency)
This type of radio has been professionally in
use for many years world-wide and is supported by all Manufacturers of two-way
radios. These radios are typically high-powered but in South Africa the power
limit is restricted to 25W for Commercial use. This is, however, completely
adequate for good radio communications between two or more users.
For our ORRA purposes the radios operate on VHF, which is a range of frequencies
within the 146 - 174MHz band. VHF radios offer excellent communication range,
anywhere from about 15 - 30Km between mobile units but dependent upon
surrounding terrain. They are powered at 25 watt RF output and are immune to
interference caused by atmospheric or electrical conditions. All VHF radios
require an appropriate ICASA license, or, in our case, an ORRA license.
The same rules for AM antennas apply to the FM antennas as well. However, there
are two common types available:
- Quarter Wave Antenna, which should once more be mounted in a central position
on a metal surface or on the B or C pillars of a vehicle. The antenna whip is
only some 400mm or so in length. This is the currently preferred antenna for
ORRA purposes because of the fairly wide spread in the current ORRA frequencies.
Quarter-wave antennas are a good choice in hilly terrain
- 5/8 Antenna, normally, suitable for B or C pillar mounting but can work on a
bull bar. This type of antenna will produce good results when used either for a
single frequency or a group of frequencies clustered in close proximity to one
another. Not suitable for frequencies that are spread far apart from one
another.
Pictured below are some typical multi-channel
VHF/FM Radios. As ORRA has revised their channel list, we will no longer
consider any radio below 8-channel capacity.
KENWOOD TK7100 64-Channel VHF Radio
KIRISUN PT8100 VHF 256-Channel Mobile Radio
VERTEX VX2200 128-Channel VHF Radio
