Codan Radio Radio Repeater Systems Training Guide - Manual (Page 11)

RADIO REPEATER SYSTEM | TRAINING GUIDE
Chapter 1: Repeater System Basics Page 3
DETERMINING FREQUENCIES AND FREQUENCY BAND(S)
The fi rst step in designing a radio system is to decide the frequency band(s) to be used in the system.
Determining the proper frequency band to use could be limited to licensing, environmental or existing
system considerations. The frequency bands differ in noise levels, ranges, skip, and other factors.
VHF Lowband (29 to 50 MHz)
This band is subject to heavy skip – signals bounce off the ionosphere and travel great distances.
There are frequent dead spots, and the signal does not bounce off hills or buildings. It has the most
range and the highest noise level.
VHF Highband (132 to 170 MHz)
There is much less skip, less range, and less noise in this band than VHF lowband. This band also has
fewer dead spots than the VHF lowband.
UHF band (406 to 512 MHz)
This bands range is less than in VHF highband. The signal bounces off hills and buildings well and has
practically no skip interference. It also has fewer dead spots and noise.
800 / 900 MHz band (806 to 960 MHz)
The signal bounces off buildings and hills extremely well and presents little noise. The range is less
than UHF and there is more absorption by foliage.
Licensing requirements are the fi rst consideration in determining frequency band. The different
frequency bands available for licensing are determined by a government agency that usually covers site
licensing and frequency coordination. The FCC (Federal Communications Commission) and Industry
Canada are the government agencies in the United States and Canada respectively.
Frequency band selection can also depend on the environment in which the radio system will be
operating. VHF lowband is used in many industrial applications (eg. gas and oil companies) as well
as some law enforcement applications (eg. highway patrol). VHF highband is widely used in forested
or wilderness areas. UHF and 800 / 900 MHz is typically used in urban areas, and to link VHF sites
together. The government licensing agency can help you determine the proper frequency band if you
are unsure of which band to use.
If a radio system already exists, you must assess your existing radio equipment and frequencies. In
order to use the existing equipment with a repeater system, it must be type approved under your
governments’ regulations for use in a repeater system. Your existing equipment should be capable of
at least two frequency operation. The separation between the two frequencies will, to some extent,
dictate system complexity.