User's Manual

10 Appendix A: Radio Frequency Basics
The Section covers introductory information on radio frequencies (RF) for those
who have not had to deal with RF in an outdoor environment before.
10.1 The Electromagnetic Spectrum
The electromagnetic waves all have similar physical behavior and their uses
range from AM radio broadcast stations at the low frequencies to TV
broadcasting frequencies, through microwave frequencies and then on to visible
light and X-Rays. These are illustrated in Figure 10-1.
Figure 10-1: The electromagnetic spectrum
Every country has its own assignment of frequency usage, called the Frequency
Allocation Table. The United Nations has committees that try to coordinate
usage within Regions, but each country has the right to “do its own thing”. The
US is in a Region that covers all the Americas (North, Central & South), and
there is a lot of commonality within the Region.
The US Frequency Allocation Table has been put in a chart form, shown in
Figure 10-2. The TV and the 5-GHz bands are highlighted with circles.
The 5-GHz-Band portion of that chart is shown in Figure 10-3. Notice that
segments are allocated to satellite communications, to amateur radio usage
(hams), to radio-location and radio-navigation systems. The location/navigation
category includes radar.
The chart is formatted so that users with higher priority are on top of users with
lesser priority. Unlicensed users have the least priority. In fact, every product
ARCXtend manual, August 2003 10-1