1.
Multichannel Frequency Spectrum Use.
a. Multichannel radio sets use only a selected portion of the frequency spectrum. The
lowest frequency used is 30 MHz in the very high frequency (VHF) range and the highest is 15
GHz in the super high frequency (SF) range. The VHF/ultra high frequency (UHF) bands cover
frequencies from 30 to 300 MHz and 300 to 3000 MHz. The SHF band covers frequencies from
3000 MHz (3 GHz) to 30,000 MHz (30 GHz). The radio systems using these bands normally
require a LOS path between the transmitting and receiving antennas. Tactical multichannel
systems using these frequency bands are normally limited to 25 to 50 miles in a single link
(Figure 2-1A).
b. Radio sets using troposcatter propagation use the 4.4 to 5.0 GHz portion of the SHF
band. These radio sets do not require a LOS path between the transmitting and receiving
antennas because their radio waves are reflected off the troposphere (6 to 10 miles above the
Earth) and have a 100-300 mile operational range for a single link (Figure 2-1B).
Figure 2-1. Transmitting and receiving antennas
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