CalAmp GUARDIAN User Manual - page 21
Guardian Manual 001-5006-000 Rev 0
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P a g e
2.4.3 YAGI ANTENNA
At remote locations (not used as a Relay Point), a directional Yagi is generally recommended to minimize
interference to and from other users.
2.4.4 VERTICAL DIPOLES
Vertical dipoles are very often mounted in pairs, or sometimes groups of 3 or 4, to achieve even coverage and to
increase gain. The vertical collinear antenna usually consists of several elements stacked one above the other to
achieve similar results.
Figure 2-3 - Antenna Types
Omni (Vertical Collinear)
Yagi
Vertical Dipole
2.4.5 FEEDLINE
The choice of feedline should be carefully considered. Poor quality coaxial cables should be avoided, as they will
degrade system performance for both transmission and reception. The cable should be kept as short as possible to
minimize signal loss. See
Table 2-1
for a list of feedline recommendations.
Table 2-1 – Transmission Loss (per 100 Feet)
Frequency Range
Cable Type
VHF
UHF
900 MHz
LMR-400
1.5 dB
2.7 dB
3.9 dB
1/2” Heliax
0.68 dB
1.51 dB
2.09 dB
7/8” Heliax
0.37 dB
0.83 dB
1.18 dB
1 5/8” Heliax
0.22 dB
0.51 dB
0.69 dB
Outside cable connections should have a weather kit applied to each connection to prevent moisture. Feedline
connections should be routinely inspected to minimize signal loss through the connection. A 3 dB loss in signal
strength due to cable loss and/or bad connections represents a 50% reduction in signal strength.