001-5006-000_FCC.docx
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2.5.3
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.
2.5.4
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 2.4 - Antenna Types
Omni (Vertical Collinear)
Yagi
Vertical Dipole
2.5.5
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.
2.5.6
RF Exposure Compliance Requirements
The Guardian radio is intended for use in the Industrial Monitoring and Control and SCADA
markets. The Guardian unit must be professionally installed and must ensure a minimum
separation distance listed in the table below between the radiating structure and any
person. An antenna mounted on a pole or tower is the typical installation and in rare
instances, a 1/2-wave whip antenna is used.
