RC Systems ViewSmart 1600+, Operation Manual

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UM-1097
Revision B 125
Appendix 5 Antenna Selection
Antenna Transmission Range
The distance radio signals can travel is dependent upon several factors including antenna design,
transmitter power and free-space losses.
In order for a wireless link to work, the available system
operating margin (TX power - RX Sensi Antenna gains) must exceed the free-space loss and all
other losses in the system. For best RF line-of-site, the combined height of both antennas must exceed
the Fresnel
zone diameter.
Distance Between antennas Fresnel Zone Diameter Freespace Loss (dB)
1000ft (300m) 16ft (4.9m) 81
1 mile (1.6km) 32ft (9.7m) 96
5 miles (8km) 68ft (20.7m) 110
Example:
A 2.4GHz WaveNet system has following parameters:
•
RF TX power setting = 21 dBm (125 mW)
•
RF RX sensitivity = -95 dBm (this is a constant)
•
Antenna gain (standard equipped rubber collinear) = 7dBi x 2 = 14dBi
So, the system operating margin is 21 - (-95) + 14 = 130 dBm. This is enough to transmit 5 miles if free-
space was the only loss in the system. For this to be the case, the antennas must be mounted with a
combined height greater than 68ft above all obstructions (including the ground) to keep the Fresnel
recommended there be at least 20dB extra system operating margin.
RF “Rules of Thumb”:
•
Doubling the range with good RF “Line of Sight” (LOS) requires an increase of 6 dB.
•
Doubling the range without good RF LOS requires an increase of 12 dB.
•
Doubling the power increases dBm by 3.
Antenna Selection and Location
The location of the antenna is very important. Ensure the area surrounding the proposed location is clear
of objects such as other antennas, trees or power lines which may affect the antenna’s performance and
efficiency. It is also vital that you ensure the support structure and mounting arrangement is adequate to
support the antenna under all anticipated environmental conditions. The choice of appropriate mounting
hardware is also important for both minimizing corrosion and maintaining site intermodulation
performance.
Most installations with ranges under 1000 feet require only the standard equipped rubber antennas.
Distances up to 2 miles may be achieved by using YAGI directional antennas aimed towards a mast