User's Manual

TReX User Manual v2.14 Firmware
Antenna Elevation
As with any radio receiver, raising the height of either the transmitter or receiver antenna will
result in dramatic improvements to the maximum possible receive distance. Although a high
power transmission will increase distance, the installed height of the receiver antenna is the
key to a high performing system.
When close to the ground the major obstacle to overcome, since radio signals are mainly “line
of sight”, is the curvature of the earth. The typical distance to expect can be approximately
calculated as follows:
D =
√
2 r
0
h
f
6076.1 β
0
Where:
D
is the distance to the horizon in NM,
r
0
is the mean radius of the earth (3440.1 NM),
h
f
is the height of your antenna,
β
0
(0.8279) accounts for terrestrial refraction.
This formula can be simplified to:
d = 1.17 ∗
√
h
f
Where:
d
= range in nautical miles,
h
f
= the height of your antenna in feet.
Working with metric units this formula becomes:
km = 2.17 ∗
√
0.305 ∗ h
m
Where:
km
= range in kilometres,
h
m
= the height of your antenna in metres.
Therefore:
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