Antenna Gain; Transmitted Power (P T ); Figure 1. Example Microwave Path With Parameters; Table 1. Antenna Gain For Given Dish Diameters - ADTRAN TRACER 4106 Plan A System Manual

TRACER 4106/4206 System Manual
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T
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P
T
The following sections further discuss the power budget analysis and its components.

Antenna Gain

Actual transmit and receive antenna gain values depend strictly upon the physical characteristics of the
antennas installed for each link. In other words, the size of the dish determines the antenna gain. Using a
parabolic dish antenna results in the best performance. Antenna gains are specified in terms of decibels of
gain referenced to an isotropic source (dBi). An isotropic source is a hypothetical antenna having equal
radiation in all directions. Typical antenna gains are listed in Table 1; however, dish manufacturers can
provide gains for specific types of antennas.
Transmitted Power (P
The FCC specifies the maximum transmitter power that may be used for antennae of a given gain. FCC
Rules Part 15, Subpart 247 allow for a maximum power of 1 Watt (30 dBm) into antennae of a gain less
than or equal to 6 dBi. At 2.4 GHz (TRACER 4106), the 1-watt maximum transmitter power must be
reduced by 1 dB for every 3 dB of antenna gain over 6 dBi. Since the TRACER 4106 maximum transmit
power is 100 milliwatts, only antennas with gains above 36 dBi (12-foot diameter parabolic dishes) require
any reduction in transmit power. For the 5.8 GHz band (TRACER 4206), there is no reduction in
transmitter output power required for antenna gains greater than 6 dBi.
612804206L2-1A

Figure 1. Example Microwave Path with Parameters

Table 1. Antenna Gain for Given Dish Diameters

Dish Diameter Gain at 2.4 GHz
(in feet)
2
4
6
8
10
12
)
T
© 2004 ADTRAN, Inc.
Section 2 Microwave Path Engineering Basics
d, L
P
Gain at 5.8 GHz
(in dBi) (in dBi)
21 28.5
27 34.2
31 37.5
33 40.7
35 42.5
37 44.2
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