ADTRAN 4206 Plan A, 4106 Plan A system manual Antenna Gain, Transmitted Power PT

TRACER 4106/4206 System Manual Section 2 Microwave Path Engineering Basics

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Figure 1. Example Microwave Path with Parameters

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.

Table 1. Antenna Gain for Given Dish Diameters

Dish Diameter	Gain at 2.4 GHz	Gain at 5.8 GHz
(in feet)	(in dBi)	(in dBi)
2	21	28.5
4	27	34.2
6	31	37.5
8	33	40.7
10	35	42.5
12	37	44.2

Transmitted Power (PT)

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.

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