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Section 2 Microwave Path Engineering Basics TRACER 6000 Series Integrated System Manual
20 Copyright © 2005 ADTRAN, Inc. 612806420L1-1F
Transmitted Power (P
T
)
The FCC specifies the maximum transmitter power 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 6410), the 1-watt maximum transmitter power must be reduced by 1 dB for
every 3 dB of antenna gain over 6 dBi. This rule is shown in Table 5.
For the 5.8 GHz band (TRACER 6420 L1 and L2), the maximum output power is 1 watt (30 dBm) regardless
of the gain of the attached antenna. Since the TRACER 6420 L1 and L2 maximum transmit powers are
100 milliwatts and 250 milliwatts, respectively, there is no reduction in transmitter output power required.
Carrier Wavelength (λ)
The carrier wavelength is the physical wavelength of the main RF carrier being used for communication, and
is usually approximated at the center frequency of the band (which is 2421.7 MHz for TRACER 6410 and
5787.5 MHz for the TRACER 6420). The carrier wavelength calculations follow.
λ = c / f (meters)
where
c = speed of light (in meters)
f = frequency (in Hz)
resulting in the following carrier wavelengths
TRACER 6410
λ = 3.00 x 10
8
/ 2421.7 x 10
6
= 0.124 m or 12.4 cm
= 4.88 in
Table 5. Transmit Power Reduction for Various Antennae Gains
Output Power
(dBm)
Maximum
Antenna Gain
(dBi)
Maximum EIRP
(dBm)
27 15 42
26 18 44
25 21 46
24 24 48
23 27 50
22 30 52
21 33 54
20 36 56
TRACER 6420
λ = 3.00 x 10
8
/ 5787.5 x 10
6
= 0.0518 m or 5.18 cm
= 2.04 in