Campbell Scientific RF450 Spread Spectrum Radio - Manual (Page 17)

RF450 Spread Spectrum Radio
3.6.8 Transmit Power Setting
This setting specifies the RF transmit power. Use a transmit power of 0 when
bench testing to reduce RF exposure.
The FCC specifies a maximum EIRP (Effective Isotropic Radiated Power) of
36 dBm.
EIRP = (Transmitter Power) + (Antenna Gain) - (Cable Losses) [all in dB or
dBm]
The RF450 maximum power is 30.5 dBm; therefore, a 6 dB (or lower) gain
antenna can be used with any Transmit Power setting. If higher gain antennas
are used, the cable loss will need to be determined, and the Transmit Power
adjusted so as not to exceed the FCC limit of 36 dBm.
Note that lower transmit power can be used (to conserve battery power) if the
required range allows it.
Table 3.6-1 shows the RF450 RF transmit power versus the setting.
TABLE 3.6-1. Transmit Power Settings
RF Transmit
Power Setting
RF Power (dBm)
RF Power (mW)
10 30.5 1122
9 30.0 1000
8 29.5 891
7 28.8 759
6 27.4 550
5 26.4 437
4 24.4 275
3 21.5 141
2 18.2 66
1 12.3 17
0 7.5 6
3.6.9 Low Power Mode Setting
This setting allows a multi-point Slave to consume less power. This is
achieved primarily by dimming the transceiver's LEDs. When set to 2 through
31, the transceiver will sleep between slots. For example, at a setting of 2 the
transceiver sleeps 1 out of 2 slots; at a setting of 3 the transceiver sleeps 2 out
of 3 slots, and so on.
Table 3.6-2 shows the changes at different low power mode settings. The
actual current draw depends on many factors. The table below gives only a
qualitative indication of supply current savings. A low number reduces latency
and a high number reduces current consumption. An optimum setting
(balancing latency and power savings) is 2 or 3.
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