Motorola Motorola PTP 250, User Manual, Page: 120 / 236

Compliance with radio regulations Chapter 4 Reference information
phn-2182_002v000
4-30
May 2011
Calculating EIRP for connectorized units
When operating with external antennas in countries that impose an EIRP limit, the
administrator has to set the maximum transmit power to ensure that EIRP does not
exceed the limit allowed by regulations.
To calculate the maximum EIRP that the unit can output, use this formula:
Maximum EIRP (dBm) =
Maximum Power Level (dBm) + Antenna Gain (dBi) – Cable Loss (dB)
To calculate the highest permissible setting of Maximum Power Level, use this
formula:
Maximum Power Level (dBm) =
Allowed EIRP (dBm) – Antenna Gain (dBi) + Cable Loss (dB)
Where: Is:
Maximum Power
Level (dBm) the highest permissible setting of the
Maximum Power Level attribute in the
Step 2: Wireless Configuration page
Allowed EIRP
(dBm) the EIRP limit allowed by the regulations
Antenna Gain
(dBi) Antenna Gain as set in the Step 2:
Wireless Configuration page
Cable Loss (dB) Cable Loss as set in the Step 2: Wireless
Configuration page
NOTE
Choose an antenna and RF cable that will not cause the PTP 250 to exceed
Allowed EIRP. As PTP 250 does not support Maximum Power Level settings
below 4 dBm, the maximum antenna gain (allowing for cable loss) is limited
as follows (examples in
Table 4-21 ):
Maximum Antenna Gain (dBi) – Cable Loss (dB) = Allowed EIRP (dBm) – 4
Table 4-21 Maximum permitted antenna gain (allowing for cable loss)
Allowed EIRP Maximum (Antenna Gain - Cable Loss)
30 dBm 26 dBi
36 dBm 32 dBi