Chapter 3
Tropos Mobile Mesh Router Installation Guide Models 4310-XA and 4319-XA
17
Attenuation with External Antennas
If external antennas are used, it is necessary to adjust the transmit power attenuation to provide
the correct power level for the router. Use the following formulas to compute the required
attenuation level:
Gain’ (dBi) = Antenna Gain (dBi) - Cable Loss (dB)
802.11b/g:
4.9 GHz Antenna
The information in this section applies to the Tropos 4319-XA router.
Note
Operation in the 4.9 GHz band requires an FCC license. The following eligibility rules are specified in Part
90.1203 of the FCC rules:
• Entities providing public safety services as defined under section 90.523 are eligible to hold an FCC
license for systems operating in the 4940-4990 MHz band. All of the requirements and conditions set
forth in that section also govern authorizations in the 4940-4990 MHz band.
• 4.9 GHz band licensees may enter into sharing agreements or other arrangements for use of the
spectrum with entities that do not meet these eligibility requirements. However, all applications in the
band are limited to operations in support of public safety.
Note
To reduce potential radio interference to other users, the antenna type and its gain should be so chosen
that the Effective Isotropic Radiated Power (EIRP) is not more than that permitted for successful
communication.
Tx Antenna Setting (dB) =
0
Gain’ - 7
if Gain’ < 7 dBi
if Gain’ > 7dBi
Table 11 802.11a Antenna Configurations for Public Safety (4940-4990 MHz)
Antenna
Ordering
Number
Channel
Bandwidth /
Operating
Frequency (MHz)
Measured
Conducted
Power (dBm)
Tx
Attenuation
Software
Setting (dB)
Approximate
EIRP (dBm)
9.0dBi omni, magnetic
mount
AN090049
20
4950 - 4980
20.0
4
29.0
