Microhard Systems IP920, Operating Manual, Page: 59 / 73

IP920 Operating Manual: Chapter 5 Installation
49
To comply with FCC regulations,
.you must limit ERP to 36 dBm or
less.
Antenna
Before choosing an antenna, you should have some knowledge of the path
loss and the topology of the equipment. If the equipment is in a fixed
location and is to communicate with only one other unit also in a fixed
location, then a Yagi antenna is suitable. Choose a Yagi with enough gain
to ensure adequate gain margin. When deploying the Yagi, point the
antenna towards the intended target, ensuring the antenna elements are
perpendicular to the ground for vertical polarization.
In applications where there are multiple units that you must communicate
with or unit, which are in motion, you may select an Omni-directional
antenna with appropriate gain.
See appendix A for a list of approved antennas that can be used with
the IP920 radio modem. If you require another type of antenna please
contact Microhard Systems Inc. The IP920 CANNOT be used with any
antenna that does not appear in Appendix A.
Microhard Systems Inc. can provide you with approved antennas to ensure
FCC and Industry Canada compliance.
FCC Regulations allow up to 36dBm effective radiated power (ERP).
Therefore, the sum of the transmitted power (in dBm), the cabling loss
and the antenna gain cannot exceed 36dBm with respect to the isotropic
radiator.
ERP is calculated as follows:
ERP = Tx Power (dBm) - Cable/Connector Loss (dB) + Antenna Gain (dBi)
Antenna Gains must be in dBi when calculating the 36dBm ERP limit.
1dBd = 2.15dBi
Use the guidelines in the previous section for calculating cable and
connector losses. If cabling and connector losses are 2 dB, then the
maximum allowable gain of the antenna will be 8 dB.