User's Guide

55
Maximum Permissible Exposure Limits
THIS PRODUCT IS CATEGORICALLY EXCLUDED FROM ROUTINE ENVIRONMENTAL
EVALUATION ACCORDING TO CFR 47, SECTION 1.1037.
Repeaters like the 48900 series generate radio signals and thereby give rise to electromagnetic
fields. The installer is expected to have a complete understanding of CFR Title 47, Sections 1.1307
and 1.1310. A brief discussion follows but is not intended to be a substitute. Additional information
can also be obtained from OET Bulletin 65.
§ Antenna installation should be performed by qualified technicians only.
§ Installation instructions are not optional and are for the purpose of satisfying FCC RF
Exposure Compliance.
§ All antennas (donor and service) are to be fixed-mounted and physically secured to one
location.
§ Maximum donor antenna gain is 28 dB.
§ Non building-mounted donor antennas must be greater than 10 meters above ground.
§ Maximum service area antenna ERP is 1.0 Watt.
§ Minimum separation to any body part of any person is 25cm.
There are two types of antennas attached to this unit. The donor antenna is typically roof mounted
and the service antenna is usually mounted in a publicly accessible area. Both antennas should be
fixed mounted. Installation considerations for both of these will be discussed separately.
Donor antennas receive the base site TX signals and transmit the mobile TX signals back to the base
site (uplink paths). These are typically mounted on rooftops or tower structures. The maximum
composite power of the uplink path is 160 mW (+22dBm). Section 1.307(b)(1) excludes from routine
environmental evaluation, facilities, operations and transmitters that, according to Table 1 (titled
"Cellular Radiotelephone Service"), are less than 1000W ERP for building mounted antennas and
less than 1000W and greater than 10 meters above ground for non building-mounted antennas. As
such, with maximum power from the uplink path @ 160 mW (+22dBm) and a maximum antenna gain
of 28 dB, the donor antenna installation will not exceed 1000 Watts (+60 dBm) and is categorically
excluded.
However, according to Section 1.1307 (b)(1), the appropriate exposure limits of 1.1310 are applicable
to all facilities, operations, and transmitters. Therefore, the MPE (Maximum Permissible Exposure) of
Section 1.1310 applies to the donor antenna installation. OET Bulletin 65 provides methods of
calculating power density based upon the ERP and distance. It would be impossible to cover every
possible configuration in this manual. Likewise, it would be unreasonable to dictate the exact
parameters of every installation; therefore, it is the responsibility of the qualified technician to know
and ensure that Sections 1.1307 and 1.1310 of CFR Title 47 are being met.
The following scenario is a typical rooftop installation in an uncontrolled area (worst-case) using a 18
dB gain donor antenna. The MPE @ 824 MHz is 0.549 mW per cm
2
. The uplink is being driven to its