User Manual

MHX-920 Operating Manual: Chapter 5 Installation 39
5. Installation
The installation, removal
or maintenance of all
antenna components must
be carried out by
qualified and experienced
personnel.
The installation, removal or maintenance of all antenna
components must be carried out by qualified and
experienced personel.
The MHX-920 complies with FCC part 15 at the modular level for
operation in the license-free 902-928 MHz ISM band. This chapter
provides guidelines for installing and deploying equipment which
incorporates the MHX-920 module.
5.1 Estimating the Gain Margin
Successful communication between MHX-920 modules is dependent on
three main factors:
• System Gain
• Path Loss
• Interference
System gain is a calculation in dB describing the performance to be
expected between a transmitter-receiver pair. The number can be calculated
based on knowledge of the equipment being deployed. The following four
factors make up a system gain calculation:
1. Transmitter power (user selectable 0, 10, 20 or 30 dBm)
2. Transmitter gain (transmitting antenna gain minus cabling loss between
the transmitting antenna and the MHX-920 module)
3. Receiver gain (Receiving antenna gain minus cabling loss between the
receiving antenna and the module)
4. Receiver sensitivity (Specified as -105 dBm on the MHX-920 module)
In the following illustration, the transmitting antenna has a gain of 6 dB, and
the receiving antenna has a gain of 3 dB. The cable loss between the
module and the antenna is 2 dB on both the transmitting and receiving side.
Transmitter
30 dBm
Output Power
Receiver
Sensitivity =
-105 dBm
Cable Loss = 2 dBCable Loss = 2 dB
Antenna Gain = 6 dB
Antenna Gain = 3 dB
The power level has been set to 30 dBm (1W) on the transmitter, and the
receiver sensitivity for the MHX-920 is -105 dBm.
System gain would be calculated to be:
30 - 2 + 6 + 3 - 2 + 105 = 140 dB.