ADTRAN TRACER 4106 Plan A System Manual

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TRACER 4106/4206 System Manual Section 2 Microwave Path Engineering Basics612804206L2-1A © 2004 ADTRAN, Inc. 216. ANTENNA INFORMATIONThe overall wireless system is directly affected by the antenna selection and installation. The followingsections discuss several factors concerning antenna selection and installation.Antenna AlignmentWith line-of-sight microwave communications, optimum system performance requires that the transmittingand receiving antennas are properly aligned. This ensures maximum received signal power at each receiver.Antenna alignment must be achieved in both azimuth (along a horizontal plane) and elevation (along avertical plane). A received signal strength indicator (RSSI) aids the equipment installer in determiningwhen alignment is maximized by simply ensuring maximum RSSI.TRACER RSSI Test PointsThe RSSI indicator for the TRACER 4106/4206 system is provided through the VT100 terminal menusaccessed through the RS-232 interface, and it is presented as a series of bars indicating signal strength.More bars means more RSSI, which ensures more received signal strength and better link performance.If both the local and remote end of the system are operational, the remote TRACER 4106/4206 receivepower can be viewed from the local TRACER 4106/4206 VT100 terminal menu interface.An RSSI test point, located on the front panel, provides a DC voltage level (relative to the GND test point)that corresponds to the amount of signal being received from the far end's transmitter. The voltage at thistest point can vary from approximatly 0 to 5 Volts DC. An RSSI Calibration sheet is shipped with thesystem to provide the installer a cross-reference between actual received signal level (in dBm) and RSSIvoltage. This sheet is useful for verifying link budget calculations and ensuring proper equipmentinstallation.Antenna Beam PatternsDirectly related to the subject of antenna alignment is the topic of antenna beam patterns. Antennas usedwith the TRACER 4106/4206 system have a particular beam shape determined in part by the physicalconstruction and geometry of the antenna. The antenna beam patterns are characterized by a dominant mainlobe, which is the preferred lobe to use for point-to-point communications, and several side lobes, as shownin Figure 1. When setting up a microwave link, antenna alignment is nothing more than steering the mainlobes of both antennas until the main lobe of one transmitter is centered on the receiving element of thereceiving antenna.Figure 2. Typical Antenna Beam PatternVerify the antenna installation meets all regulations specified in the National ElectricCode (NEC) Article 810.