ADTRAN 4206 Plan A, 4106 Plan A Antenna Information, Antenna Alignment, Tracer Rssi Test Points

TRACER 4106/4206 System Manual Section 2 Microwave Path Engineering Basics

6.ANTENNA INFORMATION

The overall wireless system is directly affected by the antenna selection and installation. The following sections discuss several factors concerning antenna selection and installation.

Verify the antenna installation meets all regulations specified in the National Electric Code (NEC) Article 810.

Antenna Alignment

With line-of-sight microwave communications, optimum system performance requires that the transmitting and 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 a vertical plane). A received signal strength indicator (RSSI) aids the equipment installer in determining when alignment is maximized by simply ensuring maximum RSSI.

TRACER RSSI Test Points

The RSSI indicator for the TRACER 4106/4206 system is provided through the VT100 terminal menus accessed 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 receive power 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 this test point can vary from approximatly 0 to 5 Volts DC. An RSSI Calibration sheet is shipped with the system to provide the installer a cross-reference between actual received signal level (in dBm) and RSSI voltage. This sheet is useful for verifying link budget calculations and ensuring proper equipment installation.

Antenna Beam Patterns

Directly related to the subject of antenna alignment is the topic of antenna beam patterns. Antennas used with the TRACER 4106/4206 system have a particular beam shape determined in part by the physical construction and geometry of the antenna. The antenna beam patterns are characterized by a dominant main lobe, which is the preferred lobe to use for point-to-point communications, and several side lobes, as shown in Figure 1. When setting up a microwave link, antenna alignment is nothing more than steering the main lobes of both antennas until the main lobe of one transmitter is centered on the receiving element of the receiving antenna.

Figure 2. Typical Antenna Beam Pattern

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