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Maximal power level input into the Rx port should not exceed -10 dBm. For links with a radio link rate of 3 Mbps, maximal power level input should not exceed -25 dBm. Table 2-4. European Range Table Table 2-5. USA Range Table 35 TECHNICAL: 0118 931 2233 2.048Mbps Wireless Modem 2.048Mbps Wireless Modem Table 2-6. Maximum (Unregulated) Range Table Antenna Alignment In order to function properly and to provide quality results, the modems on either side of the link must have a stable RF link. The alignment procedure is performed in three steps. First, you visually align the antennas on both sides of the link. Next, you activate the Radio and Line LEDs on the front panels of the units (which show basic synchronization) by a process of adjusting the antennas. Finally, you fine-tune the adjustment of the antenna using the RSSI (Received Signal Strength Indication) measurement procedure, described below. For more information on pre-installation (Site Survey mode) and post-installation tests (Counters and Tracers menu) see Chapter 3. Step-1 Visually Aligning the antennas 1. Loosen the screws on the U-bolt that fasten the antenna to the mast (or the bolts on the wall mount), and slowly move the antenna up and down (elevation) and from side-to-side (azimuth), until the antenna points roughly in the direction of the site on the other side of the link. For long distance links or when it is not possible to see the remote location, use a GPS or a map and a compass for the first alignment. 2. Tighten the screws on the U-bolt (or the bolts on the wall mount). Note: Repeat for each antenna - Rx and Tx on both units. Step 2 –Activating the front panel LEDs Two pairs of LEDs on the 2.048Mbps Wireless Modem front panel are lit when the units are synchronized. When the Radio LEDs are both lit it is an indication that the radio link is synchronized, and when the Line RXD and TXD LEDs are lit it is an indication that the line to the DTE is synchronized. 36 SALES: 0118 965 5100 2.048Mbps Wireless Modem 2.048Mbps Wireless Modem To activate the front panel LEDs: 1. If the LEDs are not lit, loosen the screws on the U-bolt that fasten the Rx and Tx antennas to the last (or the bolts on the wall mount) and slowly move the antennas up and down (elevation) and from side-to-side (azimuth), until all four LEDs are lit (Radio - RX Sync and TX Sync, Line –RXD and TXD). 2. Tighten the screws on the U-bolt (or the bolts on the wall mount). Step 3 – Fine tuning the adjustment of the antenna using RSSI Measurement The RSSI (Receive Signal Strength Indicator) enables to fine-tune antenna alignment by supplying a measured value of the signal received by the unit. Maximizing the RSSI value optimises performance. The RSSI value can be viewed using the local monitor, as described on page 72. The RSSI per channel feature displays in graphic format the strength of the received signal on each of the RF channels in use. The modem also enables to collect a measurement of the average RSSI using a DVM (digital voltmeter) connected to the RSSI test pin in the rear panel of the unit. The measured DC voltage is relative to the RSSI value as indicated in Figure 2-15. The 2.048Mbps Wireless Modem enables to perform RSSI measurement using a DVM also near the Receive Antenna. This procedure simplifies the tuning process, by allowing easier reading of the RSSI level while moving the antenna. The RSSI measurement (with DVM or monitor) indicates the strength of reception. In order to maximize the reception strength, the receive antenna and the transmit antenna on the remote site of the link must be aligned facing each other until maximum signal quality is obtained. This procedure should be repeated on the modems on both sides of the link. Note: The RSSI measurement indicates the strength of received signal in the 2.4 -2.5 GHz band. Verify that you are not aligning the antenna towards an undesired source of energy in this band (See also page 82). . To fine-tune the antenna alignment using a DVM connected directly to the unit: 1. Connect one of the DVM probes to the RSSI test pin. Connect the other probe to the case chassis. Figure 2-14. RSSI measurement connection diagram 37 TECHNICAL: 0118 931 2233 2.048Mbps Wireless Modem 2.048Mbps Wireless Modem 2. Loosen the screws on the U-bolt that fasten the receive antenna to the mast (or the bolts on the wall mount) and slowly move the antenna up and down (elevation) and from side-to-side (azimuth) until you receive a maximum RSSI reading on the DVM. (See Figure 2-15). 3. Tighten the screws on the U-bolt (or the bolts on the wall mount). Figure 2-15. RSSI test point accuracy. . To fine-tune the antenna alignment using a DVM near the receive antenna: The modems can be configured send a DC signal through the RCV antenna connector. This signal is proportional to the RSSI voltage, which is present at the RSSI output on the rear panel. 1. Set a Bias-T connection before the Receive Antenna. Figure 2-16. A Bias-T connection for RSSI...

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