ADTRAN 2 x E1 user manual CO-LOCATING Multiple Systems, Antenna Alignment, Rf Low

61280004L2-1C

Section 2 Installation

CO-LOCATING MULTIPLE SYSTEMS

When multiple transmitters are to be co-located (installed in the same equipment room or on the same tower), it is advised to set all systems as follows:

1.If more than one system in the same frequency band is transmitting from the same location, set the antenna polarity of one system horizontal and the other system(s) vertical. (The antennas should be marked as to which mounting position is vertical or horizontal.) This will provide approximately 30 dB of isolation between the different antennas.

2.If more than one TRACER system is installed, set the co-located transmitters to the same frequency plan (example: Plan A or Plan B) and set each to a different spreading code. This keeps the transmitters on the additional system(s) from interfering with the co-located receiver(s).

3.If the systems are from different manufacturers, set the transmit frequencies as close as possible with different spreading codes. Other manufacturers may not use the exact frequency plans as the TRACER system, but keeping the frequencies close will reduce the probability of the transmitter(s) interfering with the co-located receiver(s).

ANTENNA ALIGNMENT

After the transmitter power for each end has been adjusted and the BBP and RFC have been installed and connected, the antenna should be connected to the RFC via the feedline. Verify that both antennas are arranged on the same polarity: vertical or horizontal. The antennas should be aimed toward one another as precisely as possible and the received signal strength indicator (RSSI) voltage measured. The RSSI voltage is a function of the signal strength at the receiver and is used to measure the received signal strength. RSSI varies approximately from 0 to >4 volts, with 0 volts corresponding to a weaker received signal and 4 volts or better corresponding to a stronger received signal.

NOTE

The voltage level present at the RSSI test point represents a relative signal level of receive strength from the far end. No direct correlation can be made between RSSI voltage level and actual receive level in dBm. This test point is provided to assess relative signal level for alignment of antenna.

RF LOW

The “RF Low” LED indicates that the received signal is within 10dB of the minimum received signal strength (RSL < approximately -80 dBm). If this indicator is on, the link performance may be marginal. The antennas should be peaked in azimuth and elevation until the desired signal level is achieved. RSSI may be monitored on either the RF unit or the front of the BBP. If the received signal is too strong and RSSI reaches a maximum such that the peak cannot be discerned, then the transmitter on the far end should be turned down.

At this point the radio link should be operational. Proper operation can be determined by the status of the “LINK DOWN” LED. If this LED is on, the link is not operational. If this LED is not on, the link is operating. Certain types of interference can cause one end of a path to operate and the other end to fail. In some instances, this may be corrected by swapping the frequency plan at each end, thus avoiding the interference if it is stronger at one end than the other. Changing the spreading code at each end may also allow interference to be mitigated.

22 TRACER 2 x E1 User’s Manual