Operation Manual

System Description
36
Repeaters
Bird Technologies offers a wide variety of repeaters to boost off air signals. The repeated signals can feed passive
DAS or can be used as an input into the active DAS.
DMR 400 Series Rack Mount Repeater
The DMR 400 is designed to fit in the Headend Master Frame along with the BIU and FOI cards. The system was
originally designed to be used in moving coverage areas such as ships and trains that require active control over the
downlink gain (link symmetry) to compensate for wide variations in the off-air signals, but the system can easily be
implemented in traditional fixed locations such as offices and hospitals.
Figure 23 DMR 400 Rack Mount Repeater
Although the DMR repeaters are rack mounted with the active DAS components, the DMR repeater can function as
a stand alone unit to provide coverage to a passive DAS.
The DMR repeater family offers link symmetry settings. This function is used to automatically adjust the uplink gain
based on the downlink signal. When installed in moving coverage areas such as trains, the feature prevents the
repeater from desensitizing the donor site by automatically controlling uplink levels.
The DMR repeater also offers self-oscillation protection. This function is used to detect problems with isolation
between the donor and service antenna. The repeater will intervene and lower the gain to a level equal to the
isolation minus the stability margin. The settings are separate for UL and DL.
 On/Off
 Stability margin: Value setting of how much lower the gain should be than the calculated isolation. Range
of 0.0 to 20.0dBm.
 Recovery time: Time that should pass before the repeater reset the gain to the value specified level in “RF
Config” (set gain). Range of 30 to 86,400 seconds.
 Recovery margin: Set value of gain level above the gain specified in “RF Config” (set gain) that is used when
the repeater recovers after the “Recovery Time”. Range of 0.0 to 20.0dBm.
The DMR400 offers variable bandwidths up to 35Mhz, depending on the configuration.
Remote access can be provided via an Ethernet connection or through the Bird Remote Gateway. SNMP is a
standard on the units. No proprietary software is required. Operational parameters are set via a web browser.