User's Manual

044-05156 Rev C 28
MCR21929-1-2 Subrack Input/Output Connectors
Reference
Number
Name Function
1 DC Power Terminals Base station DC power connections.
2 GROUND Lug Subrack chassis ground.
3 RF OUTPUT Connector
Type-N female coax connector, RF output to TX filter and antenna. See
table A-1 for power output level of one to two amplifier module systems.
4 RF INPUT Connector
SMA female coax connector. RF input from combiner or TX card. See
specifications for power input level.
5 RF SAMPLE Connector SMA female coax connector. ~ –50 dB sample of the subrack RF output.
6 ALARMS Connector
15-pin female D-Sub connector. Permits remote monitoring of amplifier
form-C dry contact alarms.
7 RS-485 Connectors
9-pin female D-Sub connector. Permits remote monitoring of RS-485
signals.
8 PREAMP Connector
9-pin female D-Sub connector. Permits remote monitoring of preamplifier
and DC converter signals.
9 RS-232 Connector
9-pin female D-Sub connector. Permits downloading of software to the
subrack and/or amplifiers.
4.6.2 Automatic Power Control (APC)
The APC is a power limiting function that limits the composite output power to 0.2dB to 1.0dB greater than the rated
power for the inserted MCPA combinations. If the output power of the subrack exceeds an “engage” threshold (see
below) the gain is reduced. The LED indicator located on the top front-right of the subrack blinks when the APC is
engaged. The gain is reduced until the output power complies with the “settle” range threshold. As the input drive
reduces, the gain recovers by the amount needed to approach the nominal output power, until the original gain is
achieved. Any power level in between the nominal and the engage threshold does not warrant a gain change.
APC Limit Thresholds (Watts)(G3S-1900-125)
MCPAs Nominal Engage Settle
1 109 122 112
2 218 244 222
4.6.3 Gain Modes
The subrack can be operated in either standard gain or constant gain mode. The choice of two gain modes
provides system design flexibility. Standard gain is the mode most often selected by system designers and is the
factory default setting of the subrack. Standard gain mode changes the gain of a subrack based on the number of
installed functional modules, while constant gain restricts the gain of the subrack to that of about one module,
regardless of the number of modules installed.
When a given sector is operated at full available power to maximize call capacity or when more system gain is
needed, standard gain mode is best. At lower power level requirements or when a specific system gain value must
be maintained, the system designer may elect to use constant gain mode instead. Constant gain mode maintains a
consistent cell site coverage footprint while allowing N+1 redundancy and increased system reliability. By installing
one more amplifier than the RF power plan requires, Constant gain mode allows for a back-up amplifier, should one
of the cell site’s amplifiers become inoperable.
Standard gain or constant gain is independently selectable on a sector-by-sector basis.
Subrack Gain
Active
Gain Mode
MCPAs Standard
Constant
2 51.5 48
1 48.5 48