User's Manual

The first mixer stage on the BSA amplifier board, which is controlled by a
synthesizer, converts the received frequency down to the IF frequency.
The signal is then filtered by a SAW bandpass filter and, not shown in the
figure, amplified before it is fed to the second mixer stage, controlled by
the same synthesizer as the previous one, for converting back to the
original frequency.
The SAW filter can be either fixed or adjustable depending on the BSA
board used. If the BSA board has fixed band width, this SAW filter is
fixed and selected for the current band width. If the BSA board has
adjustable band width, the SAW filter can be software changed from
within OMT32 (or OMS) to cover various band widths.
The following power amplifier is controlled by the CU. The output gain
can be reduced to avoid instability due to poor antenna isolation.
A detector on the PA board measures continuously the output level. The
signal from this detector is used by the automatic gain control, AGC, to
supervise and, if necessary, reduce the output power to keep it under a
maximum level. The AGC gain control affects all the amplification stages.
The output signal passes duplex filter (DPX) and a directional coupler
(DC) before it is fed to the repeater MS antenna.
ALLGON System AB AR Repeaters & OMT32 Hardware – Functional Description
User’s Manual VD202 90/EN Rev. 1A 1999-07 5 - 15