User manual

ENG COMMUNICATION PORTS AND GPI/O WIRING
Page 40
19.8 MPX AND AUX CONNECTIONS (available only on FM version)
The AUX 1, AUX2 and AUX 3 inputs (BNC connector, 10 kΩ impedance) allow external signals (tipically
RDS) from external encoders to be injected on the MPX output of the processor.
The input gain of the injected signals may be set by means of J1, J2 and J3 jumpers to 0 dB or to – 20 dB.
Factory preset is - 20dB gain for AUX 1 and AUX 2, while AUX 3 is factory preset to 0 dB gain.
Anyway, gains may be altered to 0 dB (- 20 dB) by moving the respective Jumpers J1, J2 and J3 on the MPX
output board.
The processor can mix SCA signals of any frequency with its own MPX signal, as long as
the former are compatible with the composite stereo signal and RDS signal spectra.
The MPX OUT 1 and MPX OUT 2 (BNC connector) provide the FM composite signal + any RDS signal
(internally generated or injected from an external encoder) and SCA signal. MPX OUT 2 output can be
reconfigured in software as a Pilot Reference Output useful for RDS (RBDS) subcarrier generators that
require an external sync reference.
Two attenuation switches (fully configurable) are provided on the processor to deal with
changing RDS/SCA input signals. Using the attenuators (applied to the internally
sourced MPX signal) will reduce the overall level of the signal output from the processor.
See the Chapter (MPX OUTPUT calibration & Setup).
Remarks:
• The stereo multiplex output level is adjusted by software. Factory preset is 0 dBm, i.e. approximately 2.2
Vpp.
• The output impedance of the BNC jack is approximately 10 ohms sourced by an output driver capable to
drive 600 Ohm loads (typical). Maximum performance is achievable when using up to 10 meters of RG-58
cable. Alternatively, 75 Ohm cable may also used for short runs.
• Contrary to Left / Right audio outputs, pre-emphasis is always present on the MPX output and you
can NOT disable it. Nevertheless, You may set the pre-emphasis time to 50 or 75µ sec.
• The 19 kHz pilot phase and level may be adjusted via the control software.
• MPX Out provide various reference tones consisting for easier transmitting chain set-up. To enable the
reference tone, see Pc control software operation
• Each MPX output is individually buffered so that a short circuit on one output will not affect the other.
The SYNC OUT (BNC connector) outputs a 19KHz / 5Vpp square wave for external equipment
synchronization (i.e. RDS encoders). The Sync output must be enabled via the control software