Codan Radio Communications VT-3-150-SN User Manual
2-2
Audio Processor Board Instruction Manual
using the lower input levels) Like the microphone input, the balance input is limited and filtered and
is output at the standard modulation output port.
If no compression is required (i.e.: customer is providing their own), JU11 can be enabled
providing a path through R48 (Auxiliary Input Level Control) to amplifier U2C where pre-
emphasis or flat audio can then be selected from its output.
is output at the standard modulation output port.
If no compression is required (i.e.: customer is providing their own), JU11 can be enabled
providing a path through R48 (Auxiliary Input Level Control) to amplifier U2C where pre-
emphasis or flat audio can then be selected from its output.
2.6
Auxiliary Input
The auxiliary input is a special input and does not have an ALC. This input can be configured for a
pre-emphasis response (enable JU9Y) or a flat-audio response (enable JU9X). The level for this
input is set by R48. The auxiliary output is normally summed with the voice signals by op-amp
U3A, limited, then filtered and output at the standard modulation output port. When jumper JU6 is
disabled and jumper JU7 is enabled, the auxiliary input can be used to directly modulate the
transmitter. Care should be taken when directly modulating the transmitter with the auxiliary input
because the MT-3 transmitters use direct FM modulation and there is no filtering or limiting action
provided by the auxiliary input. The input level to the auxiliary input should be -18 dBm and can
be driven by one of three inputs:
pre-emphasis response (enable JU9Y) or a flat-audio response (enable JU9X). The level for this
input is set by R48. The auxiliary output is normally summed with the voice signals by op-amp
U3A, limited, then filtered and output at the standard modulation output port. When jumper JU6 is
disabled and jumper JU7 is enabled, the auxiliary input can be used to directly modulate the
transmitter. Care should be taken when directly modulating the transmitter with the auxiliary input
because the MT-3 transmitters use direct FM modulation and there is no filtering or limiting action
provided by the auxiliary input. The input level to the auxiliary input should be -18 dBm and can
be driven by one of three inputs:
•
the balanced input – JU11
•
the tone/digital input – JU12 X or Y enabled
•
the direct modulation input – through JU28
When the 600 ohm balanced input is connected to the auxiliary input, the balanced input level
control can be used to adjust the level for the auxiliary input.
control can be used to adjust the level for the auxiliary input.
2.7
Subtone Inputs
There are two subtone inputs available on the FM Audio Processor. Both subtone inputs can be
individually configured to be output from the standard Modulation Output port or to be output from
the Low Frequency / Direct Modulation Output. In standard configuration, Subtone 1 is summed
with the voice signals to be output from the standard Modulation Output port while Subtone 2 is
used for DCS. Both subtone inputs have an input level control.
individually configured to be output from the standard Modulation Output port or to be output from
the Low Frequency / Direct Modulation Output. In standard configuration, Subtone 1 is summed
with the voice signals to be output from the standard Modulation Output port while Subtone 2 is
used for DCS. Both subtone inputs have an input level control.
2.8
Direct Modulation Input
The Direct Modulation Input is an extremely versatile input. This port is designed to be used for
data signals. Depending on the application, the signal can be amplified, AC or DC coupled and
output to the Modulation Output or the Low Frequency / Direct Modulation Output port. Please
consult the factory for specific jumper settings for your application.
data signals. Depending on the application, the signal can be amplified, AC or DC coupled and
output to the Modulation Output or the Low Frequency / Direct Modulation Output port. Please
consult the factory for specific jumper settings for your application.