Daniels VT-3/140-SWA2, Instruction Manual

Page: 89 / 262

Audio Processor Board Instruction Manual 1-1
1 FM AUDIO PROCESSOR
1.1 Introduction
The MT-3 FM Audio Processor is a versatile circuit board that can provide several types of audio
processing for voice or data transmission.
The following terms are defined:
Table 1 Bandwidth Definition
Term Channel Spacing Rated System Deviation
Wideband 25 kHz or 30 kHz ±5.00 kHz
Narrowband 12.5 kHz or 15 kHz ±2.50 kHz
LTR™ is a trademark of E.F. Johnson Co.
Features include:
•
Automatic level control using a compression amplifier with a 25 dB dynamic range
•
Limiter and Splatter filter that removes noise and harmonics
•
Selectable pre-emphasis or flat audio response
•
Temperature compensated audio output
•
Ability to transmit data and voice switched by a single control line.
•
Backwards compatible with Daniels Electronics MT-2 series transmitters.
•
Direct modulation input for LTR™, DCS, paging and other digital modulations that
require very low frequency modulation to the synthesizer or crystal oscillator module.
•
Separate voice and direct modulation outputs, each individually configurable.
•
Multiple jumpers that can be configured to allow maximum flexibility in routing signals
from inputs to outputs, and disabling selected circuits to reduce operating current.
•
Dual microphone and balanced audio compression circuits.
•
On-board multi-configurable temperature compensation to correct for changes in
transmitter deviation over temperature caused by changing characteristics of synthesizers
and oscillators.
•
A single chip 10th Order Linear Phase Lowpass splatter filter for increased cutoff
attenuation responses needed in today’s narrow band environment.
•
The ability to switch between narrow and wideband through a single control line which
can be externally controlled. This can be useful when configured as a multi-channel
transmitter which uses mixed wide and narrowband frequencies.
•
The ability to easily reconfigure fixed operations from narrow to wideband through
simple jumper settings