DE
DANIELS
ELECTRONICS
MT-3 AM Transmitter Main Board Instruction Manual
2-5
2 . 1 . 3 . 1
Microphone Audio
Normally the audio from a transmitter's microphone is transmitted by that transmitter; however, the
Transmitter Main Board can be configured by the MIC IN and MIC OUT lines so that the audio
from an external microphone modulates transmitter. The configuration of the MIC IN (pin Z4) and
MIC OUT (pin B4) lines on the MT-3 Transmitter Board are controlled by jumpers J16 and J17
respectively. Jumper J16 selects the audio source for the MT-3 AM Audio Processor's
microphone input. Jumper J17 is used to enable or disable the MIC OUT line. Normally the
transmitter's microphone is selected (J16 in the 'x' position) and the MIC OUT line is enabled (J17
is installed).
2 . 1 . 3 . 2
Received Audio
Pin B20 is the audio input from the transmitter's corresponding receiver. The default setting for
this line is to have it AC coupled (Jumper J9 is out) and directly connected to the front panel board
RX AUDIO line.
2 . 1 . 4
Channel Selection
2 . 1 . 4 . 1
Synthesized Transmitter
Eight backplane connections are used to communicate with the synthesizer unit. Pins D28, D30,
and D32 are used (in house) to program the synthesizer. Channel select lines (pins D20, D22,
D24, and D26) are used once the synthesizer is programmed to select one of 16 channels. If the
channel select lines are all low (channel 0) the channel for the synthesizer is read from switches
FSW1 (most significant), FSW2, FSW3, and FSW4 (least significant). Since the resulting
frequency is dependent on the transmitter model, refer to the section on frequency selection in the
Transmitter Manual or to the channel designation tables for that particular transmitter.
2 . 1 . 4 . 2
Crystal Controlled Transmitter
The crystal control module is a direct replacement for the synthesizer module and therefore uses the
same connections as the synthesizer to connects to the MT-3 AM Transmitter Main Board. The
channel select lines and switches FSW1 to FSW4 are not used by the crystal control module as the
transmitter's operating frequency is determined by the crystal control module's crystal frequency.
A frequency multiplication factor, described in the manual for this module, relates the crystal
frequency to the operating frequency .
