DE
DANIELS
ELECTRONICS
2-6
MT-3 AM Transmitter Main Board Instruction Manual
2 . 1 . 5
Amplifier Circuits
The MT-3A series Amplifier has 5 connections that are cabled to the transmitter board: +13.8
Vdc, +9.5 Vdc, Enable, Mod and Gnd. The +13.8 Vdc supply (JP1-3) is always on while the
+9.5 Vdc supply (JP1-2) is always switched by a PTT signal. The enable line (JP1-1) is active
low and is controlled by the Qualified PTT signal from the synthesizer.
Jumpers J12, J13, J14, and J15 are not installed.
2 . 2
MT-3 Front Panel Board
The MT-3 Front Panel Board is a subsection of the MT-3 AM Transmitter Board which is used to
mount the front panel switch, diode, and microphone connector. The main purpose of the board is
to eliminate a wiring harness for the front panel components. Jumper J1, located on the rear of the
circuitboard, is used to select whether or not the MIC PTT line activates the transmitter's TOT:
•Jumper J1:
'x' position
MIC PTT NTO no time-out-timer (factory setting)
'y' position
MIC PTT WTO with time-out-timer
Refer to section 5.3.2 "MT-3 Front Panel Board Schematic Diagram".
2 . 3
MT-3 AM Audio Processor
2 . 3 . 1
General
The MT-3 AM Audio Processor is a versatile circuitboard that can provide several types of audio
processing. The module also has an on-board programmable push-to-talk (PTT) time-out-timer
(TOT) on an attached circuitboard. A cont9.5 Vdc supply and a cont13.8 Vdc
supply together with a sw8.0 Vdc supply are required to power the module. Refer to
section 5.4.1 "MT-3 AM Audio Processor Component Layout" and to section 5.4.2 "MT-3 AM
Audio Processor Schematic Diagram" for component location and designation references.
2 . 3 . 2
Power Requirements
The audio processor can be configured for continuous audio standby or for switched audio standby
by the Transmitter Main Board. If fast audio risetime is desired, the transmitter should be operated
in standby mode 3 or 4 as specified in section 2.1.2.7. The current for the associated TOT is
approximately 4 mA when the transmitter is keyed.
