MDT Construction Manual ā Issue 2 Page 2
CONTENTS
1 Introduction .............................................................................................................................................................. 4
2 DSB vs SSB ................................................................................................................................................................. 5
3 DSB transmitter ....................................................................................................................................................... 6
4 Direct Conversion receiver ................................................................................................................................. 7
5 MDT Block Diagram ............................................................................................................................................... 8
6 Circuit Description ................................................................................................................................................. 9
6.1 Variable Frequency Oscillator (VFO) ........................................................................................................................ 9
6.2 Mixer ....................................................................................................................................................................................... 9
6.3 Microphone amplifier ................................................................................................................................................... 10
6.4 Transmit amplifier ......................................................................................................................................................... 10
6.5 Power Supply and RX/TX switching ...................................................................................................................... 11
6.6 Receive audio .................................................................................................................................................................... 11
7 Kit Supplied Parts ................................................................................................................................................ 17
8 Individual Parts List ............................................................................................................................................ 19
9 Construction ........................................................................................................................................................... 21
9.1 General ................................................................................................................................................................................ 21
9.2 Building the PCB.............................................................................................................................................................. 22
10 Final Assembly ...................................................................................................................................................... 33
10.1 Microphone socket ......................................................................................................................................................... 33
10.2 Terminating plugs .......................................................................................................................................................... 34
10.3 Front Panel ........................................................................................................................................................................ 35
10.4 Mounting the PCB ........................................................................................................................................................... 35
11 Testing and alignment ....................................................................................................................................... 36
11.1 General ................................................................................................................................................................................ 36
11.2 Power on ............................................................................................................................................................................. 36
11.3 Receive ................................................................................................................................................................................ 36
11.4 Transmit ............................................................................................................................................................................. 37
11.5 Marking the VFO scale .................................................................................................................................................. 38
12 Modifications ......................................................................................................................................................... 40
12.1 Setting the VFO range ................................................................................................................................................... 40
12.2 Receiver alignment ........................................................................................................................................................ 40
12.3 Crystal operation ............................................................................................................................................................ 40
12.4 Using a loudspeaker ...................................................................................................................................................... 40
13 Operation................................................................................................................................................................. 41
13.1 Setting up ........................................................................................................................................................................... 41
13.2 Receiving ............................................................................................................................................................................ 41
13.2.1 SSB .......................................................................................................................................................... 41
13.2.2 CW ........................................................................................................................................................... 41
13.3 Transmitting ..................................................................................................................................................................... 42
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