Introduction - ozQRP MST3 Construction And Operation Manual

1 I
NTRODUCTION
The MST3 (Minimalist Sideband Transceiver series 3) is the next stage in the evolution of the
MST mono-band transceiver board.
While maintaining the minimalist approach of simple design, easy to build yet with good
performance, the MST3 takes the concept further by adding new features and performance
enhancements. These include:
1. Plug-in band modules, so that a single MST3 can be converted to another band easily
and quickly.
2. Switch input to shift the carrier frequency for USB and LSB operation.
3. Power supply reverse voltage protection using an on-board power MOSFET.
4. A new Intelligent Tone Module (ITM) forms a central role in the MST3, generating
audible tones and controlling the TX/RX switching:
a. CW operation. A good quality 800Hz sinewave is injected into the microphone
circuit when the Morse key is pressed. Adjustable volume sidetone is also heard
in the speaker.
b. Test and alignment. Three tone sequences can be selected using the Tone
button. A Morse test message including a callsign, a stepped frequency sweep
and a continuous tone.
c. Operator feedback. Changing between CW and SSB states is announced with a
Morse code message.
d. MST3 ident. Pressing the Tone button while in SSB transmit state will generate a
'MST3' CW message to identify with other MST3 users.
e. Power on indication. Two short beeps are generated at each power up to
indicate the microcontroller has booted successfully.
f. Callsign store. This is transmitted in Morse code during the test tone sequence.
This is entered using a Morse key.
With the addition of a VFO, an enclosure and a hand full of parts you have a complete and
working SSB transceiver.
Full kits of parts for the MST3 transceiver board and plug-in band filter sets are available from
www.ozQRP.com.
MST3 Construction and Operation Manual – Issue 1 Page 5