Operation; Power On; Receive State - ozQRP MST3 Construction And Operation Manual

14 O
PERATION
14.1 P O
OWER N
To power the MST3 you will need a DC power supply or battery. The voltage should ideally be
13.8V for the rated power output, however the supply can range from 12 to 15V. The power
supply is connected to the screw terminal block on the PCB. The MST3 incorporates polarity
protection, so if nothing powers up, check you have the wires the right way. Reverse
connections will not harm the MST3.
When power is applied and the ITM boots up two short beeps will be heard in the speaker.
14.2 R
ECEIVE STATE
At power on the MST3 is automatically placed in receive state. The relay will be de-energized
and the antenna will be connected to the receiver.
Use the controls on the VFO to tune across the band and adjust the audio volume with the AF
gain control. The MST3 incorporates a form of automatic gain control (AGC) where the audio
level to the speaker is limited for input signals above about S9 level. This is performed in the
audio power amplifier which is after the AF gain control. Advancing the AF gain control will not
seem to act in the normal way for large signals, as the AGC circuit will attempt to keep the
speaker level constant. For signals less than S9 the AF gain control will act in the normal way as
the AGC circuit has not been activated.
If for some reason you don't want AGC rotate the AGC trimpot fully counter-clockwise.
MST3 Construction and Operation Manual – Issue 1 Page 57