Where to Get the Signals from a MASTR II

Pin 4 is the audio input connection point (Mic Hi), Pin 2 is the audio input ground (Mic low).  Pin 4 has a +10V bias applied which powered the microphone preamp. Depending on your repeater controller, you may need to insert a DC blocking capacitor.  If you are going to use a mic on the control head, you should insert a resistor in series with the controller's audio output to prevent the controller from loading down the microphone's output, a 5K resister should do it.

Pin 20 is the un-squelched (and is not de-emphasized) audio output and offers around 1 V peek to peek RMS.  You may have to add a decoupling CAP to this line depending on your repeater controller’s audio input circuit.  You may also have to add a resistor in series to reduce the loading on the discriminator.  My advise is to add a RC circuit to de-emphasize the audio if your repeater controller does not have it built in, this will eliminate the tinny sound.  Wire one side of the 15K resistor to pin 20, and the other side to one side of a .22µF capacitor. Ground the other leg of the capacitor. Take the receiver audio from the capacitor-resistor junction.   Pin 18 is the audio output ground. Optionally you can tap audio out from Pin 19 which is the volume control arm. The down fall of this source is that the audio level tracks with the volume control.

Pin 25 is the PTT line, take this line to ground to force the transmitter to on. You will need a circuit which can sink 75 ma of current.

Pin 16 is the CAS (carrier active sensor). It will go to around 10 volts (active high) when the receiver is un-squelched.

Pin 21 is A- and a good place to tap for you signal ground.

Want to add PL encode and/or decode? P908 is the place to do it. Pin 1 is the same as Pin 20 and a ideal place to feed your PL decoder’s input. Pin 4 offers 10 VDC+ and Pin 9 is A-, nice place to take power for your encoder/decoder. Pin 7 is the PL injection point, you can set the PL deviation level by a pot on the exciter board.

I mounted a DB9 female to the front left side of the radio in a small open space and brought out all of the signals on the DB9.