Introduction

This is a page detailing some technical information on the Yaesu SSM-85D microphone.

Yaesu SSM-85D

Pinout

The connector of the microphone is an 6P6C modular connector. The pinout of the SSM-85D can be found by examining the FTM-400 Technical Supplement. In the schematic on Page 14 the jack is pictured (on the right edge between the top and middle).

NOTE: The FTM-300 supplies +8V on pin 4

SSM-85D Pinout

Table of pins and wire colors

Pin Function Wire Color
1 PTT Blue
2 Mic White
3 GND Black (Tinned wire on modular connector)
4 +V Red
5 SW1 Gray
6 SW2 Green

Schematic

While I haven’t found a schematic for the SSM-85D, I did find one for what I understand is its predecessor, the MH-48. While this schematic certainly isn’t identical, it uses a matrix circuit which jives with the voltage observations below.

MH-48 Schematic

PTT Voltages

Supplying the mic with +5V, I connected a 220k pullup resistor to the PTT wire. When the button was not depressed, 4.898V were present. When PTT is pressed, 0.717V are present.

SW1/SW2 voltages

The mic appears to use a keyboard matrix circuit to encode its 23 non-PTT buttons. With +5V applied and a 220k pullup resistor from each of SW1/SW2, here are the voltages found for each key.

Button Row Column SW1 Voltage SW2 Voltage
Up - - 0.675 0.190
Down - - 1.275 0.190
Mute - - 3.081 0.079
1 1 1 0.067 0.563
2 1 2 0.067 1.163
3 1 3 0.067 1.982
A 1 4 0.067 3.224
4 2 1 0.519 0.563
5 2 2 0.519 1.163
6 2 3 0.519 1.982
B 2 4 0.519 3.224
7 3 1 1.145 0.563
8 3 2 1.145 1.163
9 3 3 1.145 1.982
C 3 4 1.145 3.224
* 4 1 1.976 0.563
0 4 2 1.976 1.163
# 4 3 1.976 1.982
D 4 4 1.976 3.224
P1 5 1 3.082 0.563
P2 5 2 3.082 1.163
P3 5 3 3.082 1.982
P4 5 4 3.082 3.224

TODO

  • Determine mic bias from FTM-300 (I seem to recall it was +4V when I looked on the scope, but need to confirm)