Yaesu Md 100 Schematic May 2026

Because the DC supply from a radio can be noisy (especially during transmit), the MD-100 includes an RC (resistor-capacitor) filter network and sometimes a Zener diode regulator (e.g., RD5.6EB) to provide a clean, stable voltage to the electret capsule.

Many users modify the MD-100 schematic to improve performance.

Amplifier Bypass: To reduce noise floor, some owners open the unit and bridge the input and output pads of the internal amplifier, turning the unit into a passive microphone (relying solely on the rig's preamp).

This is simpler. The radio provides a stable +5V on Pin 5 (often labeled "Vcc"). Yaesu Md 100 Schematic

  Radio 8-pin
    Pin 5 (+5V) -----> [Direct] ----> Electret Capsule (+)
    Pin 1 (GND) ---------------------> Electret Capsule (-)
    Pin 2 (MIC) <--------------------- [C2 1uF/50V] <--- Audio output
    Pin 3 (PTT) --[ Switch ]--------> GND (Pin 1)
    Pin 4 (UP) ---[ Switch ]--------> GND
    Pin 6 (DOWN) -[ Switch ]--------> GND

Note on A8: No internal regulator. The mic relies entirely on the radio's clean +5V. If you have hum, check the radio's voltage, not the mic.

The MD-100 features a substantial Push-To-Talk (PTT) bar on the base. Because the DC supply from a radio can

Schematic Logic:

Understanding the MD-100 schematic also opens the door to modifications: Amplifier Bypass: To reduce noise floor, some owners

A signature feature of the MD-100 is the three-position toggle switch (often unmarked or labeled 1-2-3) used for frequency response tailoring. This is an RC (Resistor-Capacitor) filter network.

The MD-100 uses a standard 8-pin round connector (often called a "Hirose" or "Yaesu 8-pin"). The schematic labels each pin: