Electret Microphone Adapter for Yaesu MH-31

Electret Microphone Adapter for Yaesu MH-31 (FT-991A & Others)

This is a custom-designed internal adapter for the popular Yaesu MH-31 hand microphone. It allows you to easily replace the stock dynamic element with a high-quality electret condenser microphone, significantly improving your transmit audio clarity on radios like the Yaesu FT-991A, FT-817/818, FT-857, and FT-897.

Technical Specifications

• External Diameter: 31.6mm (perfect friction fit for the MH-31 housing).
• Internal Bore: 9.6mm (designed for standard electret capsules).
• Material: Optimized for TPU or flexible filaments to provide vibration isolation and a snug, rattle-free fit.

Features

• Drop-in Replacement: Designed to sit perfectly within the original microphone casing without permanent modifications.
• Improved Audio: Switching to an electret element provides a brighter, more "punchy" audio profile, often preferred for DX and clear communication.
• Universal Compatibility: While designed for the MH-31 used with the FT-991A, this adapter works for any Yaesu radio using the MH-31 microphone series.

Printing Tips

• Filament: TPU (95A or softer).
• Infill: 15–20% for a good balance of flexibility and structural support.
• Supports: No supports required.

Important Note

• I am providing the 3D-printable adapter only. Converting from a dynamic to an electret microphone requires a simple electronic circuit (resistors/capacitors) to provide bias voltage. Detailed wiring diagrams and conversion guides for this popular modification are widely available on the internet (search for "MH-31 electret mod").