The M-90D and M-90MS utilizes a dynamic microphone element that is finely tuned to deliver rich low to mid frequency response desirable for a clear and concise conversation. 

Using a windscreen cover and a directional micophone element, the structure of the microphone of the M-90D and M- 90MS is designed to concentrate voice input from the front while reducing ambient noise from the side.

Built-in Low-Cut filter creates clear and crisp audio characteristics by shaping the low frequency response (cut off at 340Hz, -6dB/octave). 

An isolation transformer is integrated in the circuit board in order to enhance the audio quality.

The M-90D and M-90MS* are compatible with all YAESU HF transceivers equipped with the round 8-pin microphone connector or the 8-pin modular microphone connector. 

The PTT of the M-90D uses three Air-Cylinder tubes similar to the Reference Microphone M-1. This provides solid and smooth extended operation.  A simple one-touch PTT keylock button is placed directly above the PTT key for those long rag chews.