Dual Insert Microphone for Icom IC-7300 Transceiver

This resource details the construction of a dual insert microphone specifically designed for the Icom IC-7300 Transceiver. The microphone utilizes a Besson BZ2400 M4 Rocking Armature insert for frequencies from 500 Hz to 3 kHz, providing a rising response of approximately 11 dB. A generic Electret Condenser insert, powered by the transceiver's microphone line, covers the low-frequency range from 100 Hz to 500 Hz. A Low Pass Filter is incorporated after the Electret insert to prevent frequency overlap. A pre-set potentiometer (VR1) adjusts the low-frequency response, balancing the output of both inserts. The design emphasizes a "Close Talking" arrangement and addresses audio "colorization" by housing the Besson insert in a thick rubber holder with a foam boot, separate from the circuitry. The Electret insert is also wrapped in a foam boot. Critical importance is placed on using the correct BZ2400 M4 insert with 12 holes in its face plate.