IW7EHC Web Site

ICOM RADIOS MICROPHONE ADAPTER

Few weeks after I published this website,I received an interesting email from Federico IW1QN ( www.acehighdx.org )

He sent me the schematic of an adapter for the ICOM radios,to interface them with pc or communications headsets.

A feature of the ICOM radios is the phantom power supply to the microphone:

on the mic audio wire it's available a DC voltage (8 V),used to power up the amplified cartridge,provided in the stock mic.

As shown in the schematic of the ICOM HM-36 microphone,from the mic AF wire there are 2 links to the cartridge:

through the 2Kohm resistor the 8 V dc are reduced to 2 V,the proper voltage level required to power the element.

Through the 0,33 microF capacitor the AF signal from the mic is sent to the radio.

This capacitor is required to decouple the AF side from the DC voltage available on the same bus.

The remaining 3 capacitors are required to "drain" stray RFI to ground.

A simple universal adapter can be made,by keeping the same configuration,and replacing the mic element with the proper socket.

It will be possible to plug in any kind of amplified microphone,customizing the wiring to the socket,if required.