Homemade conversion cable to use a desktop microphone on the IC-705
Icom IC-705 desk microphone. How to operate the IC-705 with a desktop microphone
Microphone Jack of the IC-705
4-pin plug is used for the IC-705 microphone jack, as shown below.
The IC-705 Microphone Jack Pin Assignment

The HM-234 plug has 4 pins. However, the regular 3-pin plug can also be used with a speaker microphone that has no key output function. I confirmed that the similar speaker microphone that is used with the ID-51 and ID-31 can also be used with the IC-705.
MIC conversion cable for the IC-705
Components needed
・8-Pin metal microphone jack for desktop microphone.
・Φ2.5mm 4-pole plug
・Cable (2-wire or 3-wire shield)
・Resistor (1kΩ×1、3.3KΩ×1)
・Capacitor (1µF×1)
Wiring
Moreover, when connecting a microphone other than the standard HM-243, UP/DN keys on the connected MIC cannot be used.
You can buy the necessary parts here:
3 or 4 Core Audio Extension Cable Aux Single Head Line 3.5mm
To use an Icom desktop microphone, it is necessary to switch「MIC terminal 8V output」 to 「ON」in the IC-705 Set menu.
For firmware version 1.2 Push [MENU], then touch [SET] > [Connectors ]> [MIC Jack 8V output]→「ON」.
There are various microphones can be used with the IC-705 these days. I realized that there are many types of microphone can also be connecting with the IC-705 and works effectively, it will be interesting to check the sound quality changes by using a variety of microphones with the IC-705.
More: You can directly connect the BM-800 microphone to the icom
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