29 Mar IC-705 8 pin mic adapter
Last Updated on September 5, 2022
Build an 8 pin mic adapter for your IC-705
An IC-705 8 pin mic adapter can be built for under $15. The Icom IC-705 is an amazing radio. It’s perfect for everything from DC to daylight. The microphone that’s supplied with the radio – the MH-243 works, but what if you need or want to use a different microphone? A recent search on the internet found many aftermarket adapters and converters, but one result had a circuit diagram. So rather than spend $40 USD and wait weeks for delivery it was time for a trip to the local Jaycar to grab some bits to make my own.
I use my IC-705 as an IF radio for microwave and could really use a ‘K’ generator to signal the end of transmission for weak signal 10 GHz QSOs. The 8 pin option was the best suited to solve this problem.
There is a caveat on this circuit… It works perfectly when the power to the radio is an external source. When the radio is running on its internal battery, the audio wasn’t as good and there was unidentifiable background noise. My test was with two microphones, the SM-30 desk mic and an HM-219 handheld mic. This generic mic is supplied with many Icom transceivers these days such as the IC-9700 and IC-7300.
When connecting a microphone other than the standard HM-243, the UP/DN keys on the connected mic cannot be used.