Can the FT-817 Yaesu microphone be modified to use the Heil HC-4 and HC-5 inserts?
YES. M0AWS removed the Yaesu microphone insert, modified the TONE switch on the back, and connected the HC-4 and HC-5 inserts instead of the discrete components. Then with a flick of the switch, you have either HC-4 or HC-5 insert ready to use! For information on this modification, see his web site http://www.cybatek.fsnet.co.uk/m0aws/FT817-mic-mod.html. The photographs and discussion should help you accomplish this modification easily.