Bulletin: SM6140 Vendor: ICOM / IC-2410 Subject: Low Microphone Audio To anyone experiencing low audio with the ICOM 2410A/H, I have just recently purchased one of these myself and ran into the same exact problem. After looking the unit over and determining the same thing regarding an external mic and after a couple of calls to ICOM, we determined the following things need to be looked at: 1. Is the microphone an HM-56 or an HM-56A? If it's an HM-56, then the 4 volt zener should be replaced with a 9.1 volt zener. If it is an HM-56A, no change in the zener is required. 2. If the problem still persists after changing the diode, or if you have an HM-56A, I would recommend replaSing the microphone element with a Radio Shack (NO, I AM NOT KIDDING!!) Part No. 270-090 as the element that came with the ICOM does not have the frequency response characteristics required to produce the low end sounds that make up most of the volume. AfterÓreplacing that element, then touch up on the deviation controls R-5 and R-7 may be required. NOTE: The original microphone element in the ICOM mic has the outer body connected to the positive side of the circuit. The Radio Shack element has the outer body connected to the negative side of the circuit. Therefore, wire the element into the circuit accordingly. I hope this helps out - it has done a terrific job for me. The ICOM now sounds simply marvellous! (Say this line like Billy Crystal!) Thanks to Gary (KF7XV) and LynDel (AA7DG) at ICOM Tech Support for their excellent product knowledgeand technical expertise. Please note that this change is not recommended or supported by ICOM at this time. 73! Brett N9LOU