I discovered this with my 910H. If you compare the schematic with an older Icom transceiver, say the IC-756, you will notice that the voltage divider on pin 8 decreases the audio on that pin by a factor of about 50 from the IC-756!
I thought of two "cures":
1. Modify the radio by replacing the offending resistor. 2. Modify my headset by bringing the line that would go to pin 8 outside the mic connector and run it to a 1/4" phone plug.
I chose 2. I plug the phone plug into the nearby headphone jack when I use the headset, or pull it out to use the speaker. Works on both my 910 and 756.
I was told by a person at Heil that Icom made that change to better use a TNC with the mic connector on the 910.
Ron W5RKN
Date: Tue, 9 Jun 2009 05:21:35 +0300 From: Kostas Ioannidis kostas.ioannidis@gmail.com Subject: [amsat-bb] IC-910H low audio problem. To: AMSAT-BB@amsat.org Message-ID: 6cd5903a0906081921k5cb111e0j945fc7b09e7d040@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1
According to the IC-910H manual, pin number 8 at the mic connector is audio output (which varies according to af control). I connected a pair of headphones at the pin but the audio is way to low and cannot be used for listening. Is it normal? I thought that it was designed for this purpose. Am I missing something in the menus? Thanks in advance!
73 de SW1IXP, Kostas Ioannidis