Well, better late than never, right? I finally got around to playing
with this and what I said was wrong, Ron was closer to right (although
he may well be correct for the IC-A5, I have an IC-A24). Here's what
I found:

- The PTT switch on the radio only opens the built-in mic on the radio
- The external PTT switch only opens the external (headset) mic.

Pretty simple, right? I was initially fooled into thinking my headset
mic was live when pressing the radio PTT switch when it was actually
the radio mic picking up my voice. This time I was a bit more
rigorous about my experiments and also used an external PTT.

So, you do pretty much need an external PTT if you're planning to use
a headset... why don't they just include it?

todd.

PS: while my plane was in getting some avionics work done I had them
install a connector to let me hook the handheld up to the external
antenna... looking forward to doing some comparisons vs. the whip
antenna.

On Mar 6, 4:02 pm, "tjd" wrote:
On Mar 6, 2:10 am, Ron Wanttaja wrote:

Hmmmm. I was fiddling with an ICOM IC-A5 a while back. I found that when you
used the radio-mounted PTT switch, *both* microphones were live...the one in the
headset, and the one on the radio itself. With the external PTT switch, only
the headset microphone was live.

that's an interesting point, I didn't check that in my test, but
opening both mics would make it a lot harder to xmit cleanly. I will
give it a try when I get home, plus it looks trivial to make your own
external PTT switch so I'll try that too.