(Ben Jackson) wrote in message news:KBvDb.553661$HS4.4223865@attbi_s01...
Somewhere I read that you should NOT acknowledge transmissions by just
pressing PTT briefly. Now, I had never heard that before, nor done it,
but since then I think I've heard it happen.

Can someone who is familiar with this explain the PTT-ack customs so I
know how to interpret it?

A lot of pilots use the double-click of the PTT as an acknowledgement
to a transmission that didn't need to be acknowledged. It is
primarily used as a courtesy to the controller to let them know that
you heard their last transmission - even if a reply wasn't required.

An example: Leaving Class D airspace.
Cherokee 62R: Tower, Cherokee 62R is clear to the North, have a good
afternoon.
Tower: 62R, freq change approved, have a good afternoon too.
Cherokee 62R: key the mike twice.

The key is (pun intended) - there are not many situations where the
double-click is acceptable. Unfortunately, many pilots key the mike
(or use Roger/Wilco), when a proper reply was required. Ie taxi
instructions, hold-short, etc.

-Nathan