I'm not a controller, but I do have a copy of the AIM that says in capital
letters (4-1-18) that you are supposed to have it on at all times, and in
4-1-19 regarding code changes, does not tell you to turn it off.

So the second instructor was right.

Bob Gardner

"Ken Pruchnick" wrote in message
om...
What is the proper way to switch transponder codes? The way I have
been taught is to put the transponder in stand by, switch to the new
code. Then turn it to mode C
I had an instructor tell me to just change it to the new code without
turning it to stand by first.
Like to hear from controllers as to what they prefer.