Futaba sais don't turn on Tx with antenna collapsed?!?
Here's a snippet from their website under the 9C FAQ section:
When I am using my radio for programming, setup within my house, experimenting, etc, is there anything special I should do?
You should ALWAYS extend your antenna at least the bottom or first segment when turning the radio on with a module in place. If left in the radio with the radio on at your work area with the antenna collapsed for more than short intervals, the module will be unnecessarily exposed and may shorten the life or even immediately damage the module/transmitter.
I've always kept my antenna down on my other radios, but then again that may by why my Radiant 6P died and I'm now the owner of a 9C. Is there any real-world experience of damage from this?