I tend to pull the battery and leave the crystal and antenna in the TX that will be the buddy box.... except with JR (I think airtronics is same as JR here.. haven't delt with theirs..) then you pull the crystal.

Leave the antenna alone unless you are dedicating an old TX to permanent buddy box service. Removing the antenna can loosen up a screw inside that is impossible to check on without pulling the TX back. If that screw comes out... the antenna will be disconnected from the transmitter. Plus... the screw can drop onto the TX circuit board and short it out. (maybe destroying the TX...)

If you have the habit of unscrewing the antenna from your TX... you need to periodically check inside to see if the screw that retains the wire connection to the antenna is tight.

(typing too fast... )