At least Airwave receivers have power on the antenna jack. You have to disable the power feed somehow in order to use "short circuit" antennas like SPW or CL. If you just throw SPW or CL in it shorts out the power coming out from the antenna jack and (presumably) shuts off the receiver.
For one particular Airwave module there's some kind of tutorial on how to disable the power from the antenna jack: http://www.electronicarc.com/catalog...roducts_id=532
The picture is not clear but you have to cut one lead on the circuit board.