Abstract: An antenna-supporting arm is hingedly connected to a small semi-permanently attachable plate to be positioned in the usual rain channel underlying the margin of the hood of the engine compartment (or the lid of the trunk) of a motor vehicle. When the hood or lid is temporarily raised, the supporting arm and the antenna mounted thereon are swingable between an exposed normal use position, and a completely concealed under-cover position for preventing theft or vandalism. A support-grounding pigtail lead bridges the hinge and is electrically connectable to the rain channel by one of the bolts fastening the small plate therein.