Maxxon HCB-30C El Manual Del Propietario página 13

To convert the HCB-30C portable to a mobile
radio: Disconnect the "Rubber Duck" or telescopic
antenna and connect your vehicle/boat's mobile
CB antenna (or optional magnetic mount antenna
WTA-4W). NOTE: Mobile antennas utilize the
vehicle's metal body as the "ground" plane. When
mounted on the corner of the vehicle, this type of
antenna tends to become slightly directional by the
particular corner it is facing. (This slight directional
characteristic will only occur when transmitting/
receiving over an extreme distance).
10