Marker - 900 mm. Metal aircraft use the airframe for this purpose but wooden or glass fibre structures require a purpose made device. This could be a suitable sized aluminum doubler plate or even some metallic foil. All ground planes must be connected by some effective means to the screening of the feeder cable. They should also be either well insulated from the airframe or efficiently electrically bonded to any metal in the vicinity.
Dipole antennas require no ground plane.
This can consist of electronic circuitry, ferrite torroids or, as described later, made from the feeder cable. RG58U. This cable is of the coax type and has an impedance of 50 Ohms, a stranded conductor and the insulation is non-contaminating. A stranded conductor is more flexible and less susceptible to breakage than a solid conductor. These features far outweigh the slight decrease in signal strength. Cheaper cable should not be used, as the quality of the screen is usually the first to suffer.