A terrestrial network is a ground system from many metal strips laid in the ground which serves to low grounding a vertical transmission antenna. This is particularly necessary for T antennas and radiating transmitting masts in the long -, long - and medium-wave band, which in this way the required second dipole half is replaced. The decisive factor is as low as possible grounding resistance of a few ohms, which significantly below the feedpoint impedance of a quarter-wave radiator of only 36 Ω.
Supplied by the transmitter antenna current I oscillates in rhythm with the transmission frequency that is between the ground network and the antenna, and therefore the terrestrial network is also referred to as " counterweight ". The total load resistance of the transmitter is the sum
The respective power calculated to be
If one wants to radiate as much power and the soil heat only slightly, the grounding resistance RErdnetz must be as low as possible.
A terrestrial network comprises a plurality of bands, the length at least of the height of the transmit antenna corresponding to, but usually is one quarter of the wavelength of the radiated frequency. In areas with poor soil conductivity terrestrial networks have also been built, the length times the radiated wavelength exceeds 1.5.
The Erdbänder of galvanized steel are buried at shallow depths (up to 50 centimeters). If a burial in rocky ground impossible, they are possibly installed above ground on small masts. The bands of earth net run radially towards the antenna support. They should not cross each other.
For transmitter systems on ships and marine platforms anchored a good grounding is ensured by the electrically conductive sea water on the hull. In these cases, no extensive ground network is needed.