Antennas with a radiation characteristic of 360° are used in different fields of radio application. Such antennas usually are known as “omnidirectional antennas” (omni antennas). Typical applications of omnidirectional antennas in practice are private mobile radio (PMR) systems, safety nets and sometimes also GSM networks. In GSM networks, however, they are only applied if there is a low frequency of radio waves.

For omnidirectional antennas it has to be taken into account that metal structures in the direct vicinity have a negative, i.e. attenuating influence on the radiation characteristics. Hence, the father from the antenna, the lower the influence of these structures on the radiation characteristics.
Together with the Kathrein company in Rosenheim, Germany, DEHN carried out measurements for evaluating what kind and size of nearby metal structures interfere the radiation characteristics.

When installing an isolated air-termination systems at an omnidirectional antenna it has to be minded that an isolated air-termination rod provides a sufficient protective angle for the antenna to be protected. A sufficient separation distance s has to be kept as well.