Mechanical structure of the antenna
The antenna is housed in a round weatherproof plastic casing. The casing cover is arched to prevent any rain water, snow or other impurities from settling on the antenna.

The mechanical construction consists of sturdy, anodized aluminium or aluminium die-casting and is designed to resist high winds.

The plastic housing can be installed horizontally as well as vertically to the mechanical parts, allowing both wall and flat-roof installation of the antenna. The antenna cable can be fed either through the base or through a slot on the side of the mounting flange.

Electrical structure of the antenna
As the antenna is non-directional, reception cannot be improved by mechanical shaping as, for example, with parabolic antennas. Therefore the signal strength at the antenna input is about 1 x 10-16 Watts and already below the generally permitted noise level.

An extremely low-noise pre-amplifier is placed behind the antenna in order to feed the signals to the electronics via an antenna cable. The antenna cable also supplies the voltage to the pre-amplifier.

When outdoor antennas are used high interference voltage or current pulses may occur in the antenna cable during thunderstorms. This may result in damaging or destroying not only the directly connected radio-controlled clock system but also any other devices connected.

To avoid severe damage and damage-related costs an indirect lightning protection should be installed between the outdoor antenna and the circuit board of the radio-controlled clock.

This is why the hopf lightning strategy is made up of a combination of rough and fine protection.

Rough Lightning Protection
The double-chamber gas arrestor, located in the lightning protection, has a dynamic operating voltage of < 700 V and conducts voltage, when ignited, out of the cable to the earth potential.

Fine protection (in the hopf GPS receiver board)
Fast absorber diodes with a response time of < 1 nsec. and an absorber power of 600 W at the input of the GPS receiver board keep the potential differences between antenna core and zero at a constant approximate ± 6 V until ignition of the double-chamber gas arrestor.

Because of the high frequency and the signals below the permitted noise level, the elements must be set up in strip-line sequence. This combination also guarantees the potential separation of the antenna circuit to other electronics in conditions without interference.

If no further devices (eg. power splitter) are installed between lightning protection and electronic with fine protection, for safety reasons a maximum cable length must not be exceeded (please have a look at the drawings in the technical manual which can be found in the tab 'Download').