The standard VDE 0800-300 "Radio transmitting/receiving systems for transmitter output powers up to 1 kW - Part 300: Safety requirements", which is relevant for radio amateurs (in buildings without a lightning protection system), is currently being revised in collaboration with some of the authors of this article.
The following explanations are based on the current, as yet unpublished draft standard, which is expected to be published in 2024.
This article introduces the technical and organisational measures for earthing antennas and providing lightning protection for stationary amateur radio stations. Additional overvoltage protection measures are useful if electrical devices in the shack and possibly in the shack building are to be protected.
Terms
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Radio installation (amateur radio station):
A radio installation is the entirety of a permanently installed antenna system, radio equipment, antenna and power cables, power supply, system technology and associated infrastructure.
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Antenna earthing:
Electrical connection of an antenna system to an earthing system so that the lightning currents occurring in the event of a lightning strike to the antenna system are conducted to earth.
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Potential equalisation:
Establishing electrical connections between conductive parts such as antenna masts, shields of coaxial cables, metal housings of radio equipment in order to achieve potential equalisation. If this is done to protect people, the measures are called protective equipotential bonding.
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Lightning protection, lightning protection system:
Protective measures against the effects of lightning discharges on persons, structures and technical equipment. The coordinated protective measures are called a lightning protection system.
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Surge protection:
Protective measures against the effects of overvoltages. This includes the use of surge protection devices or the shielding of devices and cables.
Important statements can already be derived from these definitions:
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Antenna earthing:
Antenna earthing is neither lightning protection nor (protective) equipotential bonding, but the discharge of lightning currents from the antenna to earth; this reduces fire and personal injury caused by lightning currents, but damage to property, e.g. electrical appliances, is still likely.
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Potential equalisation:
Potential equalisation reduces contact voltage and is therefore the most important measure for personal protection; damage to property, e.g. electrical appliances, is nevertheless likely.
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Surge protection:
Surge protection protects appliances + technology; technically speaking, potential equalisation is created for active conductors with surge protection devices.
Note
This article contains general technical information on aerial earthing and lightning protection. It is therefore always essential for the person using the equipment to check the required course of action. The authors have taken great care in compiling this information. Nevertheless, they cannot assume any explicit or implicit guarantee for the correctness, completeness or up-to-dateness of the document. It is used in the knowledge that the authors cannot be held liable for damages or losses of any kind.
Lightning protection does not require legal advice. Experts are needed here!
Lightning conductor for antennas: Safety through earthing
Important note:This text only applies to buildings without a lightning protection system. If you operate a radio system in a building with a lightning protection system, see Part 3.
Amateur radio antennas are often installed above building roofs and are therefore favoured lightning strike points. The antenna system must therefore be constructed in such a way that no additional fire hazard is caused by lightning and no parts can be blown off that could endanger people or property.
Fig. 2: Antenna earthing / DARC AK Antenna earthing
Figure 4: Antenna in lightning protected area: (a) air-termination rod, (b) on building wall, (c) outside the building, (d) inside the building / DARC AK Antenna Earthing
Antenna
- Use of lightning current carrying antennas - uncommon in amateur radio
- Installation of antennas in areas protected from lightning strikes - possible for local radio, relay connections or QO100 antennas (figure)
- Permitting lightning strikes in antennas with acceptable material damage
The last approach will be the most common in amateur radio. This results in flashovers between antennas and the nearest earthed parts, usually the antenna cable and the antenna mast. Caution: Reduce the risk of fire by removing flammable material!
Earthing conductor
The earthing conductor establishes an electrically conductive connection between the antennas and an earthing system. A copper conductor with a cross-section of at least 16 mm² is usually used for this purpose. If possible, it should be routed outside the building along the shortest route from the antenna mast to the earthing system.
Earthing system
In the simplest case, the building earthing system is used. For further information, see Part 5.
Fig. 5: Potential equalisation with surge protection devices for coaxial antenna cables / DF4KJ
Focus on potential equalisation: Understanding protective measures
"Potential equalisation" is the most important measure for protecting people and technology: everything metal is connected directly or indirectly to each other and, if necessary, to earth (the earth potential, the "remote earth") via conductors or surge protective devices. For personal protection, everything metal that can be touched with outstretched arms and can carry different potentials is considered.
Equipotential bonding conductor= copper conductor with a cross-section of at least 4 mm² (for protected installation, e.g. in a cable conduit 2.5 mm²), for conductors between equipotential bonding bars and the main earthing bar 6 mm².
Fig. 6: Potential equalisation at several points / DARC AK antenna earthing
Due to the high lightning currents, equipotential bonding on the main earthing busbar (in the basement) is not sufficient! For this reason, additional local potential equalisation (figure) must be carried out, e.g.
- at the antenna mounting
- where the antenna cables enter the shack building
- in the shack
- for free-standing antenna masts and long cables at the base of the mast
These additional potential equalisation rails are connected to the main earthing rail.
Potential equalisation in the shack
Shack buildings: Optimum lightning protection system
Fig. 9: Components of a lightning protection system according to VDE 0185-305-3 / VDE
Use cases
- Potential equalisation with SPDs*
- Only by a lightning protection specialist
- Use insulated down conductors if necessary
- Temporary installation of antenna systems
For further general information on lightning protection, see e.g. VDE e.V. :
*SPD = surge protection device
Surge protection: Protect radio technology
Fig. 10: Surge protection devices for coaxial antenna cables at the base of the mast / DF4KJ
Surge Protective Devices (SPD) must be selected and installed appropriately for the respective application:
- Do direct or indirect lightning currents occur? → Current 10/350 µs or 8/20 µs relevant
- How high is the estimated lightning current at this point?
- What is the maximum rated current or rated power?
- What is the maximum operating voltage?
- What connections (plug/socket) must the surge protective device have?
- What is the maximum permissible overvoltage (dielectric strength)?
SPDs type 1 / D1 = lightning current arresters:
discharge lightning currents to earth / protective conductor; the response voltage is relatively high; observe the maximum surge current (10/350 µs or 8/20 µs) according to the data sheet
SPDs type 2 / D2 = surge arresters: discharge overvoltages to earth / protective conductor; discharge low lightning currents (8/20 µs) to earth / protective conductor; destruction in the event of higher lightning currents
SPDs type 3 / D3 = surge arresters: with lower response voltages, usually in combination with SPD type 2 / D2
Tip
If an appliance is to be protected, surge protection must be provided for all cables connected to the appliance.
Wichtig
Earthing system: One or more?
In the case of a free-standing antenna mast, a flat bar is usually inserted in the foundation as a foundation earth electrode. This earth electrode is connected to the main earthing bar by means of an equipotential bonding conductor.
For antenna masts on buildings, the earthing conductor is preferably installed on the outside of the building (otherwise inside the building). 3 options for connection to an earthing system:
- Building earth electrode, e.g. via an existing connection lug on the outer wall
- Main earthing busbar, to which the building earth electrode is connected
- Separate earthing system; this is connected to the main earthing rail of the shack building with an equipotential bonding conductor.
Fig. 11: Earthing systems for antenna earthing / DARC AK Antenna earthing
VDE standards:
Why they ensure safety
Fig. 12: Cover sheet of the standard DIN VDE 0855-300:2008 Radio transmitter/receiver systems for transmitter output powers up to 1 kW - Part 300: Safety requirements / DKE
There is no law or regulation stating that antenna earthing is a necessary obligation. However, the principle applies that VDE standards reflect the recognised state of the art. In the event of damage, anyone who deviates from this may have to prove that all necessary and reasonable precautions have been taken to prevent damage to others. This refers to those measures that a prudent and reasonable person would consider necessary and sufficient to protect others from damage (see Wikipedia - Duty to ensure public safety). This is fulfilled if the usual protective measures such as antenna earthing and potential equalisation are implemented. Such a building is basically better protected against the effects of lightning than one without a radio installation.
In recognition of the experimental nature of amateur radio, the VDE 0855-300:2023-xx standard states in section 7 that the protective measures formulated in the standard do not necessarily have to be complied with in full; however, the protective equipotential bonding measures are to be implemented as a priority. This refers to antenna types for which antenna earthing is not possible. Or an antenna that has just been built by the customer is tested in a temporary set-up. Nevertheless, the protection goals - reducing the risk of personal injury and fire after a lightning strike - must be taken into account and alternative measures must be taken. At the very least, this should be considered and documented in writing.
Conclusion:
Antenna earthing in accordance with VDE 0855-300 is - with a few exceptions - not a legal / official obligation, but it is recognised state of the art and must therefore always be applied. Deviations must be well justified and, if possible, documented.
DIN EN 60728-11 (VDE 0855-1):2019-02 Cable networks for television signals, sound signals and interactive services - Part 11: Safety requirements (IEC 60728-11:2016 + COR1:2016); German version EN 60728-11:2017 + A11:2018
DIN VDE 0855-300 (VDE 0855-300):2008-08 Radio transceiver systems for transmitter output power up to 1 kW - Part 300: Safety requirements
DIN EN 62305-3 (VDE 0185-305-3):2011-10 Lightning protection - Part 3: Protection of structures and persons (IEC 62305-3:2010, modified); German version EN 62305-3:201
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