Lightning protection for amateur radio systems

Most radio amateurs probably don't realise the consequences of a lightning strike on their antenna system. Are the measures taken sufficient?

If you look at normal residential buildings and take into account that lightning strikes preferentially into metal structures that protrude above the roof, such as antenna systems, you can say that the antenna earthing of roof antennas is de facto a "mini lightning protection" for the shack. This is an additional motivation for earthing a roof antenna.

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FAQ

Why do I need lightning protection for my antenna?
Lightning protection is necessary to protect your antenna from the harmful effects of lightning. This can help prevent damaged equipment and losses of data or signals.
How do I install lightning protection for my antenna?
The installation of lightning protection for your antenna should be done professionally. The lightning protection will be connected directly to the antenna input and grounded to ensure protection.
What type of lightning protection is best suited for my antenna?
The type of lightning protection that is best suited for your antenna depends on various factors such as the type and size of the antenna, reception area, and local weather conditions.
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The standard DIN 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The following explanations are based on the current, as yet unpublished draft standard, which is expected to be published in 2024.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

  • 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.

  • 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.

  • 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.

  • 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.

  • 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:

  • 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.

  • 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.

  • 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

  1. Use of lightning current carrying antennas - uncommon in amateur radio
  2. Installation of antennas in areas protected from lightning strikes - possible for local radio, relay connections or QO100 antennas (figure)
  3. 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.

  1. at the antenna mounting
  2. where the antenna cables enter the shack building
  3. in the shack
  4. for free-standing antenna masts and long cables at the base of the mast
    1. These additional potential equalisation rails are connected to the main earthing rail.

Potential equalisation in the shack

Fig. 7: Potential equalisation in the shack / DARC AK antenna earthing

Shack buildings: Optimum lightning protection system

Fig. 9: Components of a lightning protection system according to VDE 0185-305-3 / VDE

Use cases

1 lightning protection system required by the authorities, free-standing antenna mast
Antenna mast
Antenna earthing + potential equalisation
Shack building
  • Potential equalisation with SPDs*
  • Only by a lightning protection specialist
2 lightning protection system required by the authorities, e.g. high-rise building
Worst case: only by a lightning protection specialist
Antennenmast
Protect aerials from lightning strikes using air-termination rods
Shack building
  • Use insulated down conductors if necessary
  • Temporary installation of antenna systems
3lightning protection system installed voluntarily, radio amateur as sole user
Is a reduction in the protective effect of the lightning protection accepted? Minimum: Antenna earthing + potential equalisation according to VDE 0855-300
4lightning protection system installed voluntarily, multi-party house
as 3., coordinate procedure with other parties Tip: Involve a lightning protection specialist

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:

  1. Do direct or indirect lightning currents occur? → Current 10/350 µs or 8/20 µs relevant
  2. How high is the estimated lightning current at this point?
  3. What is the maximum rated current or rated power?
  4. What is the maximum operating voltage?
  5. What connections (plug/socket) must the surge protective device have?
  6. 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:

  1. Building earth electrode, e.g. via an existing connection lug on the outer wall
  2. Main earthing busbar, to which the building earth electrode is connected
  3. 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.

Important standards for antenna earthing and lightning protection

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

Further information, literature

Baumanns, H.: Der falsch verstandene Überspannungsschutz. Funkamateur 10/2009, Box73 Amateurfunkservice

Bissinger, N.: Schutzmaßnahmen verstehen und anwenden. cq DL 8/2017, DARC-Verlag

Blauermel, R.: Blitzschutz für Antennenanlagen. Funkamateur 7/2019, Box73 Amateurfunkservice

Block, R.: Lightning Protection and Grounding Project at W2MMD. QST 7/2022

Ellison, T.: Grounding Systems in the Ham Shack – Paradigms, Facts and Fallacies. https://helpdesk.flexradio.com/hc/en-us/articles/204779159-Grounding-Systems-in-the-Ham-Shack-Paradigms-Facts-and-Fallacies (abgerufen am 20.02.2023)

Friese, W.: Blitze und Gewitter funktechnisch betrachtet (1)+(2). Funkamateur 4+5/2005, Box73 Amateurfunkservice

Hann, W.: Überspannungsschutz bei KW-Antennen. Funkamateur 11/2006, Box73 Amateurfunkservice

Heidler, F.; Stimper, K.: Blitz und Blitzschutz. VDE Schriftenreihe 128. VDE Verlag, 2009

Krischke, A.: Rothammels Antennenbuch, Kapitel 34.3 Blitz- und Erdungsgrundlagen. 13. Auflage, 2014. DARC-Verlag

Lechner, D.: Blitzschlag - sind Sie gerüstet?. Funkamateur 1/1972, Box73 Amateurfunkservice

Maneck, H.-J.: Blitzschutzsystem für die Amateurfunkstation. Funkamateur 3/1996, Box73 Amateurfunkservice

OBO Bettermann: Sicherer Blitz- und Überspannungsschutz (Video) https://www.youtube.com/watch?v=8basjDr0Ik0 (abgerufen 30.05.2023)

Österreichischer Verband für Elektrotechnik: Blitz- und Überspannungsschutz sowie Erdung von Antennen und Antennenanlagen. OVE-Fachinformation BL02. 2021-02-01

Patterson, R.: Lightning in Super Slow Motion (Video) https://www.youtube.com/watch?v=RLWIBrweSU8 (abgerufen 30.05.2023)

Raphael, T.: Blitzschutz und Antennenerdung. Funkamateur 1/2010, Box73 Amateurfunkservice

Roth, W.-D.: Blitzschutz - eine sinnvolle Basis für die Funkanlage. Funkamateur 6/2010, Box73 Amateurfunkservice

Schröder R.; Müller, K.-P.: Blitz-/Überspannungsschutz von Funkanlagen. cq DL 3/1992, DARC-Verlag

Sichla, F.: Blitz- und Überspannungsschutz: Für Antennen, Geräte und Anlagen. vth Verlag, 2011

Sichla, F.: Blitz- und Überspannungsschutz für Amateurfunkanlagen. Funkamateur 7/2009, Box73 Amateurfunkservice

Sichla, F.: Blitzschutz & Co: Funken – aber sicher! cq DL 5/1999, DARC-Verlag

Sichla, F.: Blitzschutz im Shack. cq DL 8/2017, DARC-Verlag

VDE e.V.: Schutz von Funkanlagen auf Gebäuden bei Blitzschlag - Leitfaden für die Anwendung von DIN VDE 0855-300 (Antennenerdung) und DIN EN 62305 (Blitzschutz). VDE Information Blitzschutz. www.vde.com/blitzschutz-funkanlagen (abgerufen am 20.01.2023)