Microwave Journal

A Self-extinguishing Gas Capsule Protector

July 6, 2005

In modern society, electronic systems impact significantly on everyday life, for individuals, commerce, industry and the community as a whole. Their safe and reliable operation is generally taken for granted, as is the humble surge protector that plays such a vital role in maintaining transceiver structures and ensuring the continued functioning of systems. However, the surge protector need be humble no longer as its development enters a new dimension with the introduction of Huber + Suhner’s self-extinguishing protector concept SEMPER to its comprehensive range of lightning gas capsule and surge protectors.

gas Capsule Principle

To fully understand the unique importance of this new development consider the gas capsule lightning protector based on the spark gap principle. This method is probably the most widely used in the protection of electronic circuitry against the effects of surge energy that can damage components by exposing them to overvoltage or excessive heating. For many years they have exhibited a high level of reliability when used as overvoltage protective devices.

The main benefits of the standard gas capsule lightning protector — which acts as a low capacitance switch — is its broadband performance (typically from DC to 2.5 GHz), enabling the device to operate at HF, VHF, UHF and cellular frequencies. In addition, as the units make no electrical contact between the inner and outer conductor of the coaxial line, systems using line power for masthead or remote electronics may be accommodated. The level of residual pulse found with these devices plus the ability to withstand multiple strikes at 20 kA (30 kA single strike) makes them an ideal coarse protection device. They can be selected to match specific system requirements and therefore provide versatility to designers.

As with all engineering solutions, however, the ideal solution rarely exists in practice and the drawback with gas capsule lightning protectors is that when an energy surge reaches a gas capsule device, it arcs over once the appropriate spark-over voltage is reached. The arc initiates a short circuit path from the inner to the outer conductor (earth) and the energy within the surge pulse is diverted to ground. During this time the Tx/Rx system will be inoperative and will only come back on line when the surge pulse has passed and the capsule returns to its non-activated state.

However, while the capsule is activated the short circuit arc can be sustained by relatively low levels of voltage or current as may be found in line power situations or certain RF transmit power scenarios such as CW power or high pulse power with a very high pulse repetition rate. These characteristics can lead to the gas capsule being ‘held on’ in its active state rendering the transceiver system inoperative and leading to equipment damage and destruction of the gas capsule due to overheating.

The SEMPER self-extinguishing protector concept, shown in Figure 1, addresses these problems and drives forward the development of gas capsule protectors. Its self-extinguishing operation enables automatic recovery and extinguishes under any coaxial line condition like malfunction of electronic fused DC supplies and malfunction of RF line monitoring. The new capsule unit, shown in Figure 2 alongside a previous version, is available in a range of configurations, including both complete coaxial protectors and a capsule plus holder subassembly, which can be employed for retrofitting for any of the company’s gas capsule protectors with exchangeable gas capsule. Cost saving is another important feature as the facility for field replacement enables cost-effective system upgrades, while broadband operation, negligible system downtime and higher safety underscore the benefits.

Fig. 1 The SEMPER self-extenguishing protector.

Fig. 2 The new self-extinguishing gas capsule (gold) shown alongside a previous version.

Technical Specifications

The SEMPER concept exhibits impressive operating characteristics too, such as a typical turn-off extinguishing time of 20 seconds at 25?C ambient temperature and 2.0 A DC supply current (see Figure 3) as well as a typical recovery time of seven seconds at 25?C ambient temperature (see Figure 4).

Fig. 3 TSEMPER turn-off time performance

Fig. 4 SEMPER recovery performance

SEMPER works under RF and DC conditions in broad and single band units in the frequency range of DC to 2.5 GHz and is also available as a low intermodulation product, typically –150 dBc with a high RF – CW/average and peak power. It has been developed for voltages up to 48 V and power supply short circuit currents up to 2.5 A, as well as for working temperatures from –40? to +85?C (lightning protection functionality) or from –20? to +85?C (SEMPER functionality). Also, the retrofitting of existing Huber + Suhner protectors with the new capsule unit is possible.

Wide-ranging applications

With complete unit device and replaceable capsule unit self-extinguishing protector options, lightning protection solutions are available for a very wide range of both civil and military applications and system upgrades. In addition, whereas many applications generally benefit from the enhanced safety and reliability that the SEMPER concept offers, those using DC line power for remote signal amplification and processing and those using high RF power are particularly suitable. Specific applications of note include:

  • Feeding DC over coax
  • Transmitting high RF power
  • Tower mount amplifiers/repeaters
  • GPS timing receivers
  • Point to point/multi-point radios
  • Defense/security radios
  • Remote installations


Driven by the strategic, safety and commercial pressures applied by system users on the system providers, demand dictates that efficient, cost-effective system surge protection solutions are available to all design engineers/decision makers working with RF transceiver structures. SEMPER, the world’s first self-extinguishing gas capsule protector and available as a complete device or as a replaceable capsule unit, meets these requirements. It offers a cost-effective and versatile solution for a wide range of civil and military applications, along with system upgrades.

Huber + Suhner,
Herisau, Switzerland,
+41 71 353 4111,