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Passive Shelter Antenna for Civil Defence Shelters and Protected Facilities: A Passive Communication Solution for Emergency Connectivity

  • Writer: Stanislav Azarov
    Stanislav Azarov
  • 1 day ago
  • 4 min read



Reliable communication is one of the essential operational requirements for civil defence shelters and hardened facilities. Reinforced concrete structures, underground construction, and metallic barriers significantly attenuate radio frequency signals, making conventional mobile communications unreliable inside protected spaces. The Passive Shelter Antenna developed by Atmas Group is designed to enable communication between the interior of a shelter and the outside environment without requiring an external power source.

This article is based exclusively on the information published by Atmas Group in its official product documentation and product webpage.


Introduction

Communication with rescue authorities and external emergency services is a critical component of modern civil defence infrastructure. During sheltering situations, conventional mobile signals are often blocked by reinforced concrete walls and steel structures.

According to Atmas Group, the Passive Shelter Antenna (also referred to as a passive repeater) was specifically developed to maintain emergency communication between people inside civil defence shelters and the outside world.


Operating Principle

The Passive Shelter Antenna is a passive communication device that reproduces radio signals without using its own electrical power source.

According to the manufacturer, the system:

  • receives signals from outside the shelter;

  • transfers those signals inside the protected structure;

  • transmits signals from inside the shelter back outside.

This allows radio and mobile phone signals to pass through reinforced concrete walls and metal structures that would otherwise significantly reduce signal strength.


System Configuration

The communication system consists of two antennas:

  • an outdoor antenna;

  • an indoor antenna.

These antennas are connected by a cable that does not require any external electrical power for operation.

The manufacturer also states that the system enables:

  • mobile phone communication;

  • radio signal transmission;

  • mobile internet connectivity.

Applications using mobile data, including WhatsApp and FaceTime, are also supported according to the product documentation.


Purpose in Civil Defence Shelters

According to Atmas Group, communication with the outside world is one of the key considerations during the design and construction of civil defence shelters.

The Passive Shelter Antenna is intended to provide signal transmission through concrete and metal structures while occupants remain inside the shelter.


Power Independence

One of the primary characteristics of the system is its passive operation.

The manufacturer specifies that the antenna:

  • requires no electrical power source;

  • operates without connection to the electrical grid;

  • can continue functioning when external power is unavailable.

This characteristic makes the system suitable for emergency situations involving power outages.


Testing and Certification

The product documentation states that the Passive Shelter Antenna has undergone multiple tests, including shock and vibration testing.

These tests simulate vibrations generated by external explosions that are transmitted through reinforced concrete structures to equipment installed within shelters. According to the manufacturer, the purpose of these tests is to ensure that civil protection equipment continues functioning during crisis situations.

The official product page additionally states that the device has certification related to use in Finnish civil defence shelters.


Emergency Communication Capabilities

According to Atmas Group, the passive repeater provides communication coverage for civil defence shelters during emergency situations.

The manufacturer states that the system allows occupants to:

  • maintain contact with rescue authorities;

  • receive emergency instructions;

  • exchange emergency messages;

  • remain informed about shelter operating modes, including filtration, blocking and bypass situations.


Installation Requirements

The official installation guidance recommends the following:

  • the indoor antenna should be securely mounted to withstand vibration loading;

  • the outdoor antenna should be installed at a minimum height of 5 metres;

  • indoor cabling should be routed inside a metal conduit;

  • certified fasteners should be used;

  • external cabling should be installed inside a durable protective conduit;

  • the passive antenna system operates when the shelter is in its closed operational mode with doors, hatches and flaps closed.


Installation Method

According to the manufacturer:

  • antenna connections are protected using vulcanized tape;

  • additional shrink sleeves provide environmental protection;

  • the outdoor installation is designed to visually integrate into the building façade;

  • the outdoor installation pipe may be painted to match the building upon customer request.


Technical Specifications

The published specifications for the VSS-5G-SAS-1-SMAN indoor unit include:

Parameter

Specification

Gain

>6 dBi / >9 dBi / 6 dBi

VSWR

≤2.0

Polarization

65°

Vertical Beamwidth

55°

Input Impedance

50 Ω

Maximum Power

100 W

Lightning Protection

DC Ground

Connector

SMA Female (1 m cable)

Mounting

Wall Mount

Dimensions

165 × 155 × 50 mm

Weight

0.3 kg

Reflector Material

Copper

Radome Material

ABS

Radome Colour

White

Relative Humidity

Up to 100%

Operating Temperature

−40°C to +60°C

The manufacturer notes that these specifications apply only to the indoor antenna. An external antenna and connecting cable are required for complete system operation.


Applications

According to the official documentation, the Passive Shelter Antenna is intended for:

  • civil defence shelters;

  • hardened facilities;

  • underground protected spaces;

  • other installations where reinforced concrete and metallic structures interfere with radio signal propagation.


Conclusion

The Passive Shelter Antenna is a dedicated passive communication solution developed for civil defence shelters and protected facilities. According to Atmas Group, the system operates without an external power supply while enabling mobile and radio signal transmission through reinforced concrete and steel structures. The documentation further states that the equipment has undergone shock and vibration testing, supports emergency communication with rescue authorities, and is intended to maintain communication capabilities during shelter operations.


 
 
 

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