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Non-Intrusive Radio System for a London Council

Due to OFCOM licensing pressures in London, the Council system had to be engineered in such a way as to cover the building of 8 floors, whilst at the same time minimising radiation outside of the building. Consam therefore were asked to develop and implement a distributed antenna system in order to cover the 8 floors including an underground swimming pool,

A major concern was tailoring the radio propagation of the system to cover the 8 floors of the building whilst minimising the collateral radio radiation to ensure that the system did not travel over any unnecessary distances outside the building, as the frequency was reused by the Council less than 1KM away

Initial testing with a roof mounted down fire antenna proved unsuccessful for 2 reasons, firstly it was not possible to cover the basement area from the roof antenna location and secondly the roof mounted antenna transmitted over much too wide an area, which potentially would have caused interference with the customers other system. Due to the dome glass roof of the building it was impossible to site a centrally mounted down fire antenna, the available positions resulted in poor coverage down the extremes of the building.

Consam tried externally mounted antennas on each corner of the building, but this only resulted in skewed coverage with areas of poor or no coverage in the opposite stairwell areas, and due to cosmetic pressures, we could not use visible antennas in the atrium area of the building.

However, we had found that by using multiple linked antennas in the atrium area we could cover the building from top to bottom whilst limiting radio propagation outside of the building.

Due to cosmetic limitations we had to source the most discrete indoor antennas that would provide the required coverage pattern. The main challenge was linking multiply antennas together in a modern building without leaving any visible cables.

By working in close partnership with the construction company and facilities management team we were able to utilise the buildings dry riser IT network connections. This allowed us to mount the Hytera transmitter high up in a building with antennas mounted discretely on flat walls, and were distributed around the building by using the network dry risers, thus ensuring radio coverage throughout the building whilst not impinging on the cosmetic regulations of the brand-new building.

The customers full radio coverage had now been achieved without being visible to radio users (i.e. no obviously visible antennas).

In addition, by the use of multiple indoor short range hidden antennas, we have also achieved the OFCOM requirement that the system does not radiate more than a few metres outside the building and thus does not interfere with the customers other radio system on the same frequency approx.. 800 meters away

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