Sira Radio Systems

Mendip Wraparound UHF Antenna System

Wraparound UHF antenna systems, year 2017

Unique antenna, custom design for the 700MHz clearance project, Arqiva, UK.

Suitable to be mounted around towers with large cross section

Omnidirectional or directional patterns with ripple < 1dB up to 700MHz and < 3dB up to 790MHz

Horizontal polarization

High power handling capability.

Multi-tier solution with high gain.

The request

The 700 MHz clearance programme poses a challenge in terms of masts and antennas that cannot be solved with “standard” wrap around designs, being these antennas narrow banded, thus inadequate as to performances in dealing with both pre-clearance and post-clearance channels.

No need to say that also temporary masts are not the ideal solution because of high implementation cost and long time to deploy.    

The birth of the ‘broadband’ antenna idea

To overcome this situation, our engineers started to consider ways whether a non-banded or ‘broadband’ antenna could be designed to alleviate this situation. The installation of such an antenna would allow both pre- and post-Clearance channels to be accommodated. This would also make it possible to avoid loss of antenna redundancy (except during the relatively short period of each antenna installation) and, most significantly, reduce the requirement for temporary masts. This type of solution would significantly minimise the scope and complexity of the programme and increase the likelihood of achieving Clearance by May 2020.

Our engineers first discussed the concept of Broadband antennas with potential suppliers at the International Broadcasting Convention in 2015. The initial reaction was as expected; limitations of panel technology and physics was cited as the reason why an antenna with acceptable performance over the entire channel range (21 -60) could not be achieved. At that time, it seemed that either compromised antenna resilience or a significant number of temporary masts were inevitable. However, the idea was not dead. Our antenna suppliers started to develop ideas and soon realised the difficulty of the task – particularly because the time did not seem to be available to try, test and develop a product that could be deployed to meet the timescale requirements of the 700MHz Clearance Programme.

After eliminating several potential solutions, Sira came up with the seed of an idea which might just solve the problem. They worked with the University of Milan to develop an Innovative Broadband antenna solution with theoretically astounding performance.

A prototype was constructed and range tested at the Sira facility near Milan and the measured results perfectly matched the theoretical analysis – the Broadband antenna had become a reality.

An Arqiva inspired innovative solution

This innovation has significantly changed the scope and complexity of the 700MHz Clearance Programme. The advent of the broadband antenna allows support of both pre- and post-clearance transmissions on a single antenna and avoids prolonged periods of compromised antenna resilience, minimising risk to DTT services and reducing the requirement for temporary masts.
The first Sira Broadband antenna has recently been successfully put into operation at Mendip and Alan Dick, Kathrein and RFS have also now developed their own products. We’re proud to have inspired this innovation, and grateful to our suppliers who have helped advanced antenna technology which, in turn, has significantly simplified the 700MHz Clearance Programme. As we enter an important stage of the project, we will continue to look at and develop innovative solutions to aid the successful delivery of this critical national infrastructure programme.