Radar Realities

When it comes to protecting radar installations, efficacy should always come before price. Prudent specification can nevertheless ensure that budgets are not disadvantaged. AlanDick advocates a holistic approach.

The growing fear of international terrorism and resulting raised levels of tension have brought an increasing focus on homeland security and the means of advanced warning against airborne threats. With warning radar back under the spotlight, vendors are reporting increased interest from governments as defence priorities are once again redefined.

Even in these troubled times, however, defence procurement departments are subject to the same budget constraints as other purchasers and are under intense pressure to achieve ‘best value’. Fortunately for all concerned, best value considerations mean due regard is now being given to lifetime deployment and support costs, with buyers rating technical effectiveness equally with price.

Although it’s the technical equipment that grabs the headlines where modern radar is concerned, the radomes used to enclose and protect it perform an equally vital role by assuring the availability and longevity of the scanners inside. Because this role is not universally recognised, a temptation arises for cost cutting, which at worst can prejudice the far larger investment made in the installations as a whole. This is why a holistic approach taking all factors into consideration is so necessary.

Hostile environments

Understandably, many otherwise well-informed professionals see radomes as little more than a weatherproof shield against environments that are hostile in terms of temperature and humidity extremes or else by way of harmful salt spray, periodic ice build-up or extreme sandstorms. Other hazards include ultra-violet radiation from the sun, fungal and insect infestation and corrosion. Radomes do indeed protect and extend the service lives of antennas, pedestals and their supporting systems, but not only against the items mentioned. Their other key function is as a windshield, deflecting the gusts that might otherwise blow the motorised scanning antennas off true and cause the gearboxes to fail prematurely. Wind load is thus a key factor for consideration when designing and specifying radomes.

There is also a temptation to assume all radomes are made the same, prompting cost comparison to be made on a simple size and volume basis. In fact radomes can be made from solid laminate, sandwich or foam materials, either pre-impregnated or laminated by hand. Our company happens to use a hand-laminated process, since this is more flexible and allows structures to be built up using a greater number of layers for use in areas of high wind load such as the Falkland Islands. The tooling costs are also lower, making the final price more competitive.

Another factor in which radomes differ is in their transparency to radar signals. The goal of course is to minimise the attenuation or transmission loss caused to the radio frequency (RF) signal passing through the radome wall and mitigate any scattering loss resulting from reflections off the panel flange framework. As noted by many observers, the scattering loss from the framework can be several times greater than the attenuation caused by the radome wall, although this need not be inevitable.

Competing tenders

To determine the most appropriate solution buyers will need to consider separately and in aggregate the RF, electromechanical and structural characteristics of the radome and tower combination, with a good understanding of each of the sciences involved. All three aspects interact with one another and with the environmental characteristics of the location of deployment. Those are the technical issues to be borne in mind when weighing up competing tenders but there are several other considerations, such as:

• the vendor’s market position (how many installations worldwide?)
• its track record (how long has it been in business?)
• its breadth of product range and experience (is it a full-range or niche supplier?)
• its technical capabilities and expertise (does it have its own design department and testing ranges for both RF and structural issues?)
• its client base (how many major governments supplied?)
• its supply partners (does it collaborate with world-class radar manufacturers?)
• its global supply capability (does it have manufacturing and sales bases in all continents?), and
  the after-sales backup (does it offer lifetime maintenance support and staff training?).

Not all customers have the resources to manage the installation of these structures and instead outsource the systems’ integration issues. This is understandable, as the logistics of co-ordinating power supplies, structural contractors and materials, then erecting the support structures, radar equipment and radomes is quite formidable.

As it happens, there is in fact only one company in the world that can supply complete turnkey solutions to the defence market, handling tower, radome and civil engineering issues under single management, to any location in the world. We commend this approach as particularly cost-effective as, with our regional sites around the world, we are able to achieve significant cost savings through local manufacture and support.