New Technology Radar
NEW TECHNOLOGY (NT) RADAR, A QUIET REVOLOTION?
A Brief History
Marine radar has been with us now for over 60 years, although it was only around 50 years ago that the Merchant ship owners reluctantly (also with somewhat surprising resistance from ships’ Masters) introduced radar onto their ships. Even in the 60’s some shipping companies refused to fit radar (Blue Star Line resisted the longest on the basis that radar led to lazy watchkeeping) and on my first trip to sea in 1969 the radar installation was an already antique Marconi Mk4 whose valve driven electronics occupied a whole mast-house on the main deck. Setting up this geriatric equipment to produce a picture required the “Sparky” to be in attendance in the mast-house to tweak up the tuning on an oscilloscope! He was not a happy man, not least because having spent around 15 minutes setting the system up the Captain would get the Mate on duty (he didn’t understand it) to take a bearing and range from the land and then promptly switch it off to “save it” only to repeat the process around one hour later. The poor Sparky became hysterical in trying to explain that valves lasted much longer if they were left running and the fastest way to destroy them was to switch them on and off at short intervals. Needless the say the Captain was never convinced but somehow managed to survive the five month voyage without being murdered by the Sparky, although at times it was a close call! Fortunately the Captain only allowed the radar to be used in poor visibility making a landfall. In fog out at sea he preferred to have us apprentices posted on the bridge wings and forward keeping our ears tuned. We heard a lot of ships and got very cold but by proceeding at a safe speed of Dead Slow ahead or stop we managed to avoid all other shipping. There are probably many investigators who would recommend a return to those old techniques! As for the quality of the radar picture I never really got to find out because as a first trip apprentice the only time I was allowed on the bridge was during harbour stations and to clean the considerable amount of brassware! The radar set was hidden behind a thick black curtain and when in use the subdued murmurings from within was reminiscent of a church confessional. Although the compulsory carriage of radar in Merchant ships was not a requirement until the implementation of the 1974 SOLAS Convention in 1980, the fitting of radar became standard practice as ship owners recognised the benefits it provided in navigational safety and efficiency! Consequently during the 1970’s advances in the technology and quality of displays was rapid. The old reflection plotter was replaced by various electronic plotting aids (remember those matchsticks?) and the basic ships Head Up mode was supplemented by the gyro stabilised North Up displays and true motion facilities. The introduction of transistorised circuits enabled the electronics to be fitted into the radar casing and although the reliability was not that great the Sparkies were generally able to return to their hermit lifestyle in the radio room. This rapid advance of course gave free reign to the manufacturers who started introducing additional features to sell their sets. The actual needs of the end user gradually became sidelined and the many voices urging standardised control panels and display layouts were ignored. The early 1980’s saw the introduction of daylight displays and this, coupled with further advances in electronic circuitry permitted it to be released from the confines of its black curtained shrine and be incorporated into a bridge console. Since then the merchant radar has generally evolved to the agenda of the manufacturers to the point where almost every radar now encountered has a different mode of operation and a bewildering array of controls from the traditional but feature crowded keyboard to touch screens and the rollerball and button systems. In the bid to provide “sexy” new functions, the basic needs of the navigator have now been almost totally lost with even some essential features such as heading marker suppression being relegated to unfathomable depths within a myriad of sub menus! As pilots of course we see them all and I am sure that I am not alone in observing that it is now common to find Masters who have no idea how to find some features and it is not even worth pilots considering trying to set up parallel index lines on most sets!
The situation today
Despite all the advances in displays and additional features the actual means of providing the radar image is basically unchanged from the first military radars of World War 2. Currently all radars are still dependent on high voltages being applied to a magnetron to generate a very high power short pulse and the only difference now is that prior to being sent to the display the raw radar returns are usually digitised to clean them up whilst automatic gain and tuning processors then work on the digitised signal to provide further cleaning to produce a “clean sweep” display. Whilst these facilities generally compare well with the old manual “tweaking” of these controls they can result in small targets remaining undetected in choppy conditions and although it is recommended that watchkeepers regularly switch to manual adjustments to check for small targets it is apparent that many watchkeepers don’t. It is possible however that these auto features may be reviewed in the light of the MAIB investigation into the sinking of the yacht Ouzo (apparently following a collision or very close quarters incident with the P&O ferry Pride of Bilbao), which, upon examining the radar data at the time of the incident, found that the radars had never detected the Ouzo indicating that the target had been lost in the (force 5) sea clutter.
The easy answer is complex electronic wizardry but your dedicated editor has spent a bit of time trying to understand the basics in order to make the following explanations as non technical as possible.
The main problem with a magnetron system is that the pulse generated is unstable and this results in a severe limitation of performance and also means that only the amplitude of the returned pulse can be utilised to detect a target. Magnetrons are also expensive and, with only around 10,000 hours operating life, require regular replacement. By using a long, low powered (voltages can be reduced to around 25 -50 volts) and stable pulse, target detection can be improved, especially in sea clutter. Although low power radar has been in use for some time with the military these are generally continuous wave rather than pulse systems which require very complex and therefore expensive receivers to analyse the returned waves for target detection. The major problem with using a low power long pulse has been that at the shorter ranges the return from the target starts arriving at the receiver before the transmitter has completed transmitting it and this resulted in early units being unable to comply with the IMO specifications. Whilst all manufacturers have been working to resolve this issue it is Kelvin Hughes who have managed to produce the first commercial NT radar which they have called “SharpEye”.
How does it work?
Basically traditional radars generate a pulse of around 1 microsecond in length but by using a pulse of 1 millisecond, the power needed to generate it is around 1000 times less. Therefore, instead of an intense high powered short pulse of around 25 KW, the SharpEye produces a low power long pulse of around 170W. The other key advantage of this low powered pulse is that it can be made extremely stable by modern processors which also permit the generation of very complex and variable waveforms. This “coherency” of pulses also enables the receiver to detect phase shifts which further reduces the power requirement for the pulse to provide “traditional” performance. The phase shift detection is the Doppler effect which means that as well as just detecting a target its movement towards or away from the observer can be analysed and it is this feature which permits the vast improvement in small target detection in sea clutter claimed by the manufacturers.
The ability to generate extremely complex but stable waveforms is also what resolves the problem of detecting targets at close range. Again in simplified terms, NT radar generates different waveforms for each pulse which effectively gives them a unique code and as each of these unique pulses is transmitted the receiver is alerted to recognise it when it returns. Other returns, which cannot be recognised, are therefore disregarded. The returned recognised pulse is then electronically compressed into a very short pulse thus providing the IMO short range detection requirement.
Conclusion
NT radar promises to deliver enhanced detection from more stable and therefore cheaper technology and the following tables have been produced by Kelvin Hughes comparing the performance with existing magnetron based radar. Another advantage for ship owners is that the SharpEye unit is compatible with existing KH scanners and displays.
For those of you who wish to learn more about the technology, full details can be found on the SharpEye website at :
For some reason you need to register to enter the site but registration is free.
JCB
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