How has digital radar developed and what benefits does it offer us?
Whilst there have been huge advances in chart plotters, GPS and AIS, technological advances in radar have been less apparent. However, the introduction of digital and broadband radar is set to simplify radar use and make the picture easier to understand.
Radar sends out a pulse of energy in the form of a microwave on the 9Ghz wavelength. This pulse of microwave energy reflects off any targets and bounces back; the time taken for the signal to return allows the processor to calculate range. Big solid objects reflect the pulse better than small wooden or GRP ones.
Each pulse lasts less than one millionth of a second but the length of the pulse varies depending on the range that the radar is set.
Creating pulses of microwave energy and sending them long distances requires high power, so most small boat radars are about 2Kw (2000watts). Whilst high energy goes out, the returning echoes are very weak.
The radar receiver amplifies the weak returning echo to ensure that weak targets show up along with the strong ones. A problem with amplification of weak echoes is that any stray unwanted radio waves or noise that is also received is also amplified, therefore reducing the integrity of the echo and radar sensitivity.
Most radar manufacturers are now advertising HD, Super HD or SD radar and whilst they all differ slightly the main similarity is that they digitise the incoming data from the returning echo. The incoming echo arrives at the radar in a basic analogue form and digital radars digitise the returning echo so it can then receive greater processing to extract cleaner and enhanced data.
Because the signal is digitised, often manufacturers rate the displayed signal strength using colour with red the colour of choice for strong targets through yellow to green for weaker ones.
This Digital Signal Processing (DSP) offers a clearer picture with better definition of targets and less clutter.
This greater clarity would not be able to be displayed without similar advances in screen technology. Early pixelated displays that gave a block like target representation have now been replaced with high resolution screens allowing this greater detail to be displayed.
Digital radar combined with a high resolution screen produces a significantly improved picture. With less clutter to worry about on the radar screen and a clearer picture, software engineers have developed auto tuning software that is able to get a better picture.
All this is making radar simpler to use and easier to interpret.
By Simon Jinks, RYA Yachtmaster™ Examiner and Journalist
Many thanks to Raymarine for the Radar image. www.raymarine.co.uk