When choosing a radar reflector look for published proof of response as many claims are unsupported. Some popular tube reflectors were found to be “invisible - a useful addition to a stealth bomber” in the West Marine sea trials published on the internet. Echomax publish QinetiQ response diagrams with every radar reflector offered for sale.
Radar reflector response depends on the mounting height of both radar reflector and transmitting radar and of course the weather and sea state.
Passive radar reflectors return the weak or strong radar signal received
Sea trials by the RNLI on the EM230 Basemount fitted to an A frame 2m above sea level on a RIB recorded 100% response at 3.8nm and 80% at 5 miles plus – a radar reflector response mounted on a taller mast would have a more distant horizon. The horizon at 5ft is 2.7nm
The RORC recommended mounting height where possible is 4m above sea level
MCA sea trials on an EM230 – at 5nm plus gave 100% to X band radar and 80% to S band radar
Motor vessels – passive radar reflectors
Smaller vessels , RIBS 5-9m the Compact or EM230BM with base mount fixing and optional navigation light offer an easy solution. If the vessel has a mast the new EM180M with mast brackets is another choice.
The EM230 with Ships Wheel Mark certification for life boats and rescue craft is popular for larger vessels and can be fitted to a vertical mast or wheel house roof with an optional deck bracket
Sailing vessels – Passive radar reflectors
Small yachts up to 8m the new EM180 Midi or EM230 Midi with mast brackets is a good choice and a for larger vessel the EM230 which can be mast fitted or suspended from the cross trees to eliminate mast shadow of 22 degrees and retain full reflector response when compensated and sailing to windward.
Active X - XS radar target enhancers – these can be fitted to any vessel and draw a miserly 15-26mA on standby
Active RTE receive and amplify the radar response within the ISO8729-2 specification.
Active-X responds to 9.40 GHz X band radar which is fitted to pleasure and commercial vessels up to 3000GT. We call this the collision avoidance radar
Active XS responds to 3.00 GHz S band radar, which is compulsory (in addition to X band radar) on vessels over 3000GT, for deep sea use against snow, heavy rain etc. 3000GT or larger vessels cannot stop or change course quickly to avoid you. The control box has audible and visual alarms which will identify and display whether a X or S band radar, or both, is/are painting you. Both X and XS control boxes have an 8a volt free extension alarm facility.
Fit the Standard mast bracket for the Active X and the XS Ocean bracket for the Active XS – do not use other makes as we started with these but after having 5 break after 18 months designed our own
If you sail offshore or in or near busy shipping lanes you should consider fitting the Active XS.
On the Active FAQ page there is a summary of AIS v RTE strengths and weaknesses both being useful safety aids for offshore sailors, also comments by Ross Hobson on the much earlier response of his XS than the AIS racing in fog were quite enlightening.
Please also read the Active - FAQ section regarding reduced responses to FMWC - broadband radar.
Active RTE may be saturated within 250-300m by large vessel radar - but proper visual look out should never allow this to happen and the RTE was never designed for this type of use.
Never assume that ships see you – the Dutch Coast Guard advised that they were in a helicopter hovering for 20 minutes above the bridge of a large vessel through the Dover Straights and at no time was there anyone on the bridge!
RTE - Active Location
The drawing below shows where the X or XS should or should not be fitted. The Active X or XS must never be fitted within the 28 degree radar horizontal beam width. Many sailors particularly single handed prefer lower mounting as the mast head gives a distant horizon and can make the use of the audible alarm tiresome. Some use rail mount with a fixed or QD rail bracket and possibly an extension pole of 60cm to obtain a more distant horizon. Since this drawing we have made a suspended version which is an option subject to sail and rigging configurations being kept well clear of the RTE cable.
You may find this YouTube video by Sailing Britaly informative