Well, actually, you don't need it anymore. We recently sold our CARD unit. Our replacement was in 2 parts
: the Sea-Me active radar
reflector (which also detects but without showing bearing to target) and AIS
, in addition to our own radar.
When the Sea-Me beeps, you look on AIS to see who/where it is. If there's nothing, you switch on radar to find it.
The whole radar detection thing is only usable with off shore passages because it will be beeping full time when coastal, even in remote parts