I purchased a cheap second-hand radar that has been of limited value - though that’s partly my fault. But the whole purpose, other than the toy-factor, was for a learning experience. I probably mounted the antenna too high on the mast which created too large a dead zone around the boat, for the in-close information I needed in the dark and fog of lower Multnomah Channel and Scappoose Bay. And the way I first mounted the display, I couldn’t really see it from the helm. It takes some practice to recognize what you’re seeing, and most small boats don’t seem to show up at all. Radar also has other uses such as tracking squalls and measuring your anchor circle in tight anchorages.
There are also some books out there to teach you how to get the most out of your radar. I’ve purchased a couple.
Sparks, Radar Made Simple For Cruisers. I cannot recommend this book. While it hints at some practical ways to use radar, beyond “steer around the dots,” the writing is awful and riddled with errors, including whole sections of text misplaced and repeated. It doesn’t seem to have been edited at all. The author’s idea of “math shortcuts” seem strange and confused to me, when the original calculation was straightforward. Most of the information could be found more easily simply by reading the manual for your equipment.
Burch, Radar For Mariners. From the prolific author and Starpath school guy. I’d like to report that this is the better value, but I confess that it is still in my “to be read” pile. I’ve only skimmed it a bit.
I’ve had AIS for several years now and it is great when it works. It shows me commercial shipping long before I can see it, on the River. And I can be certain that commercial shipping sees me. But most private boats (and even commercial fishing boats) still lack AIS. And too many of those that do have it seem to leave it turned on all the time at the dock. One thing to be careful of is the time since last signal. Class B units might only send a signal once every six minutes. Boats can move a long way in six minutes! Sometimes a target will show up on the display, but when you interrogate it, that signal was “last detected 2 hrs 19 min ago!” Where is it now? And forget about clowns who try to tell you that they can just use web-based apps on their phones. That’s for entertainment purposes only.
Bottom line, neither AIS or Radar is a foolproof system. If I was buying only one, I’d get AIS. More bang for the buck.