Thanks. Great input.
I am wondering if Radar is really all that important. We have a lot of ship and barge traffic on the Patapsco and Chesapeake which is the main reason I was thinking about Radar. I hate it when those big fellas sneak up on you. For that purpose would an AIS transponder be cheaper and easier to use? What is the main use for Radar?
AIS won't replace radar for collision avoidance, especially here in the Chesapeake around Annapolis. I'd guess I see maybe only 1% of boats around here -- or maybe less -- have an AIS transmitter.
Also, I watched a small fast boat cross our path, and the time lag on his Class B transmitter was such that the first hit (that I noticed) on our plotter was 500 yards to port, and the second hit was about 800 yards to our starboard. That was sort of an eye-opener.
OTOH, the AIS info is very useful for knowing who's where; makes it easy to call a tug or ship by name and expect an answer. And you can use their plots/course in a predictive way, to modify (or not) your own course if necessary, even without discussion.
Radar, on the other hand, can be used for collision avoidance -- especially at night, in fog, or in heavy rain, but also in clear daylight. I can use the radar as a rear-view-mirror even on clear days, so I don't have keep looking behind quite as often. And/or I can set guard zones so the unit gets my attention if traffic approaches into our settings.
Radar can also be used for rough navigation, too, especially in limited visibility. For example, a shoreline will show up clearly... and that can be used to confirm location...
We boated on the Chesapeake for many years without radar; wouldn't be without it, now. Previously, that meant if it were foggy, we stayed in port... and we avoided moving on those dead black nights where there's no moon, no stars... The first time we critically needed radar -- but didn't have it -- was on Delaware Bay, returning from Lewes, on a schedule. Heavy fog, couldn't see the front of the boat. Argh!
Since then, different boat, we now have radar, all better... and we use it routinely here; if we're moving, radar is on. Had a repeat of that Delaware Bay trip a few weeks ago, couldn't see the front of the boat. No hard schedule, this time, but we could "see" ship traffic on both radar and AIS -- and they could see us -- so it was much better and we made the trip even in those conditions. (It also helped to have our VHF radio/fog horn going.) There's still an "Argh!" factor in conditions like that, but less so.
-Chris