AIS transcievers are expensive and really only necessary for those who like to sleep when undersay in high commerial traffic areas. They will tell a ship where you are and let you see on the
screen where they are and what they are. Something that can easily be done with the Mark ! eye ball for
day sailing and coastal cruising. Yes, if you have a bunch of money left over from
buying the necessary things to go sailing with by all means get an AIS. If you sail in an area with perpetual fog/poor visibility and
commercial traffic, might put it higher up the list.
Chart plotters have gotten rediculously
cheap. They are built for the marine
environment so you can locate it where it will be useful from the
helm, can be seen in sunlight, without fear of an errant wave wiping out your
navigation or having it slide off its perch and shatter on the sole. Have had no luck with Open CPM for a plotter. It's not intuitive for me and find my fossiized brain can't make it
work. The first time I used a plotter, turned it on and sailed 50 miles on the open ocean and through one of the busiest
ports in the world, easy peasy.
Depth sounders are necessary little devils. Tell you which way things get shallow, warn you of approaching hard things and tell you how much
anchor rode to layout for a secure nights sleep.
I like a knotmeter/log. Tells me how I'm doing harnessing the
wind and how far I've gone. Necesary for DR
navigation and estimating position in conjunction with a depth sounder if the
electronics or your source of electricity goes tits up. Not really a must have but I don't leave home without it.
Fixed position VHF radios are the last thing I'd spend money for on a boat. A radio that is down below can't be heard or at least understood from on
deck. You can't transmit without an expensive problematic
remote mike. Since it's down below and I'm mostly on
deck it's almost totally useless for me. A
water proof, floating handheld VHF can be clipped to your belt or put in a cubby in the cockpit. It is always ready for use their and can be easily heard but you do have to remember to keep it charged. Only negative to a handheld is it doesn't have as great a range as a built in with a masthead
antenna but its range has covered everything I've needed. If I want range for an
emergency will set off one of the epirbs.
Personal
Epirb clipped to my harness/inflatable vest. Will alert the powers that be almost instantly if there is trouble that can't be handled. Try to clip on when I'm sailing alone but will locate me if I should somehow go over the side. Cost on the personal units have come down and have everything needed with enough transmit time for the CG to find you.
The rest of the electronic gizmos are nice to have items.
Radar is useful in
fog if you like to scare yourself seeing all the crazy
power boaters zipping around at flank speed with no visibility. Find the GPS more than accurate enough to navigate in poor visibility.
You are already into HF
communications so a Marine
HF radio is an unneeded additional expense unless you have to transmit on the designated marine frequencies.
Windspeed/windpoint
instruments are expensive and don't do a lot more than a masthead Windex and a
Beaufort scale printout for estimating windspeed.
Switch all your lights over LED's, buy a small
solar panel and you will be energy self sufficient.
Have fun and sail the crap out of that boat.