Military and Commercial
international flights routinely guard 121.5mhz AM and can be useful in an emergency because they have truly huge lines of sight at Flight Level 350 (~35,000 feet). Effectively a very high radio
I've also thought a lot about the 'what if someone goes overboard' scenario. At night, I think a strobe light is far more useful than an EPIRB, even the new 400mhz sat EPIRBS only reduce the search area to around 5km CEP, though that's a major improvement. I don't think it would be at all practical for a cruising couple to RDF the position of someone overboard.
Consider that the person still on board has to handle the boat and visually search for the person in the water
. Picture doing that and trying to turn dials and such to get a bearing on a transmitter in the water. Not easy at best and I'd say impractical.
A simple strobe light attached to your lifejacket would be great at night, a smoke flare or two during the day and a simple canned air powered foghorn would be great as well. All low tech and don't require you to be inside trying to read an S meter or a bearing instead of driving the boat.
I'm going to look into making something small and automated that will do something like it. There are plenty of matchbox or smaller sized GPS
units around. Sounds silly, but you could attach, say, a waterproofed 'mouse' gps
with a serial
output to something like a TinyTracker APRS gizmo, and a small transmitter, say, 250mw or so in something like the 400mhz ISM band to a headband or the top of the PFD
. Range of about a click most likely. If you want to be tricky, perhaps make it water activated. Some APRS software
and you are in business. The person in the water would show up as an APRS position on a 'radar' display and it would be fairly simple to go almost directly to them, without having to do any fiddling with DF (which is not as easy as it appears).
You could do it with DSC
but AX25 1200bps packet is relatively simple to generate, a crappy old scanner with nothing more than a line out from the headphone to the soundcard on a computer (or an old TNC if you can find one). At it's simplest level, a TNC connected to a serial
port with Winterm will display the received APRS packets as text, with the position, punch it into the GPS or chartplotter
There would be issues, the GPS and and the TX antenna need to be out of the water. So does the person's head
, so somewhere on the upper body or head for those bits. Probably not that hard. Waterproof the whole thing. There may be commercial
things out there smaller and better engineered and already waterproof, but not everyone can afford commercial equipment with big price
tags aimed at the oh so wealthy cruisers of the world (lol).