Devices which automatically report a GPS position would be the biggest improvement.
“DF”?...Later we would add DF for 406 MHz, and eventually for almost all voice freqs (including VHF)...
There is triangulation going on. Otherwise, all you have is a bearing to the received signal.Is that the technology, which was weak, or is there some triangulation going on?
The RF signal provided one line of position. A second LOP is needed to narrow down the precise location. Often this could be from a commercial AM radio station, which RF direction finders could receive in addition to the USCG maintained stations.I’m sorry to be overly inquisitive, but the term DR congers up memories of RDF navigation of yore. Is that the technology, which was weak, or is there some triangulation going on?
There are no well defined standards for the world of personal locator beacons. It really pays to delve into the details. For years, PLBs were simply smaller, lower powered EPIRBs which transmitted a signal to the International Cospas-SARSAT system. The downside to this is the time delay between notification and response which can be measured in a hours.Personally I think this is a better solution than a PLB that is designed to only transmit a low powered signal to the boat you fell off of. ...and you can also use it as a radio.
Back in the day, a bearing to the received distress signal was all we had - and was surprisingly effective. I simply flew the line of bearing to the subject we were looking for. Actually I liked to deliberately offset about 5 degrees, and then observe when the line of bearing changed significantly. That gave us self-produced triangulation.There is triangulation going on. Otherwise, all you have is a bearing to the received signal.
Clearly the MOB1 device has advantages over the DSC handheld (such as battery life and possible automatic activation) but at the risk of asking someone else to do my research, what is the difference between the range of a handheld DSC signal from just above the water's surface to the range of an MOB1 AIS signal (assuming the same receiving antenna height)? Aren't they both VHF signals subject to the same limitations?The device I referenced earlier, Ocean Signal MOB1 sends a DSC emergency signal and GPS location to the mother ship's VHF which sets off a loud alarm and transmits an emergency AIS signal to all boats within the reception area (about a 5 mile radius) with the GPS coordinates.
Yes, they both broadcast in the VHF range, however, transmitting data is more efficient than transmitting voice. Additionally the MOB1 is designed to have the antenna more or less vertical while floating in an inflatable, the handheld requires a conscious effort to hold the antenna vertical. The AIS signal will continue to broadcast until the battery runs out or it is shut off. The DCS signal only broadcasts until someone aknowledges (I think.) The MOB1 will work if the COB is unconscious or otherwise impaired.Clearly the MOB1 device has advantages over the DSC handheld (such as battery life and possible automatic activation) but at the risk of asking someone else to do my research, what is the difference between the range of a handheld DSC signal from just above the water's surface to the range of an MOB1 AIS signal (assuming the same receiving antenna height)? Aren't they both VHF signals subject to the same limitations?