On Sun, Jan 6, 2019 at 02:20 PM, Richard Ware wrote:
Yes, I presume the VHF system works in a similar way to the MF one.The systems i know of keeps track of two parameters, the position and signal level from the DSC call.
The operator might manually choose the site/channel based on distance and propagation properties, or relay on the automagic function that uses the signal level for voting the right voice channel/site.
This automagic facility is quite good, if the non purely line of sight connections, day night propagation differences and noise levels on MF and HF is disregarded. When dealing with these the coast station operator has to fall back to operator skills and experience.
However, it have one drawback which i have noticed mostly during summertime when doing radio surveys. Sometimes the system automagically chooses a VHF site 30-40Nm away but with a stronger signal on DSC at that particular moment, than the site 5-10NM away which was slightly weaker.
When trying to do the voice part of the call it simply wont go thru, or is really weak, and the lack of coast station operator skills becomes obvious.
On MF it might be even funkier.
Previously the sailor could manually choose to test to a more distant coast station and get a feel if the transmitting and receiving function is proper. When the selection is automatic the sailor has to call the strongest station by DSC and ask for a more distant voice connection, which is rarely done in reality.
So they might have quite rotten equipment, transmission lines or antennas without knowing it.