On Thu, 25 May 2006 18:48:03 -0400 Larry wrote:

AIS is a TIME SYNCHRONIZED slot data mode, similar to TDMA cellular phone
technology, not a bunch of serial data sent at random like NMEA uses. It
requires the attention of the AIS receivers and synchronizing modems at all
times with no time for scanning other channels, as you infer. The NMEA
sentences any AIS receiver generate are not what is transmitted on the air,
no relation at all. The receiver decodes the AIS data stream, time
synchronized from all users, and a separate circuit generates the NMEA
serial data stream with its headers for NMEA devices to use.

It's not going to come out of your VHF radio. Put that out of your mind.
I suspect and hope all boats over 30' carry transponders in the near
future, with NMEA chart plotter output if we have to stick to such archaic
technology.

I see no reason why we can't have a VHF set with integrated AIS receiver and
your message does not tell any reason for that either. Obviously the set
should have dual receiver circuits, the other for AIS data channel and the
other for normal traffic.

matti

--
"China is a big country, inhabited by many chinese." - Charles de Gaulle