This model uses RS232 data and has recently been replaced with an RS422 model.
What’s the difference between RS232 and RS422? Actually, none for most applications on a boat. RS422 is a balanced cabling system using four data paths (2x transmit and 2x receive), RS232 is unbalanced and uses 1x transmit and 1x receive.
Which means? RS422 is a noise cancelling arrangement so that when used with the correct cable (screened twisted pair) RS422 can be used up to 1230 metres distance between transmitter and receiver, RS 232 is good for 15.5 metres using standard cabling.
What does this mean if I use RS232 on my boat rather than RS422, my boat is 12 metres LOA? RS232 is preferable as the connection is simpler and works just as well as RS422. To connect to an Onwa plotter, and indeed most other make plotters, there is just 1 transmit and 1 receive connection so connecting to an RS422 device means converting the 4 data feeds to just 2. No converter equipment is needed but the wiring gets a little complicated.
So, why have Onwa changed to RS422? Much of Onwa’s custom is to the professional user, they have large vessels and use the data signal for more than one item of equipment – RS422 provides this.
Onwa KA-GC9A Heading Sensor
This is the device that produces the information to drive an electronic compass or an auto pilot. This is also needed if you want accurate target tracking on your radar and true course heading on your chart plotter. It looks like a conventional GPS antenna, and in one respect it is similar in that it uses satellites for GPS, but inside its IP67 case there is a very sophisticate device that can calculate SOG, COG, position and heading, pitch, roll and yaw and it does all of these rather well. From switch on, it gets a heading in just a few seconds. Easy as a GPS antenna to install – it has a direction arrow on the case –Install on a horizontal centre line of the boat and align the arrow the centre of the bow and it’s ready to go. It is configurable in many ways using an Onwa free APP but you won’t need to as it will come pre-configured if you describe with your order what other equipment you intend to use it with and how you intend to use it. For example, if you buy an Onwa auto pilot, a KA-GC9A comes in the pilot box pre-configured at the factory. Incidentally, older auto pilots used a fluxgate compass for position and heading sensing, but modern up to date auto pilots from all manufacturers use a 9 axis sensor device exactly similar to the KA-GC9A although they are very much more costly. KA-GC9A can operate from 5 volt to 32 volt and has over voltage and reverse polarity protection. Cable length is 9 metres (5 core cable).
Can be set to output NMEA2000 in the software (Onwa provide a free APP)
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