No GPS Signal - Hidden Seatalk Bus

[simonmoore]

My Raymarine RL70c chart plotter is not receiving a GPS signal.  I suspect there could be a problem with the antenna (Raystar 120) or the cabling.  Having checked the back of the plotter there is no direct GPS feed into it so I assume it gets the GPS signal via the Seatalk system.  I also have a combined Raymarine Radar/Plotter and this is not receiving GPS either.  The problem is I can't seem to locate the main Seatalk bus.  Any ideas where this may be located on a 2003 Bavaria 38?

[Yngmar]

There is no "main seatalk bus" with Seatalk1 (just called Seatalk then). Seatalk1 can be joined anywhere you like and requires no termination or bus and spur cabling like NMEA 2000 (SeatalkNG) does. Just follow the flat black Seatalk plug with three connectors inside from the back of the chartplotter or Raystar antenna and you'll eventually find a bunch of joints or a little three-plug connector bar.

The GPS fix will most likely be  supplied from a Raystar 120 or 125 GPS antenna, which is capable of both Seatalk and NMEA 0183 and in this combination almost always is wired directly to the Seatalk network. The antenna has a little diagnostic LED on top, which should be blinking green (fix), orange (no fix) or red (failed). If it blinks red, it may possibly need a new CR2032 battery inside, or it may well be dead - they're no longer made, so finding a replacement is a pain.

If you can't find a replacement, you can use a NMEA2000 GPS receiver and the Raymarine Seatalk converter (available), or a NMEA0183 receiver and the PC Seatalk converter (also getting hard to find). Possibly you can also wire the NMEA0183 into the chartplotter, but I haven't looked into this option, and I'm not sure it will relay it into the rest of the Seatalk network (for the SOG on the speed instrument, etc.).

[Kaptajnen]

My Bavaria 38 Center Cockpit 2000 came with the very first version of the Raynav GPS antenna, which had NO electronics - just a coax cable. This museum piece took "forever" to lock on to the GPS signals - and eventually failed.

It was replaced with a Digital Yacht GPS150, which instantly locks up to the satellites. I highly recommend this antenna as a replacement. It is easy to wire to to the Raynav system - the Green wire from the GPS150 to the Raymarine Green and the GPS150 Yellow to the Raymarine White wire.


http://digitalyacht.co.uk/product_info.php?products_id=11706

Product info:
----------------------------------------------------
GPS150 (NMEA OUTPUT)

The GPS150 DualNav? positioning sensor combines a super accurate 50 channel GPS with GLONASS, the Russian funded satellite positioning system that is now on line and providing an excellent back up or alternative to GPS. This ?smart? sensor will automatically switch between the systems or the user can manually select the most appropriate for their activity. The GPS150 will also be able to utilise the European funded Galileo positioning system when it comes on line (IOC ? Initial Operation Capability in 2018).

The implementation of GLONASS as an additional satellite positioning system is probably the biggest step change in maritime navigation since GPS was fully augmented back in the mid 90?s. Digital Yacht?s GPS150 utilises the industry standard NMEA data format allowing older chart plotters as well as current generation products to take advantage of this new technology. The GPS150 also allows the user to select a variety of different NMEA baud rates (4800, 38400 and 115200) to allow interfacing with legacy and current systems. It also supports a new TurboNav? mode which will appeal to racing yachtsmen and performance users where GPS/GLONASS data is output at 10Hz (10 x faster update than normal) and with an interface speed of 115200 baud which is 24 x the speed of normal NMEA data. This massively improves slow speed navigation data as well as providing the best course and speed data in a dynamic situation.

The GPS150 houses all the electronics in its compact 75mm antenna and has a single multi core cable for power and data. Power consumption is just 30mA at 12V. It can be used as a simple positioning sensor for plotter or VHF DSC systems as well as a precision, high speed sensor for performance sailing/super yachts. Setup is easy with a block of simple internal switches setting the characteristics of the unit. This allows the device to be programmed in the field without specialist software or programming tools.

The GPS150 can also connect to the WLN10 wireless interface to allow data to be sent to mobile devices such as iPhones, iPads and Tablets. There is also a USB interface for PC and MAC users (ZDIGUSBNMEA).

FEATURES

50 channel precision GPS/GLONASS positioning sensor
Just 75mm in diameter and designed to fit industry standard 1? mounts
Ultra tough, waterproof construction
NMEA output configurable for 4800, 38400 and 115200 baud
Selectable update rates from 1 to 10Hz
Configurable in the field using simple DIP switches inside the antenna
TurboNav mode offers super fast updates to optimise positioning information in slow and high speed applications
WAAS/EGNOS/SBAS enabled for sub 1m accuracy
User selectable GPS/GLONASS mode or auto selection
Ultra low 30mA power consumption (at 12V DC)
5-30V DC power input


Claus

[simonmoore]

Thanks you both for you excellent replies.