[DG] [DG11] No SOG

[michaelb_harvey]

No SOG displayed after start up
I have a ST60+ system with some additions

ST60 Wind speed & direction (2002) (new masthead transducer installed 2014)
ST60 Close hauled (2002)
ST60 Tri-data (2002)
ST6000+ Auto Pilot (2002)
Graphic display (2010)
AIS 500 (2010) with supplied dedicated gps antenna
E90W MFD (2010) with original (2002) Raystar 120 gps* (new battery installed 2018)
Lifetag system (2010)
Radar 4KW 24” radome (2010)

All above were installed by Raymarine main agents in UK

*This gps antenna was originally fitted to the yacht when she was new, and used with an original RL radar/plotter display

Until recently for many years everything worked fine, then after sailing out no SOG on the MFD or anywhere. COG always showing.
I tried restart gps but I do not think that is the problem, and anyway since changing the gps battery the position acquisition is very fast.

I tried switching off the system then on again and eventually (although maybe not as a result of the switch on/off) , the SOG appears.

Any ideas?

Thank you.