I did further tests of DSC
emulation with the E120W "Cancel Distress
Call Type 16" msg and actual tests to OCPN and E120W with my VHF radio
First on the E120W -
Emulation of the Cancel Distress
msg with 16 as the Call Type (field 2) and 12 as Category (f4) = This does NOT cancel a Distress msg or a Position msg which is already displayed on the screen
. If there is no existing msg on the screen
the 'Cancel Distress' creates a new Distress popo-up.
Same msg as above but changing f4 to be 16 instead of 12 = same results as above.
Other reactions noted:
A Distress msg will over-ride a Position pop-up already on the screen.
A Position msg will over-ride a Distress pop-up already on the screen.
Now to REAL tests with my radio
. It is a GME DX600D manufactured 2013 and specified as 'Class D'.
I used the DSC
call 'POSITION REQUEST' and received an auto response from 2 different vessels. The replies were clearly seen on the VHF
radio screen and data was sent to the connected plotter, but neither OCPN or the E120W reacted to the DSC data.
I captured the data and found my radio was outputting $CVDSC instead of the expected $CDDSC. Here is a capture of the data:
So it appears both OCPN and the E120W are 'fussy' about the Talker ID being specifically $CD for these messages. I always imagined NMEA
listener devices were quite 'broad-minded' about talker IDs so long as they started with $ and were 3 chr total since there is often overlap of NMEA
msgs from different types of instruments/devices.
PjotrC can you confirm that OCPN needs to see $CD exclusively as the talker ID. Any chance that can be opened up to accept other ID's such as $CV?
I have emailed GME asking why they use $CV instead of $CD and if it can be changed, but no reply yet. I have seen $CV listed as a Talker ID for VHF radios but the same list shows $CD for DSC talkers.
It also seems Raymarine
requires the $CD ID exclusively too. I have emailed them to ask if they accept other talker IDs for their DSC msgs but no reply from them either.
I wonder if anyone else out there knows of VHF-DSC radios which use talker IDs other than $CD?
When/if I get replies from GME or RM I will report back.
In the meantime, all this testing is very interesting but it looks like I have a radio and 2 navigation
plotter which don't want to talk!