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DSC St. one more

Vernon Matheson
 


Called MMSI station address: 003669997 [Coast station: Miami FL MRCC Miami FL, MRCC Norfolk VA] (USA)
Category: Safety
MMSI self-identifier: 003769997 [Coast station: St.  (Saint Vincent and the Grenadines)] (Saint Vincent and the Grenadines)
Telecommand 1: Test
Telecommand 2: No information
Neither RX/TX frequencies nor position supplied
Check Sum: error
Date and time of decoding: 02/20/2014 22:39:56


If you notice the DSC ID is out by 1 digit     00366 for Miami   and 00367 for the St. ID

Could Mulipsk be reading it wrong or is the ID number allocated to St. Vincent area

John Pumford-Green
 

Hi Vernon,

Your original message from the South African coast station:

<Selective call to a particular individual station>
Called MMSI station address: 601165200 [Ship] (South Africa)
Category: Routine
MMSI self-identifier: 006010060 [Coast station: St. (South Africa)]
(South Africa)
Telecommand 1: J3E telephony
Telecommand 2: No information
Neither RX/TX frequencies nor position supplied
Check Sum: OK
Date and time of decoding: 02/20/2014 04:00:04

This had no name for the Coast Station and it appears:

006010060 [Coast station: St. (South Africa)]

because MultiPSK has no listing for the MMSI 006010060, but it knows that "601" is "South Africa". My guess is that "St." appears as MultiPSK's default name for MMSIs that aren't in its look-up table. Unlike DSCDecoder and YaDD it isn't possible to inspect or edit this look-up table in MultiPSK.

The message was genuine though, because of the line "Check Sum: OK" and we have found that the MMSI belongs to a commercial marine company "Imtech Marine, Port Elizabeth"

Your other messages where the coast station name is shown as "St." are all false decodes.

Taking each in turn

<Selective call to a particular individual station>
Called MMSI station address: 003669997 [Coast station: Miami FL MRCC
Miami FL, MRCC Norfolk VA] (USA)
Category: Safety
MMSI self-identifier: 003369997 [Coast station: St. (Haiti)] (Haiti)
Telecommand 1: Test
Telecommand 2: No information
Neither RX/TX frequencies nor position supplied
Check Sum: error
Date and time of decoding: 02/21/2014 05:07:21


This one has a Check Sum error, which means that although there were a full set of valid symbols - one or more of them has been decoded wrongly and the overall message checksum has failed. It's likely that at the very least the self-identifier has been decoded wrongly and probably should be 003669997 - Miami doing a test call with itself - happens quite regularly.

The next one:

<Selective call to a particular individual station>
Called MMSI station address: 314012000 [Ship] (Barbados)
Category: Safety
MMSI self-identifier: 007251861 [Coast station: St. (Chile)] (Chile)
Telecommand 1: Test
Telecommand 2: No information
No control by check sum.
Date and time of decoding: 02/21/2014 06:30:30

Here we have "No control by check sum." which means that there weren't even a full set of valid symbols produced by the decoder, and MultiPSK therefore knows it's not worth considering the overall message checksum. One or more parts of the message are missing, although MultiPSK doesn't give us enough information to know what. YaDD is much better in presenting the user with the full set of raw data.

Again the Coast Station name appears as "St." because the MMSI that appears is 007251861. The "725" refers to Chile, but 007251861 isn't a known Chilean coast station. However, Valparaiso has the MMSI 007251860 - perhaps the final symbol of the MMSI has been wrongly decoded, and the message was from Valparaiso? It's not possible to know for sure, many other symbols might be in error.

The next one:

<Selective call to a particular individual station>
Called MMSI station address:003669997 [Coast station: Miami FL MRCC Miami FL, MRCC Norfolk VA] (USA)
Category: Safety
MMSI self-identifier: 003769997 [Coast station: St. (Saint Vincent and the Grenadines)] (Saint Vincent and the Grenadines)
Telecommand 1: Test
Telecommand 2: No information
Neither RX/TX frequencies nor position supplied
Check Sum: error
Date and time of decoding: 02/20/2014 22:39:56


Again "Check Sum: error" which means that although there are a full set of valid symbols to play with the overall message checksum has failed the test. There is at least one error, posibly more.

The reported MMSI 003769997 would belong to St. Vincent.... because "376" is the "MID" for that country. Again the Coast Station name appears as "St." because MultiPSK has no record of who owns 003769997 - which is hardly suprising, as it doesn't exist.

As you've spotted, 003769997 is very close to 003669997 - which is Miami, and this could probably be another test call from Miami to itself.

The upshot is - unless you see "Check Sum : OK" then you can't trust that any of the presented information is correct, and you can't tell which are the broken bits of the message, so you should discard it.

YaDD presents much more information with which it's possible to do a bit more detective work and often you can calculate to a good degree fo certainty what the errored message should really have been. You can't do this with MultiPSK. MultiPSK is undoubtedly more sensitive, Dirk himself agrees, but for my enjoyment of DSC you can't beat YaDD for letting us delve into the subject in a bit more depth!

Still, I'm very impressed with the report of "MMSI self-identifier: 006010060 [Coast station: St. (South Africa)] (South Africa)" which is a first.

Have you considered sending them an email - I'm sure they'll be interested in your report of receiving them, and you might be able to get some information of their setup :-)

Cheers,

John
GM4SLV

If you notice the DSC ID is out by 1 digit 00366 for Miami and 00367 for
the St. ID

Could Mulipsk be reading it wrong or is the ID number allocated to St. Vincent area