[TheList] HF DSC

Sun Jan 2 12:40:46 AEDT 2011

Hi Andy
I guess you wouldn't remember me for the short time I spent with North Comms after my initial training period with you and the other training staff.
Anyway, I subsequently left and rejoined the Maritime Safety Organization after being made redundant when it changed hands from Telecom to BCL (which was why I joined your organization) and BCL eventually becoming Kordia.  So it was a shift from Auckland to Wellington where I still reside and doubt very much that I'll be heading back Auckland way any time soon.
I digress......... in answer to your question below (sorry it's taken so long to respond, it's was one of those years) I hope this enlightens you and others who may have been interested:
1. The first message is an incorrectly formatted station call from MMSI 412081780 (Zhuohai/BUWO) to Shanghai MRCC.  Zhuohai should have indicated the R/T frequency they wished the subsequent communications to be on.  It was also sent on the wrong frequency as the Category for the message was only routine, at a minimum it should have been Safety.
2.  The second message is an Urgency Geographic area call transmitted by RCC Australia/VIC and which preceded their Pan Pan call on 8291 kHz, as you mentioned.  This was the correct use of DSC.  And one would hope so since the communications unit is run by Kordia.
3.  You are correct, there is a lot of DSC test traffic.  Probably more than there should be.  We see on average 6000 - 7000 messages a day on the DSC frequencies 4/6/8/12 & 16 MHz.  Most are either incorrectly formatted or on the wrong DSC frequencies.  Correct procedure is for ship stations to test their DSC units once a week and only on one frequency (if successful with the first test).  This is plainly not happening.  One of our staff wrote up a report for an ITU survey on this issue about 5 years ago.  The only traffic we should see these frequencies are:
a)    Distress messages - Subsequent comms on R/T distress or NBDP distress frequencies
b)    Urgency messages- Subsequent comms on R/T or NBDP using frequencies as directed by the originating station in the RX/TX frequency fields.  At the MOC we always use the R/T distress frequencies for our message traffic.
c)    Safety (includes Test & All Station messages). - Subsequent comms as directed by the originating station.

NB: We have noticed that both Korea and Vietnam Coast Radio Stations precede their scheduled Maritime Safety Information broadcasts with a DSC Station call.  GMDSS regulations states that this is not required.
4.  Telecommand 1.  Dependant upon the type of message this field can serve different purposes.  On some messages it will indicate the subsequent mode of communications.  On other times it will serve as a formatting instruction for the message (usually distress acknowledgments and distress relays).  It can also be used for requesting position reports and polling commands.
5.  Telecommand 2 is designed for use in commercial services, so will not be used for messages on the Distress, Urgency and Safety frequencies.  (I can hear the big "yeah right").
Hope you Xmas and New Year went well.
Best wishes to you n yours for the New Year
Cheers
Ditz
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Is there anyone on here with some knowledge of the procedures used on HF
Digital Selective Calling (DSC)?
I've just started decoding this traffic and was wondering about the large
numbers of apparent test messages to and from coast stations.
Like this:
<Selective call to a particular individual station>
Called MMSI station address: ØØ41221ØØ [Coast station: Shanghai MRCC
Shanghai/MRCC China] (China)
Category: Routine
MMSI self-identifier: 412Ø8178Ø [Ship] (China)
Telecommand 1: J3E telephony
Telecommand 2: No information
Neither RX/TX frequencies nor position supplied
Check Sum: OK
Date and time of decoding: 31/12/2Ø1Ø Ø8:12:44
There are occasional obvious distress or urgency calls such as this copied
on 8414.5:
<Selective call to a group of ships in a particular geographical area>
Zone: ØØ°N Side=Ø6°    143°ESide=Ø6°
Category: Urgency
MMSI self-identifier: ØØ5Ø3ØØØ1 [Coast station: Charleville/Wiluna RCC
Australia] (Australia)
Telecommand 1: J3E telephony
Telecommand 2: No information
RX frequency: 8291.Ø KHz    TX frequency: 8291.Ø KHz
Check Sum: OK
Date and time of decoding: 31/12/2Ø1Ø Ø7:51:36
This preceded a PAN PAN voice call by RCC Australia/VIC on 8291kHz about an
overdue dugout canoe.
Does anyone know the purpose of all the other calls with no Telecommand or
RX/TX frequencies specified? Random button presses or do they have a
purpose?
Happy New Year
Andy
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