[TheList] HF DSC

Sun Jan 2 14:04:33 AEDT 2011

Hi Ditz,

“I guess you wouldn't remember me” 
 I certainly do – as I recall you had a
reasonable result on the pokies at the Sky City Casino during the after
course function!
Good to hear from you again, and many thanks for the insight into the
mysteries of DSC. I suspected that all that traffic could not possibly be
all legit!!

All the best for the New Year

Andy

From: thelist-bounces at radiowiki.org.nz
[mailto:thelist-bounces at radiowiki.org.nz] On Behalf Of dpowell
Sent: Sunday, 2 January 2011 2:41 p.m.
To: thelist
Subject: [TheList] HF DSC

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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