[TheList] HF DSC traffic

Fri Dec 31 19:15:18 AEDT 2010

Hi all,

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