strange that all merchant ships utilise this technology, yet its not monitored on shore? I don't buy it... I've seen the Vicky Pt VMR using the icom dsc enabled units so I presume they would have a dsc unit number and as Lloyd says they must therefore be monitoring it.Originally Posted by Taroona
regardless. if I ever go down and activate the dsc function I know my alert will be picked up by monitoring vessels and relayed to help onshore.
imagine your boat goes down so fast you literally can't take the time to send out a verbal mayday with your position? You hit the dsc alert button, get your jacket on and know that help is on the way.
the point isn't that the technology is 'useless' because 'avcg or vmr don't all monitor it' - if you did the course and have your license you will know that by sending out a dsc alert it repeats over and over to all vessels who are obliged to respond. it literally will not stop the alarm on a merchant vessel until the message is read.
if you don't want to fork out for it thats fine - everyone has a choice in life. as said earlier, the course and subsequent license teaches a multitude of things that every person can get something out of - its not just 'how to speak on your radio'.
having dsc is that extra peace of mind for me and didn't cost much at all when you think about it. its another set of eyes and ears out there...
After doing the course with subzero last year some time it opened my eyes to about how I little I knew about the correct use of a VHF set at the time. Thats not to say I know everthing now.
My radio is always on 16 and my GPS is connected to it in case I need to use the DSC feature.
My initial response was to the list that subzero came out with listing all the stations that monitor DSC. So I sent an email off the AVCG and VMR. Haven't heard from VMR yet.
That would be a very dangerous assumption to make Mik.
The data packets are extremely small and a whole host of issues could come into play here.
Please dont think that I am knocking the system, I'm not, I'm all for enhanced safety at sea, especially for the weekend wonders like you and I.
I also spoke to a mate who is a skipper of an east coast trawler, and he has heard of DSC but doesnt know much about it.
I reckon I'll take whatever I can get at the time!!
Yes, that is true and a good point. I was specifically talking about the silence periods, and forgot that area.
Jeremy
"The underlying spirit of angling is that the skill of the angler is pitted against the instinct and strength of the fish and the latter is entitled to an even chance for it's life."
(Quotation from the rules of the Tuna Club Avalon, Santa Catalina, U.S.A.)
Apathy is the enemy
Please everyone, actually phone the location to confirm they really do have the DSC in operation. Two years ago I rang a few of those locations published on the net ( check subzero's postings above) and the operator at the location had no clue what I was talking about.
Just look at the disclaimer AMSA place on the web page:
Note: AMSA provides access to the information contained in this database free of charge. AMSA does not warrant the accuracy or completeness of the information and accepts no responsibility or liability whatsoever for any errors, defects, faults or omissions in the information. No person should act or fail to act on the basis of the information and persons should make their own inquiries about its accuracy. For further information, please contact AMSA on 1800 641 792.
5 P's - Proper Planning Prevents Poor Performance
It's good Taroona made the effort to check before assuming and we all know what ass-u-me means!!
Re: Is a VHF Radio licence really necessary
Thanks Gaz:
FYI everyone else..
http://www.ausfish.com.au/vforum/sho...d.php?t=126495
next course on April 13th
Peter
Once the MMSI number is programmed into your radio how you go about testing it to see if it works!!!!!!!!!!
Polling.
Set it up and ask your mate that also has DSC whether or not he can see you.
Found some great info here:
http://continuouswave.com/ubb/Forum6/HTML/000726.html
A recent innovation in VHF Marine Radio Band radio communication has been the introduction of Digital Selective Calling (DSC). This function allows one radio to place a selective call to a particular other radio, and to transmit and receive digital information from that particular other radio. The design of DSC allows short text messages and even remote printing to occur. However, in small recreational vessels, most of the DSC capability is limited to Class-D, which implements some basic safety and position polling features. VHF Marine Radios which have Class-D Digital Selective Calling (DSC) capabilities include a function where the radio can transmit the vessel's position to other vessels. Generally the radio does not have a means of determining the vessel position itself, and the radio requires that it be connected to a source of NMEA-0183 data that will provide the vessel position information. Typically a radio's NEMA-0183 INPUT is connected to an NMEA-0183 OUTPUT from the vessel's GPS receiver. The GPS is configured to transmit the proper data on this connection, and the radio listens to the data stream.
The vessel's position information is not transmitted continuously. The most common use is the transmission of the vessel position when the DISTRESS button has been activated. In that situation, the radio sends the vessel's position as part of the distress notification message which is transmitted. In addition to the vessels' position, the radio will also transmit the age of the position information and the accuracy of the data. This is a good design feature, as the vessel's GPS may have been disabled and might have old data on its output. Others who receive the data can assess its value based on its age and accuracy. The distress message is a broadcast message and will be delivered to all vessels with a DSC radio which receive the signal. It is somewhat ironic that the Digital SELECTIVE Calling feature is being used here in its most basic application as a non-selective or broadcast transmission.
This functionality and integration of the vessel's radio and GPS are the most basic implementation of vessel position polling. However, the design of DSC allows for other uses of this information in non-emergency situations. For example, a vessel may transmit its position information to a particular other vessel. In this way, two vessels may privately exchange their position information. In order for this to be done, the DSC radio must also have the ability to receive DSC messages and relay their contents on an NMEA-0183 OUTPUT. Typically this data would be sent to a Chart plotter device. (The chart plotter may integrated with a GPS receiver or could be a separate display device.) The chart plotter would then plot the position of the vessel on its display.
Not all VHF Marine Band radios have the ability to both send and receive DSC data. Typically, this feature is only offered on the more expensive models of DSC radios. Look for an indication that a particular radio has DSC position polling reception.
Also, not all chart plotters have the capability to display or plot the position of other vessels. Look for an indication that a particular chart plotter has an NMEA-0183 INPUT and will plot vessel position data it receives.
Let us assume we have two vessels which have the proper radio and chart plotters aboard, and they have been properly interconnected. What else is needed for the two vessels to exchange position data?
The first requirement is that the vessels have registered their DSC radios and obtained an Maritime Mobile Service Identity (MMSI). The MMSI is a unique registration number which is programmed into the radio. This identifier is used when the radio transmits (to identify the source of the transmission) and when the radio listens (to identify which messages are intended for that radio). Let's assume that both skippers have properly registered their radios and have obtained an MMSI.
Next, the MMSI must be programmed into the radio. Typically there is a special sequence for entering an MMSI into a radio. Be careful when programming a radio, as most devices do not permit the MMSI to be changed once programmed, or may only allow one change after initial programming! (In the U.S. there are federal regulations which require all radios sold to only allow the MMSI to be programmed twice by the user. This is probably to prevent capricious changes in a vessel's MMSI.)
Now the two skippers must exchange each other's MMSI in advance. In order to contact another vessel using DSC, you have to know that vessel's MMSI.
Finally, the MMSI of the other vessel has to be entered into the calling vessel's radio. The typical DCS radio on a recreational vessel does not have a full numeric keyboard for entering data, and this can make entry of the MMSI somewhat tedious to accomplish, particularly at sea. Thus it will most likely be necessary to pre-program the MMSI of the other vessel into your radio before leaving the dock. The typical process on a radio without a numeric keypad will probably involve a lot of additional keystrokes and button press combinations.
Now we are ready for our two vessels to exchange position information. Let's review the preparations needed on both vessels:
--DSC radio with input for position transmission
--DSC radio with output for received position
--MMSI registration of vessel
--MMSI programmed into vessel's radio
--GPS
--GPS output connected to radio input
--Chart plotter with input for external position plotting
--Chart plotter connected to radio
--Other vessel's MMSI known
--Other vessel's MMSI programmed into radio
And one final factor: both vessels have to be within radio range of each other! For most small recreational boats with antenna heights around 6-feet, this means the two vessels will have to be within about 8-miles of one another. Let's call them vessel-A and vessel-B to keep track.
Ready? Let's exchange position data. The procedure is as follows:
Vessel-a sends a POSITION REQUEST CALL to vessel-B. We'll use an ICOM radio as a typical radio and demonstrate the process:
TRANSMITTING A POSITION REQUEST CALL:
--Push DSC•POS to enter the DSC menu;
--Push [↑] or [↓] to select POS REQuest
--Push DSC•POS
--Push [↑] or [↓] to select the desired pre-programmed individual address;
--Push DSC•POS to enter the standby condition for Position Request Call; (channel 70 is selected on the radio and READY appears at the channel comment indicator;
--Push DSC•POS to transmit the Position Request call;
--After the Position Request call has been transmitted, the following indication is displayed: WAIT ACk
--Push any key to exit.
OK, our message has been sent. Assuming vessel-B is within radio range and is listening, the following will occur at that end (again assuming the use of a similar ICOM radio):
RECEIVING A POSITION REQUEST CALL
While monitoring Channel 70 and a Position Request call is received on vessel-B:
--DSC appears and RCV POS REQUEST scrolls at the channel comment indicator;
--the BEEP sounds for two minutes; press any key to stop the beep;
--Push DSC•POS to reply to the call; push any other key to ignore.
Back at vessel-A, he is now receving a reply to his request:
RECEIVING A POSITION REQUEST REPLY CALL
While monitor Channel 70 and a Position Request Reply call is received:
--DSC and POS REPLY appears in the display;
--the lattitude and longitude of vessel-B appear in the channel comment indicator and scroll across, showing first the latitude coordinate and then the longitude coordinate;
--the BEEP sounds for two minutes; press any key to stop the beep;
--Push DSC•POS to reply to the call; push any other key to ignore.
--the BEEP sounds for two minutes; press any key to stop the beep;
If vessel-A has his chart plotter turned on, the position of vessel-B should be shown. Repeat all of the above to exchange positions in the other direction.
Fishes 14 nm out and won't be replacing his analogue an epirb at the end of the year?. Got a VHF and no licence. Yep go and buy new fishing gear I am sure your mobile phone will work should you need communication to the rescue group your a member of. Safe boating everyone
Last edited by hondaguy; 13-03-2008 at 10:41 AM.
Got my MMSI number and programmed into VHF
Then got on the phone to see if I could test it to
1/. Vic point VMR.......... No
2/. Tried Raby bay......No
3/.Tried Brisbane CG...No Any way the AVCG had already said No, but thought I'd try anyway. The guy there answering the phone didn't even know what DSC was.
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