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Old 27-06-2010, 05:31   #16
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What a bunch of hooey!!! There is no Coast Guard bulletin that says if you don't get an acknowledgment to your emergency DSC transmission, we're not coming to help you. That's like saying if you dial 911 and hang up, the police won't respond. Complete and utter nonsense. In fact, the document you provided a link to says: "there are no DSC false alerts from the Coast Guard watchstander's perspective. Each alert must be investigated."

Everyone reading this thread please be assured if your on the high sea's and send a DSC alert from your M802 and word eventually gets to the Coast Guard, they will initiate search and rescue whether you receive a DSC acknowledgment or not.

Eric
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Old 27-06-2010, 06:23   #17
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And oh by the way, you can make DSC all ships calls and group calls without having to have the receive antenna as there is no digital ACK to these calls. The M802 will switch to the voice channel after making the DSC call and you can continue with your traffic. Even when making an emergency distress call, the radio will switch to the voice channel regardless of a DSC ACK.

Eric
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Old 27-06-2010, 07:01   #18
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Please post more on exactly how and what you used for a wire on your backstay for a DSC receiving antenna.
Thanks,
rdw
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Old 27-06-2010, 07:04   #19
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But for the simple trouble of hooking up a second simple receiving antenna you may know exactly what is going on instead of praying help is coming?
And I guess I would say why not have it. I have not seen anything that says it would hender anything.
rdw
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Old 27-06-2010, 07:34   #20
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No one here is arguing that the DSC receive antenna should not be hooked up. One was arguing that it was "required". This is only true of ships required to carry HF gear under SOLAS, but it does not apply to your "not for hire" pleasure boat.

The original poster was asking about antenna options for DSC receive, not whether to put one up or not.

If you aren't using your backstay as a transmitting antenna, just run a wire from the DSC receive jack on the M802 to the backstay and attach it there. Try it out. If the backstay is grounded at the lower end it might not work so well or it might work fine. Hook your DSC antenna up to your regular transmit/receive jack on the M802. If you can hear static crashes from lightning or other atmospheric noise, your antenna should do service as the DSC receive antenna.
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Old 27-06-2010, 07:50   #21
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There is obviously a great mis-understanding as to how DSC works. When you press the red button on the M802 a digital signal goes out over either the default emergency frequency or one of the other emergency frequencies that you select on your main antenna. Your radio will then switch to the associated voice frequency as will the radio of any ship that has received your DSC call. You then carry on voice communications via your main antenna, NOT THE DSC ANTENNA. If you have a DSC receive antenna, you may get the DSC acknowledgment signal letting you know that your distress signal was received. The only purpose of that receive antenna port and the internal seperate DSC receiver is to monitor the distress, urgency and safety frequencies. All other DSC calls on OTHER frequencies are carried out, both send and receive, via your main antenna as long as you are in DSC watch mode. You should not carry out routine DSC traffic over the distress, urgency and safety frequencies. If you want to do a position request to a friend, you should be doing it over a pre-determined frequency that you both have set in your DSC watch memory. This communication will take place over your main antenna, not your DSC antenna. It's all there in the manual. RTFM

Eric
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Old 27-06-2010, 10:37   #22
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DSC protocol is mostly misunderstood, even by the best sailors, Eric. But for your benefit and your lack of understanding of HF DSC transmission functions:
U.S. Coast Guard Navigation Center - HF Distress and Safety Watchkeeping Schedule ~bottom of page.
"HF DIGITAL SELECTIVE CALLING"
"Coast Guard will normally respond to DSC test calls if acknowledgment is requested. Reports of uncancelled or unacknowledged inadvertently transmitted distress calls will be forwarded to the Federal Communications Commission."
This applies to test DSC call and emergency calls that are NOT acknowledged by your DSC radio; which it can't do without receiving capability.
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Old 27-06-2010, 10:50   #24
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Please post more on exactly how and what you used for a wire on your backstay for a DSC receiving antenna.
Thanks,
rdw
The wire has to be at least 50", but stay away from 1/2 sizes or odd numbers.
The kit I tried was the GAM/McKim Split Lead Antenna.
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Old 27-06-2010, 11:13   #25
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It is my understanding that if you do not have a DSC receiving antenna and do a distress call, if another party contacts you buy voice (there by occupying your send and receive functions) you will be unable to monitor and receive information that the Coast Guard might send, i.e. acknowledgement.
Is that not correct?
rdw
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Old 27-06-2010, 11:51   #26
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Originally Posted by Seahunter View Post
"Coast Guard will normally respond to DSC test calls if acknowledgment is requested. Reports of uncancelled or unacknowledged inadvertently transmitted distress calls will be forwarded to the Federal Communications Commission."
This applies to test DSC call and emergency calls that are NOT acknowledged by your DSC radio; which it can't do without receiving capability.
Wow Seahunter, you are so wrong on this it is ridiculous. The Coast Guard nor anyone else can know if my radio has received an acknowledgment. If you send an emergency distress DSC call and it is ultimately received by the Coast Guard, they will come to your rescue. If they then determine the call was inadvertent or an otherwise false distress call, they will report you to the FCC. That's what that means.

Eric
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Old 27-06-2010, 12:45   #27
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It is my understanding that if you do not have a DSC receiving antenna and do a distress call, if another party contacts you buy voice (there by occupying your send and receive functions) you will be unable to monitor and receive information that the Coast Guard might send, i.e. acknowledgement.
Is that not correct?
rdw
You will not receive the DSC ACK. All that does is stop your radio from transmitting the DSC alert and lets you know that it was received. You should already know that once you establish voice comms, assuming you have time for that, and then you should cancel the DSC transmission manually. Just because a coast station has received your DSC distress call and has sent a DSC ACK doesn't neccessarily mean you will receive it because of propagation and antenna's. If the Coast Guard has received your distress alert and has your position and then doesn't hear another peep out of you, they are on their way no matter if your radio has received an ACK or is now sitting on the bottom of the ocean. If they arrive and find you sipping wine and having a laugh, you will be in BIG trouble with the FCC.

The main function of DSC is to automate the steps neccessary to transmit an emergency distress call. Press the red button for 5 seconds and your MMSI and position will be automatically transmitted and if it is received by the Coast Guard you WILL NOT have to wait for an ACK or even establish voice comms in order for SAR to be initiated.

Eric
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Old 27-06-2010, 12:45   #28
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The only thing is that if your HF radio does not receive an ACK, it will keep sending out a DSC distress every 4 minutes or so until you hit the CANCEL/CALL button. When it does receive an ACK, it will cease sending the DSC distress call, but you still have to hit CANCEL/CALL to turn off the loud beeping from the M802. Your not receiving an ACK will certainly not prevent the mobilization of rescue resources.

You could get in trouble "with the FCC" if someone accidentally hits the Distress button and the inadvertent DSC call is not cancelled manually or by receiving an ACK. it would be hard to ignore the blaring from the M802, however.
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Old 27-06-2010, 13:11   #29
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I don't see how it could be done accidently since you have to open the spring loaded door and press and hold the button for 5 seconds

Eric
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Old 27-06-2010, 17:18   #30
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Quote:
Originally Posted by RDW View Post
It is my understanding that if you do not have a DSC receiving antenna and do a distress call, if another party contacts you buy voice (there by occupying your send and receive functions) you will be unable to monitor and receive information that the Coast Guard might send, i.e. acknowledgement.
Is that not correct?
rdw
RDW, I wasn't exactly sure, so I tried it. The test went out as a packet burst and did not effect the voice. The AK also came back as a packet burst and was noticed as a bit of static as well as the DSC response from the radio. That's it.

Eric, when the AK comes in the 802 responds in kind, that's how they know. As for the bulletin let it mean to what you want it to mean and I won't be holding my breath waiting for you to figure it out. If you're so much in denial when reading from the USCG site, my guess is your the kind of person who doesn't wear a life jacket as well.
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