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Old 26-02-2013, 11:01   #31
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Re: ICOM M802 DSC antenna?

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While you are correct that if you get a voice acknowledgement, you can stop your display the automated frequency change by pressing and holding the Call Cancel button, a Distress Acknowledgement contains the frequency they want to talk to you on. If you have already (automatically) shifted to the next frequency when they acknowledge the shore station acknowledges via voice you could easily miss the acknowledgement. If your system will antenna is adequate to receive the DSC Acknowledgement, you will be directed automatically, by pressing enter to the Traffic Frequency.
TLSparks, It matters not, you only get a voice Ack as a response to a Voice Mayday. Normally the CG radio acks the distress, the radio does not retune to a new frequency as it is a requirement that you follow up a DSC Distress Immediately with a Mayday, ( And it is that which will be acknowledge by voice).

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Old 26-02-2013, 15:23   #32
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Re: ICOM M802 DSC antenna?

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Originally Posted by ka4wja View Post
As for others comments on not needing to receive DSC calls from 1000's of miles away, you all DO have a point....but since I'm a "radio nut" and since this ability has not been detrimental to me (nor a bother to me or crew), and since it is possible that someday I might wish for this capability, I figure why not!!!
The shrieking alarm from the 802 would wake the off watch. I disconnected the masthead DSC antenna and stuck some wire in the DSC antenna jack.

It hasn't been a problem on the US side of the Atlantic, but the darn alarm was sounding a couple of times a night on the EU side.
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Old 26-02-2013, 18:52   #33
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Re: ICOM M802 DSC antenna?

Interesting. What is your source. Send me a link if you could I have the international procedure posted on my site last year and it sounds like I need to change it. COuld be why I have not heard Relays this year.

For Cruisers way off shore I thought it was a great deal, but I can see since GMDSS was not really developed for cruisers that may not mater much.

Terry

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Actually GMDSS procedure now is that Distress Relay is not to be used. Relays are to communicated by voice , or at very best using a standard DSC call to a HF/MF coastguard station. The automated or semi-automated use of DSC relays is being removed and abandoned as it has produced vast quantities of DSC alerts bubbling up from one source.

SO the rules is relay all distress alerts by voice
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Old 26-02-2013, 18:55   #34
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Re: ICOM M802 DSC antenna?

You kind of missed the point. A Distress Acknowledgement is sent by the shore station to you when you send out a distress. It tells you what frequency they want to talk on. For the folks headed to the South Pacific here in Puerto Vallarta, 3000 mile is nothing.

Terry

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Agree. I can make 6 knots in most conditions, 8 and a bit when everything is perfect. I can't help someone more than a few hundred miles away and even then there is almost always someone better positioned.

If the antenna system on my boat hears a distress call there WILL be others better configured on commercial and government platforms that hear too.

Do I listen? Of course! Will I help if I can? Of course! Do I want to hear Med DSC traffic when I'm between Newport and Bermuda? No.
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Old 26-02-2013, 19:14   #35
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Re: ICOM M802 DSC antenna?

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Originally Posted by Tip View Post
Any thoughts on using a shroud as the DSC antenna? I have rather easy access to the chainplates inside the boat and am thinking of hooking up to this. Does the shroud need to be insulated for any reason? I'm using an insulated backstay antenna.
It's worth a try and might work well enough for you. The DSC antenna is for receive only (no transmit).

If your mast were spruce, it might work even better, but I believe the Hans Christian's have aluminum masts. Still, plug a wire from the chainplate into the center pin of your transceiver and see what you hear. DO NOT TRY TO TUNE OR TRANSMIT. Try listening on international broadcast frequencies, air traffic control frequencies, ham net frequencies, WWV, etc.). Then swap antennas and plug in your backstay antenna and see what difference in signal strength there might be.

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Old 26-02-2013, 19:14   #36
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Re: ICOM M802 DSC antenna?

Sorry John if I miss read your posting. An insulated stay is perfect. Wish I had an extra.

I have been doing a lot of thinking about going to a grounded stay. I need to do some more calculations, but I have been thinking that if you run the center conductor through a 0.002 microfarad cap (in series), it would isolate the DC component from the input to the radio and have minimal impact on the input to the radio. If connected up the stay a bit it would result in two antennas grounded at each end.

Worth thinking about. Any Ideas?

The Distress ACKs I have received were public, I was not a part of the call in any way.

The distance 1000+ distance is primarily based around my friends here in Puerto Vallarta heading to the South Pacific. Unfortunately the GMDSS system may be changing based on another comment in the forum and not for the best for cruisers. It is a warming thought that even if my radio does not reach a SAR station from way off shore that someone else will relay. I do understand why the commercial vessels would not want to dod it. Since we spend our time in Mexico and the Sea of Cortez it does not effect me either, but I am interested to make sure my friends and other cruisers stay safe on long passages.



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Originally Posted by ka4wja View Post
Terry,
I think I detailed my set-up quite well in the posts above....(~24' insulated shroud as my DSC-rec and WeFax-rec antenna...)
And, I made indiv calls to both WLO and NMN, and a couple to large ships (QM2, etc.), and a few to other pleasure boats w/ M-802's.....
Sorry, if I didn't detail that clearly...


When I've received "DSC-Distress" calls (only 3 in the past 8+ years) and one "Distress-Relay" call (while in port in Horta, in 2007), I've hit cancel right away to spot the deafening alarm, and switched immediately to the voice ("traffic") channel, so I've never waited to see if I'd receive a "Distress ACK"......

I always figured that the "Distress ACK' was directed at the specific MMSI that sent the "Distress" call in the first place....and that's why I never waited to see if I'd receive one.....now I know different...
So, Terry, thanks for the new info!!!

~~~

As for others comments on not needing to receive DSC calls from 1000's of miles away, you all DO have a point....but since I'm a "radio nut" and since this ability has not been detrimental to me (nor a bother to me or crew), and since it is possible that someday I might wish for this capability, I figure why not!!!
And, in my case, I use this same antenna (using a simple coax "Tee") to feed both my M-802 DSC-rec antenna jack, AND my Furuno FAX-408 WeFax-rec (and my old Alden MarineFaxIV before that)......and it works GREAT for both applications....


Fair winds to all....

John
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Old 26-02-2013, 19:21   #37
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Originally Posted by TLSparks View Post
You kind of missed the point. A Distress Acknowledgement is sent by the shore station to you when you send out a distress. It tells you what frequency they want to talk on. For the folks headed to the South Pacific here in Puerto Vallarta, 3000 mile is nothing.

Terry
That is not the purpose of an ACK and in fact if following protocol the CG radio station does not initiate voice as a result of distress ACK. , you the sender follow up distress alerts with a voice mayday and its to that call that the CG station responds many radios do not and know should not retune or reception of a distress ACK as you could be in the middle of a voice mayday

The primary purpose of a distress ACk is to ack is to acknowledge to all listening vessels that a land based radio station has received the distress alert and therefore the auto send can be cancelled.

Am awful lo o f people need to read up on GMDSS procedures. The old SOLAS procedures are gone folks
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Old 26-02-2013, 19:28   #38
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"The distance 1000+ distance is primarily based around my friends here in Puerto Vallarta heading to the South Pacific. Unfortunately the GMDSS system may be changing based on another comment in the forum and not for the best for cruisers. It is a warming thought that even if my radio does not reach a SAR station from way off shore that someone else will relay. I do understand why the commercial vessels would not want to dod it. Since we spend our time in Mexico and the Sea of Cortez it does not effect me either, but I am interested to make sure my friends and other cruisers stay safe on long passages."

TL.

Its a Fundemental requirement of GMDSS that your distress equipment should reach a shore station, not another ship. Hence the specifications for the various sea areas. That's is because under GMDSS rescue asset coordination no longer is decided by ships in the vicinity but by the designated MRCC .

Hence relaying is really only a stopgap feature in the event that for some reason you cannot reach a shore station.

In HF in particular auto or semi auto distress relaying using a DSC mayday relay has causes NxN style distress alert flooding often with distress alerts being relayed around the globe triggering multiple MRCC in an attempt to generate distress ACKs.

Hence recently the ITU has advised that DSC selective call or just voice be used to relay on a distress alert

Dave
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Old 26-02-2013, 19:53   #39
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Re: ICOM M802 DSC antenna?

I guess I can not disagree with what you stated, but that is not the point I was making.

You had stated that at 6-8 knot you could not help anyone and a 1000 miles away and my point was I was just wanting to receive an ACK from 1000 miles away in response to my Distress call.

The ACK has 2 functions (from what I have seen in real life), it tells everyone someone and who is handling the problem and it tells the distress vessel they have received the call and to meet that station on frequency X via voice. Pressing Enter on the 802 takes you to that frequency. Where I am I going wrong here or can we agree on this point>

Regards
Terry

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Originally Posted by goboatingnow View Post
That is not the purpose of an ACK and in fact if following protocol the CG radio station does not initiate voice as a result of distress ACK. , you the sender follow up distress alerts with a voice mayday and its to that call that the CG station responds many radios do not and know should not retune or reception of a distress ACK as you could be in the middle of a voice mayday

The primary purpose of a distress ACk is to ack is to acknowledge to all listening vessels that a land based radio station has received the distress alert and therefore the auto send can be cancelled.

Am awful lo o f people need to read up on GMDSS procedures. The old SOLAS procedures are gone folks
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Old 26-02-2013, 20:07   #40
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Re: ICOM M802 DSC antenna?

That is true Dave and I hope I did not state anything different.
The way it works is when you press the red button it sends a DSC distress on 8MHZ, they it shifts to the voice hailing 8MHz frequency and allows the operator to do a voice Mayday (the display says waiting for ACK so if the operator is not aware of what just happended they may not even do a May Day call). After about ~3+ minutes the M802 shifts, automatically to 12MHz DSC frequency and sends the message again. Again it shifts to the 12 MHz voice hailing. etc for 16 MHz then 2 MHz then 6 MHz, then back to 8 MHz. It will keep doing this until an incoming ACK comes in or the operator presses and holds "Cancel/Call" button.

Now the reason I bring this up is, if the Coast Guard does not resond to the voice May Day within the ~3 minutes, the Distress operator's radio will be on the next frequency. If they can receive the Distress ACK, from the shore station responding, it will tell them what station to go to for voice communications within the ACK. If you do not receive the ACK because of a substandard antenna, it could add additional time to the process. If they receive the ACK, pressing "ENT" will take them to the channel as specified within the ACK and the Coast Guard should be there waiting.

Regards

Terry

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Originally Posted by goboatingnow View Post
TLSparks, It matters not, you only get a voice Ack as a response to a Voice Mayday. Normally the CG radio acks the distress, the radio does not retune to a new frequency as it is a requirement that you follow up a DSC Distress Immediately with a Mayday, ( And it is that which will be acknowledge by voice).

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Old 26-02-2013, 20:39   #41
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[QUOTE ]Now the reason I bring this up is, if the Coast Guard does not resond to the voice May Day within the ~3 minutes, the Distress operator's radio will be on the next frequency. If they can receive the Distress ACK, from the shore station responding, it will tell them what station to go to for voice communications within the ACK. If you do not receive the ACK because of a substandard antenna, it could add additional time to the process. If they receive the ACK, pressing "ENT" will take them to the channel as specified within the ACK and the Coast Guard should be there waiting.[/QUOTE]

This is exactly my point and the GMDSS procedure is different.

DSC ACK is merely to acknowledge receipt of the distress alert ( itself a DSC signal ) it in not a way , HF signals that the CG is waiting on any frequency , as the CG radio cannot actually know what frequency you can get through on , until you actually try. So while the radio expects you to make a voice call on the HF frequencies , its up to the voice procedure to determine what actual frequency gets used, as the CG is listening on all four emergency frequencies. Hence you can make the voice call on any emergency HF frequency irrespective of the DSC alerting frequency being used, this is because digital signals can get through when voice can't , so you could get an alert and ack , yet not be able to issue the mayday voice and receive a response on that freq.

In fact in the most recent ITU updates , all auto switching of the radios are being disabled , as operators have complained that acknowledgment of alerts has forced channel changes while they where in the middle of a voice procedure. ( its also very error prone to rely on the specific radio for the procedure, icom in particular made many mistakes in getting their 802 HF radios to meet MDSS protocols, I've seen icom HF class D radios yet equipped with class A distress ACK , which they shouldn't have.

Hence its not terribly important that you never receive a DSC distress ACk, the voice procedure covers it.

Dave
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Old 27-02-2013, 04:03   #42
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Re: ICOM M802 DSC antenna?

Dave, That is interesting and will send me off doing research again so I have the latest info on hand.

Two points though I would like to make.
1. For us cruisers with IC M802 transceivers, no one is modifying our units to stop them from automatically change to the next frequency.
2. When a Distress ACK comes out it includes the voice frequency they want to talk on which is probably based on what frequency band they received the DSC call.

If this is all changing, it is unfortunate for us with radios from the prior process. Commercial ships will probably just buy a new radio for major changes. Not going to happen for cruisers.

Regards
Terry

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Originally Posted by goboatingnow View Post
[QUOTE ]Now the reason I bring this up is, if the Coast Guard does not resond to the voice May Day within the ~3 minutes, the Distress operator's radio will be on the next frequency. If they can receive the Distress ACK, from the shore station responding, it will tell them what station to go to for voice communications within the ACK. If you do not receive the ACK because of a substandard antenna, it could add additional time to the process. If they receive the ACK, pressing "ENT" will take them to the channel as specified within the ACK and the Coast Guard should be there waiting.
This is exactly my point and the GMDSS procedure is different.

DSC ACK is merely to acknowledge receipt of the distress alert ( itself a DSC signal ) it in not a way , HF signals that the CG is waiting on any frequency , as the CG radio cannot actually know what frequency you can get through on , until you actually try. So while the radio expects you to make a voice call on the HF frequencies , its up to the voice procedure to determine what actual frequency gets used, as the CG is listening on all four emergency frequencies. Hence you can make the voice call on any emergency HF frequency irrespective of the DSC alerting frequency being used, this is because digital signals can get through when voice can't , so you could get an alert and ack , yet not be able to issue the mayday voice and receive a response on that freq.

In fact in the most recent ITU updates , all auto switching of the radios are being disabled , as operators have complained that acknowledgment of alerts has forced channel changes while they where in the middle of a voice procedure. ( its also very error prone to rely on the specific radio for the procedure, icom in particular made many mistakes in getting their 802 HF radios to meet MDSS protocols, I've seen icom HF class D radios yet equipped with class A distress ACK , which they shouldn't have.

Hence its not terribly important that you never receive a DSC distress ACk, the voice procedure covers it.

Dave[/QUOTE]
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Old 27-02-2013, 04:09   #43
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Re: ICOM M802 DSC antenna?

That is interesting. Why did you stick some wire in the DSC antenna jack if you did not want to hear the alarms?

Regards
Terry

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The shrieking alarm from the 802 would wake the off watch. I disconnected the masthead DSC antenna and stuck some wire in the DSC antenna jack.

It hasn't been a problem on the US side of the Atlantic, but the darn alarm was sounding a couple of times a night on the EU side.
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Old 27-02-2013, 05:04   #44
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Re: ICOM M802 DSC antenna?

Dave I am going to need some help. You stated that DSC Distress Relays had been eliminated. I can not seem to find that information in the internet, In fact just the opposite. An issue at the ITU is how to ACK to all the Distress Relays. CG does not seem to have anything posted since 1999, also supporting relays. Australia instructions are basically the same as I have posted on my site.

So do you have access to something not on the net that should be?

Regards
Terry

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Originally Posted by goboatingnow View Post
In fact in the most recent ITU updates , all auto switching of the radios are being disabled , as operators have complained that acknowledgment of alerts has forced channel changes while they where in the middle of a voice procedure. ( its also very error prone to rely on the specific radio for the procedure, icom in particular made many mistakes in getting their 802 HF radios to meet MDSS protocols, I've seen icom HF class D radios yet equipped with class A distress ACK , which they shouldn't have.

Hence its not terribly important that you never receive a DSC distress ACk, the voice procedure covers it.

Dave
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Old 28-02-2013, 07:50   #45
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Re: ICOM M802 DSC antenna?

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Agree. I can make 6 knots in most conditions, 8 and a bit when everything is perfect. I can't help someone more than a few hundred miles away and even then there is almost always someone better positioned.
You kind of missed the point. A Distress Acknowledgement is sent by the shore station to you when you send out a distress. It tells you what frequency they want to talk on. For the folks headed to the South Pacific here in Puerto Vallarta, 3000 mile is nothing.
Not relevant. If you send a DSC Distress call (main transmitter) the Ack will be picked up by the main receiver, not the DSC receiver unless I completely misunderstand the logic path in the Icom radio.

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That is interesting. Why did you stick some wire in the DSC antenna jack if you did not want to hear the alarms?
Because I did want to hear a DSC alert if it was close enough for me to help, I just didn't want to hear them from thousands of miles away.

I now have an inline low gain low noise pre-amp in the DSC receive circuit. With it powered up I do hear DSC through the DSC receiver from great distances. With it turned off it acts as an attenuator and in most conditions I only hear DSC alerts within about 500 miles.
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