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DSC hook-up question

Old 01-09-2003, 06:28 PM
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Default DSC hook-up question

I hooked the nmea output of my RL70CRC to the DSC input on my VHF. Works great. But, if I do not have the RL70 'on', no signal will go to the VHF.

Since I am often anchored for long period off shore, I don't want to leave all the electronics on in order to conserve power. Will it work to tap into the output of the GPS 120 antenna? The current draw of the GPS antenna is minimal.

Scott
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Old 01-10-2003, 04:10 AM
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Default DSC hook-up question

Scott,

Your VHF cannot be connected to your GPS antenna and obtain your position. The GPS must decode the signals and determine your position, then send that information to the VHF.

You can buy a cheap handheld and connect it if you want position information, or just put your radar in standby mode and leave your gps on.

Casey
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Old 01-10-2003, 09:31 AM
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Default DSC hook-up question

Or, just turn on the GPS unit when things start getting interesting (rough seas, bad weather...) and you think there is a possibilty of a problem. IT doesn't take long (about 10 seconds) for the GPS signal to come on and be sent to the VHF.

By the way, I find that my GPS antenna (the Raymarine WAAS 120) seems to use quite a bit of power. If I leave it on overnight, it will almost drain a battery completely. I had mine powered dirctly off a power terminal that was on whenever the battery switches were left on, and that killed my batt's once. I've have since moved it to a switched circuit I can control. I originally assumed that the GPS antenna was only "on" drawing power when the Screen was on, but that is not true. Stupid, but not true.

Birdman, Capt of
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Old 01-10-2003, 12:02 PM
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Default DSC hook-up question

I was under the impression that the Raymarine waas 120 was in fact a GPS receiver, not just an antenna. The manual shows a NMEA/Seatalk output directly from the wires from the antenna head.

Does this signal from the Raymarine 120 waas unit need to be further decoded through the RL70 before being a usable signal for the VHF?

Bird, I learned the GPS waas 120 current draw lesson too!

Scott
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Old 01-10-2003, 12:24 PM
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Default DSC hook-up question

Interesting. I just checked the Raymarine web site and the NEMA sentences output are listed from the 120. It looks like it does output your position information. Check the output sentences in your 120 manual with the input sentences of your VHF and see if they are compatable. If so, it should work.

Casey
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Old 01-10-2003, 02:50 PM
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Default DSC hook-up question

Thanks. I'll try it tonight.

Scott
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Old 01-10-2003, 08:19 PM
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Default DSC hook-up question

As I was looking through the documentation, it’s not even installed yet, it seems that the antenna has a built DGPS sensor or decoder. This is probably the reason for the Seatalk NMEA interface. The antenna would still work normally without it and pickup the satellites but it wouldn't perform the differential correction.

This DGPS decoder needs to draw power from somewhere. The reason this is external and not built in as on some units is that the GPS signal can be sent around the Seatalk buss so secondary displays or interfaces can pickup the signal. Otherwise if it went direct to the unit it would need an output to the next unit like a daisy chain. So unless your VHS is interfaced into the Seatalk buss you will not receive the GPS data.
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Old 01-11-2003, 12:54 PM
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Default DSC hook-up question

Well, I gave it a shot. I did not get the DSC to work on the VHF by hooking directly to the Seatalk output of the SPS 120. In addition, it would cause the plotter to lose the fix. Sooo, it appears that I will need to have the RL70 on in order to have the position info on the VHF. Hey..... I just added another reason to get a new Mac Daddy EPIRB... yea....what if the RL70 fails....no DSC... gotta have backup saftey. Need a new EPIRB w/gps.
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Old 01-11-2003, 07:38 PM
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Default DSC hook-up question

If you go offshore I would get the EPRIB anyway. The coast guard still does not have the equipment in place to respond to DSC signals. Last I heard it was still going to be a couple of years. That doesn't mean that the DSC feature is useless as other DSC enabled VHFs on other vessels will still get the "All Vessels" broadcast and can respond or hail a maday for you after it picks up your position. Not sure about this but I also heard something about Maritel being able to recive your DSC distress signal if you subscribe to their Ship to Shore service.
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Old 01-12-2003, 08:36 AM
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Default DSC hook-up question

This brings up a question I've been meaning to ask.

On my Icom m502, one of the dsc distress modes is EPIRB. Does that mean it sends out the equive of a 406 epirb signal (on 406)? The user manual is useless, and I dread talking with ICOM support.

Just curious - the feature isn't all together useful because you have to key it in through the menus, and if you need it - well, you probably don't have time, but it did raise an eyebrow.

** sigh **
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Old 01-12-2003, 10:40 AM
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Default DSC hook-up question

You did supply power to the antenna right? It normally gets it from the GPS.

DOH!!
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Old 01-12-2003, 10:56 PM
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Default DSC hook-up question

. . . that is a feature I don't understand either. I've done a little research on DSC lately and I don't recall reading anything about integration of EPIRBs and DSC radios . . . also, I recently bought (not yet installed) the latest Simrad vhf that is a full function DSC machine with secondary ch70 receiver/transmitter, etc. (like the Icom 602) and there is nothing mentioned in the manual about broadcasting EPIRB data. I'm pretty sure the GMDSS protocols keep these two systems separate. Only thing I can think of is perhaps a GPS EPIRB might be able to provide location coordinates to the radio??


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Old 01-13-2003, 07:33 AM
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Default DSC hook-up question

Just as a follow up.

The 120 comes in 2 versions. One that outputs Seatalk, which is raymarine language, and one that outputs NMEA sentences. If you have the Sea Talk version, I am not surprised that it did not work. The VHF will only be able to read NMEA sentences, not the Sea Talk. Unfortunatly you have to choose which version you want when you buy it.

Casey
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Old 01-13-2003, 09:15 AM
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Default DSC hook-up question

Raymarine makes an interface box to convert Seatalk to NMEA and other stuff. Don't know the order number but here is the manual:

http://www.raymarine.com/raymarine/S...81166_3www.pdf

Bill Smith
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Old 01-13-2003, 05:09 PM
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Default DSC hook-up question

CaseyP

You are right. My antenna is the Seatalk version. I am going to look into the nmea conversion box that Bill mentioned in his post.

I will post where I find the best price. Thanks to all for your help.

Scott
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Old 01-13-2003, 05:37 PM
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Default DSC hook-up question

just a thought, but for the price of that converter boxc you could probably buy a backup gps with it's own antenna. Maybe something along the lines of a garmin 76 or 162? This way you would have a completely redundant system.

Anything raytheon is going to cost you $300 min (at least it seems that way), without even knowing what it is.

** sigh **
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Old 01-13-2003, 06:07 PM
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Default DSC hook-up question

Here's the info. in case anyone else needs it:

Raymarine PC/SeaTalk/NMEA interface box E85001

Brokenlegdave: $149.00
DBMarine: $129.44

Gerg, I do keep a back-up handheld GPS. But I keep it loose for the 'ditch bag.' You aren't kidding about the raymarine prices. They are pretty proud of their stuff!
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Old 01-14-2003, 04:04 AM
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Default DSC hook-up question

Before you buy the converter, check the seatalk sentences out to make sure that they will be converted to the NMEA sentences you need for the VHF. The VHF manual will have a list of required data to obtain position. Also check the NMEA version to make sure they are compatable.

Casey
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