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Old 05-08-2014, 13:28   #91
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Re: DSC

Quote:
Originally Posted by ka4wja View Post
Skip,
This whole thread has drifted way off topic....and I'm just as much to blame as anyone...
So, without wanting to drift further, I'll give you some brief answers...
(yeah, you read correctly I wrote "brief"...


Specifics in red...




I hope this helps...


Fair winds..

John
s/v Annie Laurie
Of course. Your posts are always extremely helpful but in this case a little distressing (no pun intended). From what I have been reading about HF DSC I was afraid that a Mayday call would not be heard by commercial vessels which you have confirmed.

I guess this brings up the question, is there anyway to contact a commercial vessel with DSC SSB system with a non DSC HF radio?

So now I will have to factor that in to my overall emergency planning. There's still EPIRB, VHF DSC and connecting with a shore station on some HF band, marine or Ham. This all of course ignores the first line of defense which is to keep the boat afloat.
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Old 05-08-2014, 19:53   #92
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Re: Please School me on VHF/GPS/AIS Combo Units

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Originally Posted by ka4wja View Post
Lateral,
While the NZ Maritime Authority (Taupo Radio) doesn't monitor VHF-DSC (nor MF-DSC), just HF-DSC....and therefore NZ has no Sea Area A1 or A2, this does not mean that other vessels in your area haven't got VHF-DSC radios, and they could be potential sources of assistance / rescue, when you need it...Therefore, I would highly recommend that you:
a) Program your valid MMSI# into your DSC VHF radio...
b) Connect a GPS to the NMEA input...
And, learn how to send a DSC message...

I mean, worst case here, this would give you your GPS position on the radio display, for you to use/refer to, when making a Voice call....and still allow you to make a DSC call to other boats (whether a "Distress" message or just a routine call-up of a friend/buddy)


As for the AIS display on the 2150....it's pretty small....and with my eyesight, I'd never be able to use it effectively....so, the 2150 doesn't interest me...
But, you DO already own it, so why not at least give it a try???


I hope this helps..

Fair winds...

John
s/v Annie Laurie
Most definitely! Thanks John. Its just I have a lot of other things to sort out, including testing a M710 that I purchased of a CF member that currently have priority.
I have a VHF radio op lisc. from my PPL days, hopefully it is still valid, with a brushup, of course. And then I want to study for my Ham.

Immediate problem is I need a licensed contact down here to test my HF. I live in an enclosed valley so not much point rigging up a long wire here for testing. Anyway, need a licensed person. I will research for a contact.

I really appreciate the documentation/tutorial you have done on HF and I have copy & pasted into a file for "light" bedtime reading.
Of course, I should have considered an M802 but was economising.
Thanks again,
Roly
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Old 06-08-2014, 10:08   #93
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Re: Please School me on VHF/GPS/AIS Combo Units

Roly,
You're quite welcome...

And, here's some good news...
It's a myth that you need to have a "flat terrain" in order to make an HF radio work....
Quote:
Originally Posted by lateral View Post
Immediate problem is I need a licensed contact down here to test my HF. I live in an enclosed valley so not much point rigging up a long wire here for testing. Anyway, need a licensed person. I will research for a contact.
-- Almost all (< 98%) HF communications is via "Skywave"...

-- These "skywave" signals propagate at all sorts of angles at various frequencies and various times of day...(from as low as 4*-5*, to as high as straight up, 90*...)

-- Long range HF comms (5000 miles+), on frequencies of 12mhz-14mhz on up to 25mhz-28mhz, generally have very low angles of 4* - 10*....
BUT...
But, shorter ranges will have higher angles, of 10* - 20* - 30*...
(and unless you are in the bottom of a deep valley, completely surrounded by very steep mountains / cliffs, you're likely to have your signals radiate over the top of the hills well enough for some shorter range comms on 12mhz - 16mhz, out to a couple thousand miles...)

-- But, the REAL good news is that daytime HF communications on the lower frequencies (2mhz - 8mhz) is usually limited to short ranges covering just local/regional areas (from 20 - 600 miles, typically), and is always via Near Vertical Incidence Skywave (NVIS), with propagation angles of 60* to 90*!!!
So, unless you are at the bottom of a deep cave, you CAN use your radio very effectively for daytime HF comms on these lower freqs....
I suspect that 8mhz will work well for you at daytime ranges out to 500 miles, or so....(depending on antenna...)

-- And, it is the ANTENNA that you'd use on-shore to test things with, that WILL BE the most important part of the system....

-- Not sure if you have an AT-130 tuner to go with that M-710...
But, if you do, you have a easy way to test everything....

Antenna ideas...
In your location / your application, Do NOT try to use a vertical antenna....only try horizontal antennas....
{horiz antennas that are 1/2 wave high will have a 6db+ advantage over a vert. AND have enough low angle radiation for long range comms....horizontal antennas that are 1/4 wave high or lower will have VERY high / NVIS-like radiation and will be VERY effective for daytime comms on 2mhz - 8mhz, out to ~ 500 miles...
Vert ant, over ground, not sea water, have very low gains and have fairly low angles of radiation, and are very poor NVIS antennas...and are actually poor long range antennas for the higher freqs on-shore vs. on sea water....
I won't bore you with further details....just do not attempt/evaluate your M-710 with a vertical antenna on shore / in a valley, as you will think the radio is broken!!!}

a) Best:
Get some copper wire....150' - 250'....cheap scrap wire will work....
Throw it up as best you can in a square / triangle / loop, about 25' - 40' high (as best you can, it is not critical), use trees, poles, edge of roof, etc., place the AT-130 in the air / on the roof / under the eave / on a pole / etc. at least 10' - 15' high (or as high as your wire, if possible), attach one end of the wire to the AT-130's "antenna" terminal and the other end to the AT-130's "ground" terminal....
And, you're done!!
You now have an excellent NVIS antenna for 4mhz - 8mhz, and a decent skywave antenna for 12mhz - 28mhz....all for the cost of some wire...

b) Good:
Do similar as above, except...
Get some copper wire.... two lengths 50' - 60' long (100' - 120' total), attach one to the AT-130's "antenna" term, and one to the AT-130's "ground" term, throw the wires up in the trees, etc. as best you can, and still keep the AT-130 out and up as best you can...
And, you're done...
You now have an "auto-tune dipole"...

c) If you do not have the AT-130, then you should build/install a few coax-fed resonant dipoles (468/freq(in MHz) = total length in feet....feed with coax in center....
I suggest one for 8mhz to start with...

The list of antenna possibilities is endless....but the above are some effective and cheap recommendations...
Remember do NOT attempt to try a vertical antenna...as your results will be disappointing!!!




--- As for licensing...
Not sure what NZ maritime radio regs require....but you should have an HF radio license for your boat (w/ a callsign), yes???
If so, I don't see any reason not to use that callsign just to test the radio out, by calling Taupo Radio???
I suggest a phone call to them ahead-of-time, to arrange a test on 8294khz
(8,294mhz), instead of calling them on the Safety/Calling freq of 8291....

But, maybe one of your fellow Kiwi sailors will simply volunteer to help you, and test your radio out...


{and just an FYI....during my nighttime here in Florida, USA, I can regularly hear Australian Maritime weather on 8176khz (8.176mhz), and daytime/later afternoon, hear them 12362 and 12365....and that's 10,500 - 11,000 miles away from me....and I hear them quite regularly....so, if someone tells 'ya that HF doesn't work, walk away...}



I hope this helps...

John
s/v Annie Laurie
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Old 06-08-2014, 17:16   #94
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Re: Please School me on VHF/GPS/AIS Combo Units

Brilliant John!
Yup, AT30.
Now I will be able to set up at my home/office and get my head around receiving weather files, email etc etc. whilst studing for my Ham license.
We have some decent kauri trees sprinkled around the house, so all good.
Hope you don't mind the odd pm when I am flumoxed by something?
Save a thread hijack.


Thanks again for all your endeavours!!
I am at "base camp" here!

Apologies to the OP for the sidetrack.....

On topic.....I am thinking about outputting from the sh2150 to my plotter. IIRC,
this is possible,No? (With baud rate consideration of course.)
To alleviate "the old eyes", problem.
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Old 06-08-2014, 17:55   #95
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Re: Please School me on VHF/GPS/AIS Combo Units

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Originally Posted by wristwister View Post
Thanks again to all for your responses. I've learned a lot from this thread.

So I received my SH GX2200 (only $350 on Amazon!), installed it, played around with it, and did a little day sail with it, comparing it's AIS reporting with my visual verification. This thing is AWESOME! And I've barely tapped into it's capabilities. Every commercial vessal I saw out there had an AIS ping along with some (but certainly not all) of the smaller boats.

My only criticism is trying to make heads or tails out of the AIS traffic using that small display. I think this thing's really geared toward sending that data to a decent chartplotter, and showing it on the radio screen is just sort of a courtesy. But it does display traffic, and more importantly I can set up proximity alarms. I suppose this is one more reason I should consider forking over the bucks for a real marine chartplotter instead of just Navionics running on my tablet.

Thanks again all. Happy sailing!

Yes, glad to hear of it, particularly of the fun that can be had using AIS to see around low land, points and fog, etc. That little display is purely a token as far as AIS is concerned, but you can get the critical information you need, enough to know whether you need to consult the nav PC and/or plotter. I did notice something interesting the other day: the real-time AIS "polling" or delay in action when I saw a tug speed up from 4 to 8 knots or so and noticed that the AIS took about 20 seconds to change the SOG of the AIS target. Interesting to consider if a boat is particularly close (1/4 NM, say) and you are in fog as you might miss a course or speed change unfavourable to your vessel's interests. Still, a good tool. The next step is AIS-marked buoyage...never worry about drifting off-station again!
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Old 06-08-2014, 18:14   #96
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Re: DSC

Skip,
Of course, if you're within VHF range, then you have VHF-DSC....to call other vessels, whether Distress or Routine...
And, if you desired to contact a specific vessel individually, and if you knew the other vessel's INMARSAT phone # or their e-mail, etc., and you had a sat phone, and/or e-mail capability, then you could contact that specific vessel directly....


But, if beyond VHF range and you desired to contact all GMDSS equipped vessels, without a MF/HF-DSC-SSB transceiver or an INMRSAT-C terminal, there isn't a way to do what you desire....

Understand/Remember, it isn't just these commercial vessels that are monitoring MF/HF-DSC....but there are > 80 HF-DSC shore stations world wide, monitoring some or all of the HF-DSC freqs (on 4, 6, 8, 12, and 16), and > 450 MF-DSC shore stations that are monitoring the MF-DSC freq (2187.5khz)....



Skip, one important thing I do not want to get lost amongst this discussion of DSC....
Quote:
Originally Posted by skipmac View Post
So now I will have to factor that in to my overall emergency planning. There's still EPIRB, VHF DSC and connecting with a shore station on some HF band, marine or Ham. This all of course ignores the first line of defense which is to keep the boat afloat.
Regarding "emergency planning", a modern Class D VHF-DSC-FM radio, connected with decent/low-loss coax, to a masthead antenna, should ALWAYS be everyone's first, and highest, priority!!!
Next would be, a properly registered 406mhz GPS-equipped EPIRB....

And, only after that would be MF/HF-DSC-SSB radiotelephone...and/or an INMARSAT-C terminal....




Just wanted to share the above, so there would be no misunderstandings...

Fair winds...

John
s/v Annie Laurie
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Old 06-08-2014, 18:41   #97
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Re: Please School me on VHF/GPS/AIS Combo Units

Quote:
Originally Posted by S/V Alchemy View Post
...The next step is AIS-marked buoyage...never worry about drifting off-station again!
Aren't they doing it already? ATONS

Thanks to John and all the contributors to this thread, very useful and bookmarked.
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Old 06-08-2014, 21:44   #98
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Re: DSC

Quote:
Originally Posted by ka4wja View Post
Understand/Remember, it isn't just these commercial vessels that are monitoring MF/HF-DSC....but there are > 80 HF-DSC shore stations world wide, monitoring some or all of the HF-DSC freqs (on 4, 6, 8, 12, and 16), and > 450 MF-DSC shore stations that are monitoring the MF-DSC freq (2187.5khz)....
Hi John,

Could not have quoted the specifics but yes was aware that the DSC channels are monitored by numerous shore stations (courtesy one of your previous posts on the subject). I was thinking in the context of how to make direct contact with vessels in the area if I had to make "the call".

Since you confirmed my suspicion that a call on non DSC HF radio wouldn't be heard by another vessel then what about this scenario. It hits the fan and I set off the EPIRB and nearby vessels are alerted and come looking for me. Is there then some mechanism for communicating on HF freqs at that time?



Quote:
Originally Posted by ka4wja View Post
Skip, one important thing I do not want to get lost amongst this discussion of DSC....Regarding "emergency planning", a modern Class D VHF-DSC-FM radio, connected with decent/low-loss coax, to a masthead antenna, should ALWAYS be everyone's first, and highest, priority!!!
Next would be, a properly registered 406mhz GPS-equipped EPIRB....

And, only after that would be MF/HF-DSC-SSB radiotelephone...and/or an INMARSAT-C terminal....

Thanks. With one minor modification that is my priority list. The only change I would make is to add a waterproof, handheld VHF with DSC for backup and the ditch bag.
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Old 07-08-2014, 11:15   #99
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Re: Please School me on VHF/GPS/AIS Combo Units

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Aren't they doing it already? ATONS
Yes, but it's not widespread in many places.

I also agree that the related and allegedly off-topic commentary is of great use. I would point out that while a VHF voice call has a well-known range, a DSC call (with "report") can go farther due to the short burst nature. We were taught in my radio course that a DSC Mayday could be relayed a surprising distance, or could be picked up by a sufficiently elevated shore station far beyond what a Ch. 16 MAYDAY could be. Of course, if a lat/lon co-ordinates are included in the DSC MAYDAY along with "abandoning" as a report, the SAR folk or even nearby vessels have a huge advantage when it comes to pulling you out of the drink. So instead of thinking of DSC as a way to make VHF less of a "party line" or to automate calling similarly equipped boats, it can also be thought of a coastal form of an EPIRB, capable of sending a position AND a message, if selected. Doesn't lessen the desire to have an EPIRB, of course, but it's just another means to get attention when it's needed.
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Old 19-08-2014, 14:56   #100
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Re: Please School me on VHF/GPS/AIS Combo Units

One of the best collision avoidance measures, especially useful in ship traffic lanes, is FREE. It is the USCG Vessel Traffic Service. USCG Sector Seattle uses channels 5 (northern Puget Sound) and 14 (south of Juan De Fuca Strait). They can tell you what opposing vessel traffic you should be concerned about, and alert other vessels to your position and track. They can tell you where fog is and is not and the visibility. And they have BIG radar!!! They really appreciate it when recreational boaters stay in touch with them...it makes their jobs easier. Think of them as the air traffic controllers for the waterways.

Victoria, Vancouver and Comox CACG also provide vessel traffic services and are just as friendly.

BTW, you can get that SH GX2200 VHF/ AIS/ GPS/DSC combo for under $350. Watch eBay. But don't forget, the AIS function is receive only...it does not transmit your info. And if you are using the radio in Canada, you will need a special MMSI number. To get that, you will need to have a US Ship's Station License and Operator's License...couple of hundred $ covers both from the FCC.
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Old 20-08-2014, 10:35   #101
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Re: Please School me on VHF/GPS/AIS Combo Units

Quote:
Originally Posted by lateral View Post
On topic.....I am thinking about outputting from the sh2150 to my plotter. IIRC,
this is possible,No? (With baud rate consideration of course.)
To alleviate "the old eyes", problem.
It is possible, and easy to do. I tied our 2150 into a Garmin 740 chartplotter. The blog entry below should cover the basics. Standard Horizon tech support can also walk you through it over the phone in about three minutes.

http://elegantsea.blogspot.com/2012/...-standard.html
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Old 20-08-2014, 11:11   #102
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Re: Please School me on VHF/GPS/AIS Combo Units

It's always easier to spend other peoples money.

And calling an receive only AIS a "toy" isn't going to convert me to
send/receive. It only makes me walk away from that soapbox.

As I make my list of possibles regarding electronics,gear, etc.. I appreciate
what Mark said. I really like the idea of the VHF/AIS receive combo as a
starting point. As I develop my skill set I feel sure I will want to add the full
monty. Hopefully my kitty will be ready when I am.


Quote:
Originally Posted by Ex-Calif View Post
It's amazing how we have such an incredible
inability to put ourselves in the other guy's shoes.

What if his VHF had failed.

Op - "Dear CF. My VHF failed. Should I spend and extra $100 and get AIS
receiving. for $400?

OP - "Dear poster. You are a hazard to navigation. Please go buy $5,000
radar, $1,000 AIS transceiver and a $4,000 plotter before you even think
about taking your boat out again. You're welcome."

OP - "I'm on it! Do you think I should still get a VHF radio?"

This place cracks me up sometimes...
Great points Calif.
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Old 08-10-2014, 15:18   #103
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Re: Please School me on VHF/GPS/AIS Combo Units

Thanks again for all the advice and discxussion. I'm still loving my GX2200. Got another question, so I'll breath new life into this thread.

The GX2200 provides a selection of AIS ranges, from .5 nm to 25 nm. I pretty much pick up all AIS traffic out to the 5nm range, but nothing beyond that. No big deal, for the sailing I do 5 nm is more than enough range, but I'm wondering whether I should be picking up a longer range or not. I'm hooked to the mast top VHF antenna through good quality cable. I understand that land masses will block signals, but I've tried it in lanes with unobstructed 25+ NM views, still only receiving up to about 5 nm. Is this about as good as it gets? What are the factors that determine max range of AIS signal reception?
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Old 08-10-2014, 17:22   #104
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Re: Please School me on VHF/GPS/AIS Combo Units

First, are you sure there are AIS targets in your area between 5nm and 15nm? AIS is line of sight like VHF, so 15nm is a good benchmark, although if they are class A and out there, you will see some further.

Do you receive VHF transmissions from other boats at larger ranges? If so, your AIS should also.

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Old 08-10-2014, 17:40   #105
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Re: Please School me on VHF/GPS/AIS Combo Units

5 NM seems to be about the range. If I set the range (outer ring) to 10 nm, the inner ring is at 5 nm. I see boats magically appear close to that inner ring. They didn't materialize out of thin air, so I've got to assume I wasn't picking them up further out.

Regarding VHF reception, hard to say what my range is. I think this depends a lot on the power of the transmitter. For example, I can pick up coast guard transmissions from very far away, but I often can't pick up the boats that are responding to that transmission.
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