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NZ shipping lanes/radar reflector/ais


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Also, for anyone interested in a new vhf with ais receive only, I can do a special for crew.org members. A Lowrance link-8, for $475.00 incl gst. Send me a pm or email if you'd like one.

Bugger.. If I had known I would definately have bought off you. Do you have a website?

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If you (NZ and other visitors) travel the east coast of Australia for the first time ...be very aware that there can be ridiculous amounts of shipping especially near some of the bulk coal loading facilities..(these vessels at anchor can show up to 6 knots on AIS at the turn of the tide....but they are not under way).

Oh hell yes it's busy. Around Fraser Island is like a motorway at rush hour. It was around there we lost faith in AIS and have it tagged as OK but certainty not a bit of gear I'd put bugger all reliance in. Too many boats not showing until 2-3NM or less. Radar and eyes were better by many miles.  On another trip a ship that chased us heading into Sydney didn't show up until after it was that close we could hear it's engines it was that close, a spooky and another story in itself.

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KM, if you don't see multiple other vessels on your AIS until 2-3 miles, it is not working properly. Most likely a poor antenna. Class B should reliably give 5-10 miles, more sometimes, and Class A should be min 10 Miles - Ive seen vessels at over 50.  This is with a class B transceiver - it should still receive as well as a class A, its just it's power output is smaller, and, on out boats, the antenna is usually lower than a ship.

 

Sabre, yes I have a website - but that lowrance unit is not on it! Click on either the B&G advert or the Neptune's Gear one on the side of this forum. I do all the Navico stuff - so Lowrance, Simrad, B&G, and now also Raymarine electonics, puls Vesper, and a bunch of other stuff....

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Nothing at any stage told the crews of either boats the systems weren't working as they should.

 

Most of the crews on both boats thought 'La-de-do-da device with no contacts = no one there'.

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+1 for IT. We discussed this before after you got back from that Trip KM. The issue had to be in the receiving of the signal. Either the splitter or antennae or cable or the AIS receiver itself.

Yes, that can be an issue. The vesper ( and a few other units) have software with decent diags, and are likely to tel you if there is a problem. However, the power out meter can only tell you the unit is sending the signal at good power to the antenna, not that the antenna is actually using it effectively.

As Jon said, it's a tool, not the answer to all issues. Any/all electronics can have problems. As can mechanical devices, structures etc etc

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If you take a look at http://www.nmea.org/Assets/nmea%20collision%20avoidance%20through%20ais.pdf

They recommend a different spec antenna to the standard marine VHF antenna.

 

 

The AIS frequencies are on the high end of the VHF-FM band (@ 162mhz). Because of this, the standard marine VHF antennas are not manufactured for optimum performance at those frequencies.

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Reading the replies to this reminds me of sailing around the northern Capes in the 2011 RNI

We had a long chat via VHF with the coastal tanker Kakariki, they said we were a very poor radar target even though they could see us visually it was only when we were on the tops of the swells and their radar swept at the same time that we showed up on their screen. We were less than a mile apart.

It was after this and then doing a delivery up to the Islands on a yacht with AIS that I decided to fit one, also have it on current boat

To me for coastal and offshore it comes after a chart plotter and radar reflector in order of wants.

Apparently they work better with a seperate antenna but I've never had an issue with using a splitter and the masthead vhf one, defiantly works better the higher it is.

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The manual for mine has this spec:

The VHF antenna employed for AIS use:

Must be a dedicated antenna, i.e. not shared with any other VHF transmitter/receiver.

Must be suitable for marine shipboard applications (index of protection, ruggedness, means of mounting, etc.)  

Should be omni-directional and vertically polarised with unity gain (0 dB) with a bandwidth sufficient to maintain VSWR

Should be mounted with at least a two metre vertical separation distance from any other VHF antenna used for speech or DCS communication but see also the section “Radio Frequency Exposure Warning” below

Should be mounted at least 2-3 metres above sea level for full performance.

 

The SS Pacific Aerials one most of us have on the top our masts has this spec;

Specifications Frequency VHF 156-162 MHz Antenna Whip Stainless Steel Ferrule ABS Antenna Type Half Wave Gain 3dBi "Marine Gain" 6dB Typical VSWR at 156.8 MHz 1.2:1 DC Meter Reading Open Circuit Height 1.0m
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Specific AIS antennas do help get the best from any ais unit. I have them for $173+gst if anyone wants one. Best install is high up, a radar arch or spreader are common. However, using a high tech zero loss splitter( $381 +) and a standard antenna at the masthead also works well. Everything is a compromise on a yacht!

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Every time I use ours I love it. I only turn it on outside the harbour but am definitely getting a unit for the cruising boat as well.

Did another trip from Tauranga to Auckland on Sunday night left just after dark and the rain set in. There were about four ships anchored near Karewa and another three underway including one which came up from behind which triggered the alarm so I altered course to give a bit more margin it came across in front of us to anchor. Having the AIS just backed up what we could see and made it easier to identify which ships were underway and which were anchored. Gives a lot of clarity at a tense time while you try and work out where they are all headed.

Ours is a Garmin unit and has a splitter built in.

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hmm, pretty good unit though :-) but yeah a bit expensive. A bit more than the navico 400 series with a separate splitter, similar functionality. Similar price to a Vesper XB8000, with a splitter, but not as versatile as the vesper. No issue if its properly integrated into a system though. Id be happy with any of those....

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beats me why you'd want TX only.

The exact same reason you have a radar reflector, to make yourself more visible.

 

Ships are easy to see so the need for receive isn't the same.

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