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Old 15-03-2011, 17:58   #31
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Re: Radar Reflectors

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Originally Posted by jobi View Post
oh I never thot about having a radar onboard...now I understand the benifits....cheers
Given a forced choice between radar and a chartplotter, I would go with radar. Other vessels just do not show up well on the chartplotter.
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Old 15-03-2011, 18:43   #32
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Re: Radar Reflectors

Here are some interesting (and perhaps useful) links to previous discussions:
Radar Reflectors
and
Radar reflectors

You will find some good info on reflector performance, reflector height considerations, and the pros and cons of various solutions. The reflector technology really hasn't changed in the last few years.

My best advice: Don't get the Mobri and think you're covered. You're not.
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Old 15-03-2011, 18:53   #33
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Re: Radar Reflectors

The only thing you should depend on is YOU and your boat and crew.
I would rather have a good chart plotter with AIS on the screen.
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Old 15-03-2011, 18:56   #34
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Re: Radar Reflectors

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The only thing you should depend on is YOU and your boat and crew.
I would rather have a good chart plotter with AIS on the screen.
And where does the AIS data originate from that is being displayed on your chart plotter? your boat?
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Old 15-03-2011, 19:38   #35
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Re: Radar Reflectors

Well, it's just like all the other units, the VHF.
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Old 15-03-2011, 19:56   #36
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Re: Radar Reflectors

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The only thing you should depend on is YOU and your boat and crew.
I would rather have a good chart plotter with AIS on the screen.
While large commercial vessels use AIS transceivers, others use receivers only or are not equipped.
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Old 15-03-2011, 20:03   #37
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Re: Radar Reflectors

A flat metal plate is the worst possible retro-reflector. Most (all) the retro-reflectors will use some configuration of corner-cube constructions - that is three flat metal surfaces meeting at right angles to each other, like at the corner of a cube. Bigger the better is the rule...it's physics.

I'm going to get an active transponder 'reflector'. Mainly to save windage and banging around.
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Old 15-03-2011, 21:32   #38
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Re: Radar Reflectors

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Well, it's just like all the other units, the VHF.
While VHF radio frequencies are used to transmit the AIS data, the data itself derives from the other ship's GPS, their AIS transponder, and whatever information they elected to type into the AIS transponder - they are actively transmitting the data, your are passively receiving data and hoping the data is accurate (plus hoping the other guy's AIS system is working in the first place).

The point is that if you wish to control the dataset then you need to actively create/generate the dataset. A radar you operate lets you actively look for the other boat, including boats that do not broadcast AIS data, boats that forgot to turn on their AIS, have a broken AIS, or are transmitting incorrect information.

If you're merely listening to someone else's AIS datastream then you are passively collecting information about which the provenance is unknown - do you want to depend on data with an unknown source that you do not control? Your earlier post regarding the chart plotter suggested that you're keen to know where stuff is AND that you want to be in control of the data; passive data collection does not provide that feature.

The only affordable active mechanism for finding the other guy that I know of is a radar (and we have our eyes as well). There are FLIR infrared thermal & light amplification imaging systems as well; I'm figuring they are outside the price range of the typical recreational boater's pocket book - these tools are certainly more than I can afford.

So we're limited to radar and eyeballs, unless there's another system I am not aware of... and radar isn't that cheap, especially after factoring in the mount and electrical power consumption.

- rob/beetle
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Old 15-03-2011, 22:11   #39
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Re: Radar Reflectors

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Originally Posted by beetle View Post
While VHF radio frequencies are used to transmit the AIS data, the data itself derives from the other ship's GPS, their AIS transponder, and whatever information they elected to type into the AIS transponder - they are actively transmitting the data, your are passively receiving data and hoping the data is accurate (plus hoping the other guy's AIS system is working in the first place).

The point is that if you wish to control the dataset then you need to actively create/generate the dataset. A radar you operate lets you actively look for the other boat, including boats that do not broadcast AIS data, boats that forgot to turn on their AIS, have a broken AIS, or are transmitting incorrect information.

If you're merely listening to someone else's AIS datastream then you are passively collecting information about which the provenance is unknown - do you want to depend on data with an unknown source that you do not control? Your earlier post regarding the chart plotter suggested that you're keen to know where stuff is AND that you want to be in control of the data; passive data collection does not provide that feature.

The only affordable active mechanism for finding the other guy that I know of is a radar (and we have our eyes as well). There are FLIR infrared thermal & light amplification imaging systems as well; I'm figuring they are outside the price range of the typical recreational boater's pocket book - these tools are certainly more than I can afford.

So we're limited to radar and eyeballs, unless there's another system I am not aware of... and radar isn't that cheap, especially after factoring in the mount and electrical power consumption.

- rob/beetle
Rob is correct. Radar is an extension of our eyes particularly at night.

The other big advantage of radar is for plotting your position on chart if Plotter is down or in fog. As useful as AIS is not all vessels other than large ships are required to use it.
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Old 15-03-2011, 22:30   #40
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Re: Radar Reflectors

Can't always rely on AIS accuracy. For instance, the 226-foot USCG seagoing buoy tender Aspen continually travels at 102.3 knots moored according to AIS. Not to mention often information is missing such as draft, destination and estimated time of arrival for many, many other ships.
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Old 16-03-2011, 13:11   #41
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Re: Radar Reflectors

WoW!! too much technical info for this guy.. i like all the feedback and am taking it all to consideration, but honestly, i am leaning towards the one that grills steaks also, you know, duel purpose!!

I wonder how well a mounted beer keg would do?
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Old 16-03-2011, 13:26   #42
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Re: Radar Reflectors

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I wonder how well a mounted beer keg would do?
It would probably cause some party minded chaps to automatically set a collision course with your boat.
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Old 16-03-2011, 18:11   #43
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Re: Radar Reflectors

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I wonder how well a mounted beer keg would do?
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Originally Posted by Astrid View Post
It would probably cause some party minded chaps to automatically set a collision course with your boat.

Heh!

Bash.
I took my reflector off (well, it fell off mostly) but did not remove the grill.
No doubt you have tested this and it makes me feel good.

We love grilled steak.
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Old 17-03-2011, 09:18   #44
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Re: Radar Reflectors

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are cargo ships better equiped to see you on radar then the average fellow cruiser??
Yes they are.

They have radars with big antennas that provide higher resolution. They have radars operating on two frequencies. They have advanced ARPA and other electronics in their radars. They have officers properly trained in radar use. They have at least 1, often 2 people on the bridge at any given time.

Given all the above, I never get into their way inshore. Offshore, when a ship is spotted, as soon as I know what she is doing and if I find we might be getting much closer I simply tack away WELL before there is any risk of getting too close and then wait for the ship to disappear before I return to my customary 'doze' mode.

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