AIS Range

[colemj]

Originally Posted by FamilyVan

My GX2200 has a maximum display range of 10 miles (as pointed it out- it will detect further, just not show the vessels on the graphical display.

Is this so? Our GX2100 (the model preceding yours) has a max display range of 15nm. Wonder why they decreased it?

Mark

[FamilyVan]

Can't get it to range up any further. I was kind of surprised when I was playing with it, knowing I should expect a functional range of about 25 miles.

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[colemj]

The default setting is 10nm. To change it, go to menu>AIS/Compass setup>Display Range.

There you should see settings for 0.5, 1, 2, 5, 10, 15nm. At least that is how our GX2150 is.

You will also want to choose the highest Activation Range (50nm for ours), because I think that is also set at 10nm as default. It is in the same AIS/Compass setup menu.

Mark

[FamilyVan]

Originally Posted by colemj

The default setting is 10nm. To change it, go to menu>AIS/Compass setup>Display Range.

There you should see settings for 0.5, 1, 2, 5, 10, 15nm. At least that is how our GX2150 is.

You will also want to choose the highest Activation Range (50nm for ours), because I think that is also set at 10nm as default. It is in the same AIS/Compass setup menu.

Mark

Brilliant, thanks, I'll give this a try.

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[TxCoastSailor]

[QUOTE=MarkJ;1861456]100 feet? Thats a tiny ship. Panamx air draft is 190 feet so all the container ships will be up there somewhere.

My setup is good, and last trip i saw everyone at more than 40nms.
Here we see them at 50nms. And its not ducting!

Mark,

I can't dispute your display as it cleary indicates range to target at 50nm. Still, even in the ship's antenna is at 190ft his distance to horizon is about 17nm while your distance to horizon is about 10nm assuming your antenna is at the mast head. That adds up to about a 27nm range and you're seeing him at a distance about twice that. Not sure how that's happening. I'd be happy if I could get mine out to about 25nm. I do pick up VHF radio conversation out to about that range but no AIS targets. BTW what AIS transponder do you have? Mine is a Raymarine 650.

TCS

[Stu Jackson]

Originally Posted by FamilyVan

My GX2200 has a maximum display range of 10 miles (as pointed it out- it will detect further, just not show the vessels on the graphical display. This seems to be in keeping with the above guidelines.

Just a question from a potential user: How do you know the unit detects if you don't see it on the display?

[FamilyVan]

Originally Posted by Stu Jackson

Just a question from a potential user: How do you know the unit detects if you don't see it on the display?

There is a list feature in addition to the graphic display. List shows all targets detected, the graphic display looks kind of like a little RADAR screen.

Also, an independent plotter should show the targets (although I don't have one).

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[Fog Bank]

Originally Posted by FamilyVan

There is a list feature in addition to the graphic display. List shows all targets detected, the graphic display looks kind of like a little RADAR screen.

Also, an independent plotter should show the targets (although I don't have one).

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I wired our 2150's AIS output in the chartplotter and can confirm targets are shown well outside of the display range gate for the 2150's display.

[MarkJ]

Originally Posted by TxCoastSailor

I do pick up VHF radio conversation out to about that range but no AIS targets. BTW what AIS transponder do you have? Mine is a Raymarine 650.

TCS

Mine is also Raymarine 650. On ProAIS2 it has a VSWR of 1:1.1 What is yours?
its on a dedicated vhf antenna at mast head.

You should get aIS much further than voice as its digital packaging.

I run mine via the USB cable direct into the laptop running OpnCn. I know the ranges are not false nor ducting as I have had it for 3 years now.

I hope this helps because its truly great when it works well.

[continuouswave]

Originally Posted by MarkJ

...You should get [AIS] much [farther] than voice....

The range of any communication circuit is based on the signal level at the receiver and the receiver sensitivity. Receiver sensitivity is based on the design of the receiver, and typically is specified by the manufacturer. Sensitivity is specified by two terms: a signal level, and the degree to which the original modulation of the signal is recovered at that signal level.

To compare the range of a VHF Marine Band transmission by voice to an AIS data transmission, we look at the the path loss equation and the receiver sensitivities

The path loss will be the same for both systems. If the transmit and receive antennas and their feedlines have the same gains and losses, these variables will be the same for both VOICE and AIS transmission. We assume all elements of the signal level equation will be the same, except transmitter power. Typically the VOICE transmission will be at 20-Watts while an AIS Class B will be at 2-Watts. This gives a 10-dB advantage to VOICE compared to AIS.

We next look at receiver sensitivity. For an AIS receiver, the sensitivity is typically specified as better than -107dBm for 20-percent packet error rate (PER).

See: http://digitalyacht.co.uk/files/AIS%...ON%20TABLE.pdf

A typical FM VHF voice receiver is rated for a sensitivity of 0.25-microVolt for 12dB-SINAD. Converting this voltage to dBm for a 50-Ohm antenna system results in -119dBm

See: continuousWave: Whaler: Reference: Marine VHF Radio Communications.

We see that the sensitivity of a VHF Marine Band voice receiver is 12-dB better than the AIS receiver.

Since VOICE has a 10-dB advantage in transmitter power and a 12-dB advantage in receiver sensitivity, it is difficult to conclude that AIS transmission will have a greater range than VOICE transmission.

For a more extensive discussion of this topic, see

http://continuouswave.com/ubb/Forum6/HTML/003657.html

[colemj]

Originally Posted by continuouswave

Since VOICE has a 10-dB advantage in transmitter power and a 12-dB advantage in receiver sensitivity, it is difficult to conclude that AIS transmission will have a greater range than VOICE transmission.

I agree with all of that except for one thing - AIS is a digital signal, so will be able to pull intelligent data out beyond analog voice (which will be variable depending on how well one hears and understands the transmission, as well as the fidelity of the output).

Earlier, I stated that AIS would have a very slight increase in range over VHF for this reason. However, it is just a gut feeling.

Mark

[jstevens]

+1 what ContinuousWave said, even though I don't really know that much about radio waves. I passed my General Ham License tests 10 years ago, and have forgotten 90% of what I learned.

I do have personal experience with the digital processing of data signals - I own a HD TV.

When a digital processor receives a signal, the data is validated by various integrity checks. If the checks are not 100% validated, the signal is thrown on the floor. Your AIS receiver may receive a transmission from 100nm, but most times it will not pass the checks and is discarded. The VHF voice receiver makes very few quality checks (e.g. signal below squelch level) before it sends the transmission to the speaker. The human ear and brain can often make sense from even a very garbled transmission.

So it makes sense that, all other things being equal, the effective range of a VHF voice receiver would be greater than that of an AIS receiver.

John

[MYTraveler]

Originally Posted by continuouswave

Since VOICE has a 10-dB advantage in transmitter power and a 12-dB <dis>advantage in receiver sensitivity, it is difficult to conclude that AIS transmission will have a greater range than VOICE transmission.

Comparing Range for VOICE and AIS Transmissions - Moderated Discussion Areas

The extreme ranges experienced by myself and others are Class A signals. In that context, and since voice is 25 watts and Class A is 12.5, isn't that only about a 3db advantage, giving AIS a net 9 DB advantage? If so, that would give AIS a significant advantage, especially given the digital nature of the signal, as noted above by colemj?

[FamilyVan]

Originally Posted by colemj

Is this so? Our GX2100 (the model preceding yours) has a max display range of 15nm. Wonder why they decreased it?

Mark

It seems the 2200 maxes out at 10 miles. Also the acquisition range is limited to 30 miles.

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[TxCoastSailor]

[QUOTE=MarkJ;1861792]Mine is also Raymarine 650. On ProAIS2 it has a VSWR of 1:1.1 What is yours?
its on a dedicated vhf antenna at mast head.

Mark,

I didn't notice a VSWR reading in ProAIS. I may have an older version and I need to update it. I did check VSWR with a Shakespear meter and while I don't remember the exact value the needle was in the green zone.

TCS