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Old 24-06-2018, 10:15   #1
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OpenCPN AIS Range

Hi,

I am new to OpenCPN and wondering if I did everything right. I have setup the OpenCPN with a USB AIS Dongle. I went through all the calibration procedure. The problem I have is that I find that for AIS target that is further than 2nm I seem to lose them.

I am wondering if this is due to my dongle's limitation or if there is a setting in the system.

Thank you in advance.
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Old 24-06-2018, 10:34   #2
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Re: OpenCPN AIS Range

Receive range would be almost entirely dependant on your antenna. The higher / more efficient the antenna the longer the range. Second would be the efficiency of the receiver (dongle). The display (OpenCpn) is going to display whatever the receiver gives it and doesn't effect the range at all.
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Old 24-06-2018, 10:37   #3
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Re: OpenCPN AIS Range

As long as the position of the AIS target is within the area of the chart displayed, OpenCPN will plot the target. Any targets outside of the displayed chart area will still be included in the AIS target list.
Any range limitation is usually a limitation of the receiver. Where have you put you antenna that attaches to the USB AIS receiver?

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Old 24-06-2018, 11:48   #4
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Re: OpenCPN AIS Range

AIS signals are transmitted via VHF channels. So they have the same range as your VHF to talk to other ships or coastal stations. Usually up to the horizon.
However there exists a tropospheric ducting for VHF allowing signal transportations using reflections at the troposphere for more then 100 miles similiar the reflections used by the short wave community. This page shows a forecast of tropospheric ducting:
Tropospheric Ducting Forecast for VHF & UHF Radio & TV


I'm in the Mediterranean und using an AIS relais station about 100 miles away I receive AIS signals for more than 500 miles.


Gerhard
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Old 24-06-2018, 12:14   #5
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Re: OpenCPN AIS Range

Thanks guys.

I have in the antenna originally for my VHF radio. I use the Glomex to split to AIS. I am wondering if the Glomex is having a negative effect instead.
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Old 24-06-2018, 14:13   #6
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Re: OpenCPN AIS Range

Try connecting the antenna directly to the dongle. That will tell you if the splitter is the problem.

Jim
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Old 24-06-2018, 15:43   #7
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Re: OpenCPN AIS Range

Also, what Class of targets are you seeing that disappear at 2nm. Class B CS transponders are very low power and you only see them every 60 seconds with a single channel receiver. Do you see any Class A targets, and do they drop out at 2 nm?

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Old 24-06-2018, 22:05   #8
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Re: OpenCPN AIS Range

What dongle are you using? Most USB radios arenít very good but should receive more than 2 miles.
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