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Raymarine forum - [DG11] ais 700 only 13 miles range, it's normal ?

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Full Version: [DG11] ais 700 only 13 miles range, it's normal ?
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Hallo,
sorry if I ask again about the " visibility range " of my new ais 700

Now I can see only ships at 10/13 nautical miles.

Before this ais, I had a Furuno ais only receiver and the range was 60/70 nautical miles. The boat is the same, the vhf radio too.

The diagnostic shows me that all works perfectly and the WSWR now is 1.2:1, so close to optimum value.

How is possible that the range is so short??

Thank you for the reply.

Ciao
Antonio
Hi Antonio,

Was the previous AIS a class A or Class B, bear in mind Class A has a higher power for transmission and a more sensitive receiver too.

AIS operates in a similar way to vhf and so is generally line of sight between the Antenna for the purposes of range. How high is your antenna mounted?

If your antenna is mounted at a height of 40ft above sea level, a range of 60 to 70 miles would suggest the other vessel's antenna is mounted at a height of 1846.5ft above sea level - this calculation found here is the accepted means of calculating range between two vhf antenna.

I would suggest that the range you previously observed is based on an AIS signal being repeated by shore based transmitters repeating transmissions.

regards

Derek
Thank you Derek,
So 13 miles i's a normal range for the Raymarine ais700?
Thank you.
My previus ais ( only a receiver ) was a class B, my antenna was and is located on my mast, the boat is an 42 feet.

What I kindly ask, is to know if only 13 miles is a normal range to " see " other ships on my plotter.Can you plese answer about this?

Grazie.

Antonio
Hi Antonio,
Thankyou for your feedback,

As I have previously stated, the range is entirely dependant on both the height of your own antenna and the height of the other vessel's antenna, we have reports from customers of ranges of targets received of up to 30 miles, and so given good atmospheric conditions, correct installation and cabling connections of both antenna this range is quite achievable.

Similarly a range of 13 miles can be quite normal if the transmitting vessel has a lower antenna or lower power from their antenna, or there is other interference in the area caused by external sources

Thank you

Derek
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