Could there be an AIS Transceiver/VHF radio in your future

[jssailem]

I did a query

Large, very large and ultralarge ships all look like tankers, except for the deck gear. Deck heights range from 40-120+ feet. ULCC supertankers have a 70-foot difference in the height above water when they're full, as compared to when they're empty. Container ships run 60-80 feet above water.​

So lets say the antenna is 100 feet above the water level. Adding the 8 feet you have above the water. This gives you a potential 108 feet. The radio horizon would be 12-13 miles.

The smaller freighters might not see you till you were with in 5 miles.

 

[Ilanortho]

Thanks.

 

[JohnShannon]

https://en.wikipedia.org/wiki/Line-of-sight_propagation

The radio horizon is 1.23* sort(height (ft))
The height is for both antennas so if your antenna is on the mast 65 ft and their antenna is at 100 ft the range is 16 miles.

If you have an AIS MOB do dad you are at at zero ft and the receive antenna is on the stern rail at 8 ft then the range is about 3.5 miles.

Marine traffic AIS web site works out to the Farallon islands (about 25 miles) if you poke around you find that receive antenna is at 1500 ft on some mountain. So a theoretical distance of 47 miles. At some point signal attenuation will limit the distance.

Marine traffic also gets AIS signals from polar orbiting satellites. These satellites cover the entire planet as it rotates beneath them in 12 hours. You see the boats on the website in the open ocean but have to pay $$$ to get the detailed info. The big ships transmit I think 12W but you even see that the satellites will pick up the 2W transmission of a pleasure craft sometimes. So it looks like the AIS signal even at 2W will propagate pretty far (100mi ) or so but curvature of the earth wins out. I think it argues for a splitter and using the masthead antenna for your AIS transmission ( or reception) for that matter.

 

[Ken Cross]

There is no technical reason AIS, VHF, GPS and DSC couldn't be combined on a single VHF antenna. It just requires multiplexing (The equivalent of including the splitter inside the radio to go to a single antenna.) Our military already does something similar for different functions . Some Narco avionics equipment even did it in the 1970s to combine VOR, localizer, and glide slope in a single receiver. It really is not a technical stretch. I suspect because no one does it that no one will as long as they can make greater profits selling individual equipment.

Ken