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Class B Transponder

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This year I used my new West Marine branded AIS Transponder. I was disappointed that on the two occasions I needed to contact a ship, one did not see me as an AIS target until we were 3 miles apart, and another only at 1 mile. I don't consider these short distances adequate or helpful.
Is there such a thing as a linear amplifier for the output?
I can receive other ship's signals from up to 50 miles away.
Can anyone else let me know what their experience has been?

2 Replies

  • Doug,

    1) No amplifiers are allowed, it would be wildly illegal to boost the output of your transponder.

    2) Use this distance calculator to see what the range should be based on the height of your antenna and the height of the antenna of the ship your receiving.

    For example, I put in that my antenna is at a height of 6 feet. I don't often see targets much further away than 10.5 miles, and get the impression I often first see targets at 4-6 miles.

    If I put into the calculator 6 feet high for both, I get 6 miles range. Well, thats about right.

    If I put into the calculator 6 feet high for me, and 30 feet high for another boat (about right for a small ferry or a tall power boat), I get 11 miles, which is about right too.

    3) How much is enough? I believe for coastal sailing where someone will be awake and sharp during the entire journey (e.g. not single handed crossing oceans, etc.), the range of a stern mounted antenna is just fine. Boats my own size I pick up in 4-6 miles, with a range that increases as the other boat is bigger and taller than mine, seems just about right.

  • The higher up the aerial, the further away you should see other boats and other boats see you.

    Are you using a splitter?

    Are you using a dedicated aerial?