Then downside with a lower antenna (that’s what I have) is that range is less. Perhaps only 5 miles or so. Not a huge issue on a sail boat where we don’t move all that fast but it Is less. My AIS can see down the lake about 6 miles but friends with mast head antenna can see down the lake, over the dunes, and miles beyond.
I have my AIS antenna mounted on my stern railing and I'm able to see and be seen at around 25 NM. Certainly far beyond 5 nm! I've used it extensively - as in when I'm sailing it is turned on - I just finished crossing the North Atlantic Sailing in all kinds of weather and waves. Traveling up the North East Coast to Nova Scotia and Newfoundland, I had to sail in dense fog and was traveling 24/7. There were many commercial freighters and fishing boats that I could watch both where they were, where they were going and what my heading required. When I neared the European coast, I had extensive commercial traffic to contend with. My AIS was a godsend for navigating in those conditions. I could see the heading and speed of the freighters and my AIS would calculate the closest point of contact. Numerous times that was 0 NM - or stated in more blunt terms - predicting a collision course! Most freighters adjusted their rumb line, some did not and it was clear they weren't going to. So I followed the law of the jungle - bigger wins, I changed course!
No idea where you got the 5 nm, perhaps it's the unit you are running, but my AIS with antenna mounted on the stern rail works well, even in large waves (where I could see boats appear and disappear at the 25 nm range) at pretty much 25 nm, sometimes further.
dj
p.s. why would you care to see beyond the lake you are sailing in? What does that do for you? Just a question...
p.p.s. - OK ignore this post - I just discovered that my AIS antenna is indeed on my mast head! So I'm sending and receiving for my AIS at roughly 65 feet above sea level... see later post in this thread....