Aerials for AIS

[PaulRainbow]

Not only that, but a good many are on motor or powerboats with much less height. Mine is at the masthead via a splitter and works perfectly well, but it seems that even a suboptimal set-up can be 'good enough' for practical purposes, even if it makes sense to achieve the best practicable.

Mine is on a mobo with 5m air draft.

 

[MontyMariner]

As I calculate it there is only about 1.46 cm difference between the two optimal lengths for CH16 and AIS.
(234/f Mhz = 1/4 wavelength length in feet)

 

[Refueler]

I conducted tests on my smaller boat ... with an ONWA passive splitter ... using my ONWA KP39A plotter / AIS unit ... VHF antenna at masthead and another at pushpit rail height. Note I was at my home mooring with a 3 - 4m earthen bank

Masthead was approx 10m above waterline ... rail about 2m above w/l.

I even tested without the splitter with antenna's connected direct.

Its some time ago - but numbers fell in region of :

WITH SPLITTER :

Rail : 5 - 6 targets to a range over 2mls
Masthead : over 15 targets to range over 10mls

WITHOUT SPLITTER :

Rail : 5 - 6 targets to a range over 2mls - no change
Masthead : 20 targets to range over 10mls

What I was pleased to see - all the AIS from yachts in the harbour showed up in all tests ... which I did not expect with the concrete walls etc.

I will be conducting the tests again later when season starts - this time from harbour ... on the later boat ...

 

[geem]

I conducted tests on my smaller boat ... with an ONWA passive splitter ... using my ONWA KP39A plotter / AIS unit ... VHF antenna at masthead and another at pushpit rail height. Note I was at my home mooring with a 3 - 4m earthen bank

Masthead was approx 10m above waterline ... rail about 2m above w/l.

I even tested without the splitter with antenna's connected direct.

Its some time ago - but numbers fell in region of :

WITH SPLITTER :

Rail : 5 - 6 targets to a range over 2mls
Masthead : over 15 targets to range over 10mls

WITHOUT SPLITTER :

Rail : 5 - 6 targets to a range over 2mls - no change
Masthead : 20 targets to range over 10mls

What I was pleased to see - all the AIS from yachts in the harbour showed up in all tests ... which I did not expect with the concrete walls etc.

I will be conducting the tests again later when season starts - this time from harbour ... on the later boat ...

We did away with the splitter set up on ours a few years ago. I wasn't convinced they work too well. We seemed to get better range with a dedicated AIS antenna, even though it was on the mizzen mast and not on the main mast(when we had the splitter). You findings confirm this

 

[Refueler]

We did away with the splitter set up on ours a few years ago. I wasn't convinced they work too well. We seemed to get better range with a dedicated AIS antenna, even though it was on the mizzen mast and not on the main mast(when we had the splitter). You findings confirm this

Of course - but note that was a non powered passive splitter.

If I was to install an active powered splitter - I would expect an improvement on that.

My point though was to illustrate even with the earthen bank - concrete walls - reception was still coming in on the rail ... of course as the masthead was well above all - that would be expected to greatly improve reception ...

I didn't mention - but my AIS even though its the early ONWA B+ at 2W instead of the later 5W AND via the passive Splitter .... my AIS was picked up by others in the harbour etc. AND by Marine Traffic. My mooring is across town and up river ! (ONWA was Class B - but soon swapped to B+ ... first versions were still at 2W but soon were 5W .... I knew that when I bought and was offered a discount for taking the old stock..... it works - that's all I need !)