VHF - AIS antenna splitter ??

Daverw said:
Have you tried your current mast head vhf just with your AIS? this would confirm your thoughts regarding the possible range and additional targets you can see and give you something to compare with. I had a club member who was convinced his range was poor, when looked into this in more detail he was comparing what he saw from the boat to what he saw on marine traffic, he did not get that this is not a possible comparison
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Problem I have is that I am literally confined to short walks and rest of time reclined in bed. Its very difficult for me to enter cabin.

Connecting AIS to masthead antenna direct may be possible ... not sure how much antenna cable as its buried in toerail then to VHF mounted under side deck. But its good suggstion.

I am well aware of ranges expected by height / connections etc.

Comparing Marine Traffic !! Crazy ... I use MT in my work to check on my nominated ships in China / Turkey etc ... if I could use my own AIS unit that would save me a bunch of fees !! Joking of course.
 
neil1967 said:
I have a splitter on my Class B AIS and VHF (its a Digital Yacht one - if you take a look online you can see a world of difference between it and the passive device in question). I get around 20nm range on AIS targets in open water - antenna base is 17m above sea level - but I would expect much less range in an area as cluttered as your mooring. I can't see how any passive unit would work switching between AIS and radio - a passive unit is just a splitter that shares signals between devices rather than one that actively switches between them.
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I don't know how they can get a passive working as well ... but its a Branded unit sold for use with their branded plotters / VHF's which have nothing different to any other plotter / VHF ... so interested to see it work.

Checking online - I see that the main difference Passive to Active is Power Gain to boost reception / transmission signals ... nowhere can I find reference to powered switching.

Lets see when it gets here and I can fit it. My agreement with dealer is to write review and report back on it as its only been available since last year and very few reports. Brand to be named later - before anyone asks.
 
It is potential possible to design with very narrow band pass filters and other passive circuits but losses would be huge at the low transmission powers. When used on repeaters these are big units often rack mounted and very problematic and leaky.
Also useful to have on board coax extension lead anyway, socket / plug and coax
 
Interesting that 'beloved' Garmin say :

AIS and VHF Radio Using the Same Antenna | Garmin Customer Support

"AIS and VHF Radio Using the Same Antenna
The Garmin AIS 300, AIS 600 and AIS 800 are built with a built-in passive VHF splitter, which allows a single VHF antenna to be used for both the AIS system and a VHF radio. Since this is a passive splitter, the VHF radio will continue to operate properly, whether or not the AIS is powered.
Further instructions about installation of the AIS or VHF equipment can be found in the Owner's Manual or Installation Instructions for the device."

Seems quite a few Plotter / AIS units have passive splitters installed internally ...
 
Refueler said:
Interesting that 'beloved' Garmin say :

AIS and VHF Radio Using the Same Antenna | Garmin Customer Support

"AIS and VHF Radio Using the Same Antenna
The Garmin AIS 300, AIS 600 and AIS 800 are built with a built-in passive VHF splitter, which allows a single VHF antenna to be used for both the AIS system and a VHF radio. Since this is a passive splitter, the VHF radio will continue to operate properly, whether or not the AIS is powered.
Further instructions about installation of the AIS or VHF equipment can be found in the Owner's Manual or Installation Instructions for the device."

Seems quite a few Plotter / AIS units have passive splitters installed internally ...
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Em-track AIS transponders have built in splitters, too.
 
OK ... finally took a risk and got on board boat ... will probably pay price later today !

I disconnected masthead antenna from VHF and connected to plotter ... switched on ... within seconds I had 10 targets .. and the number kept increasing till 21 including ship at anchor outside port ...

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When I reconnected rail antenna ... that dropped to 1 target ....

rQe0IhC.jpg


The extra range was no suprise - but a large number of the 21 were at a range I would usually get some .. that is the Fishing Boat dock just past the bridge ... but rail antenna didn't.

Certainly makes one think .............
 
Hi Nigel. The question now is, Is the rail antenna OK? I understand most people find rail antenna ok for AIS so may be your is bad. Check continuity of cable and grounding. Then check VHF com performance with rail antenna. ol'will
 
William_H said:
Hi Nigel. The question now is, Is the rail antenna OK? I understand most people find rail antenna ok for AIS so may be your is bad. Check continuity of cable and grounding. Then check VHF com performance with rail antenna. ol'will
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The rail antenna is good ... its actually one I bought to replace the masthead one .. but when mast was down - I found the fault ... and never swapped them. It was shelved until I decided to use my AIS dongle on the boat. (If you have a Metz - as I have at masthead .... check the tightness of the lock holding the stainless whip ... mine had loosened over time).

Fi5bxZbl.jpg


I have an AIS that plugs into USB on computer ... I had it for use on ships when supervising Ship to Ship transfers ... I had a rubber duckie antenna for it ...

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Often I would call up the ship programmed to load from us and they would tell me ETA / on way etc. - but I was tracking them and had better idea !!

Having basically stopped doing Ship to Ship myself - I have Supers employed for it .... the USB AIS was in the drawer.

Obviously now - its redundant .... but still works. In fact maybe I'll connect it up to one of my computers and check my boats AIS transmission .... just out of interest.
 
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Rappey said:
I get that distance from my onwa with no antenna plugged into the plotter. Sounds like your antenna/coax is dead.
Antenna at 2m high gives me around 10-12 miles.
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My boat at that time sits in a channel with high banks and houses / structures between it and other AIS sources. Its actually surprising that I get those targets ..

har5FWOl.jpg


The bank is about 2m high next boat .. about 3m elsewhere ... then there's houses / structures between my channel and harbour ...

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I am probably only boat with AIS this side of the bridges - other than the low height excursion boat that turns near my channel
 
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