Trundlebug
Well-Known Member
Let's not forget that the OP is asking about receive only AIS
Glad you knew that, it wasn't stated in the OP
AIS aerial vs AIS/VHF splitter
- Thread starter Champagne Murphy
- Start date
Glad you knew that, it wasn't stated in the OP
PaulRainbow
Well-Known Member
Champagne Murphy
Well-Known Member
As things are I've no real wish to 'send' AIS. Every time I go anywhere near an area of boat concentration the blue bits get masked out by the red AIS arrows. That includes sleeping boats in marinas.
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RichardS
N/A
Champagne Murphy
Well-Known Member
Richard
Fat finger syndrome!
PaulRainbow
Well-Known Member
Same here. Leisure sailors with AIS, who leave it on, are a pain in the arris. There are currently four in Shotley with AIS transmitting, at least one of them has been parked on a hammerhead for about two weeks. Doh !!
rogerthebodger
Well-Known Member
Going back to the AIS aerial vs splitter.
I have separate aerials but would like an aerial change over switch so I can select which aerial (mast head or pushpit) is for my main VHF radio and which is for my AIS receiver.
I do have a secondary fixed radio wit its own dedicated aerial at the no in case of a failure of any kind.
I have separate aerials but would like an aerial change over switch so I can select which aerial (mast head or pushpit) is for my main VHF radio and which is for my AIS receiver.
I do have a secondary fixed radio wit its own dedicated aerial at the no in case of a failure of any kind.
H35
Well-Known Member
I currently have a VHF with AIS receiver. But I will have a AIS B transceiver installed. I already have a splitter installed, for my FM radio. Not sure if I can add another splitter on top of it, for the transceiver??
I chose to mount a 2,5 meter Glomex on the rear of the boat instead of an antenna in the mast, simply because it was so much easier. So for it has survived 4 seasons without trouble. So for those without integrated AIS receiver in your VHFs, it's not that much trouble to have a (smaller) separate antenna for your AIS back there. And as mentioned, then you do have a ready back up antenna when you need it.
I chose to mount a 2,5 meter Glomex on the rear of the boat instead of an antenna in the mast, simply because it was so much easier. So for it has survived 4 seasons without trouble. So for those without integrated AIS receiver in your VHFs, it's not that much trouble to have a (smaller) separate antenna for your AIS back there. And as mentioned, then you do have a ready back up antenna when you need it.
johnalison
Well-Known Member
Sorry to add to your proctalgia, but I've just remembered that I forgot to switch our AIS off in Titchmarsh this afternoon. Fear not. I'm going down tomorrow and I'll do my best. If I remember. I do wonder what scale people view their stuff on if the odd yacht in harbour confuses them.
H35
Well-Known Member
Cracking up! Is this the British humour? Ha ha! (From a Norwegian....)
I don't know, but isn't there a setting on your AIS B transceiver that says "Anchored", or something similiar? And how the hedge does a boat at zero speed compute a line of course for collission calculations?? No, keep your AIS B on if you like, so I can find my friends and join them for a beer. Any commercial ship does, even in harbour. So what... :encouragement:
johnalison
Well-Known Member
No. A class B set doesn't have settings available to change. On the other hand, the fact that my craft is doing 0.00kn might give you a clue as to what I am about. It is the receiving boat that does the computation anyway. I don't recommend joining me at the moment for a beer, since the boat is locked and the fridge switched off. Some other time perhaps.
Lon nan Gruagach
Well-Known Member
[fred drift alert!]
CPA is calculated by reducing 2 moving objects at random places on a grid to 1 moving object randomly placed with the other being static at the coordinate origin. This is done by taking an initial point and subtracting the object vector (speed and heading) from that of the target object.
So... provided at least one of the 2 is moving the maths works. If neither are moving there is a special case that causes the maths to barf, this condition is caught in software and is translated to no possible collision.
[/fred drift alert]
CPA is calculated by reducing 2 moving objects at random places on a grid to 1 moving object randomly placed with the other being static at the coordinate origin. This is done by taking an initial point and subtracting the object vector (speed and heading) from that of the target object.
So... provided at least one of the 2 is moving the maths works. If neither are moving there is a special case that causes the maths to barf, this condition is caught in software and is translated to no possible collision.
[/fred drift alert]
lw395
Well-Known Member
The 'splitter' for the FM broacast receiver is (probably) a 'diplexer', a dual filter which separates the two signals according to frequency.
The 'splitters' we are discussing here are more complex devices which couple both AIS and VHF receive paths but switch one path off when the other is transmitting. (I'm not even sure that all VHF/AIS splitters are the same). The two signals are effectively in the same band so (practically) impossible to adequately separate by filtering.
lw395
Well-Known Member
I think that is a reasonable point of view.
Also a masthead antenna will be far superior when you are not on the open sea. If you are in port and want to know if there's an incoming vessel, or behind a headland it may make a useful difference. Depends where you sail and what you hope to get from your AIS I suppose.
Little Dorrit
Well-Known Member
Just installed an AIS transceiver with internal GPS and also purchased a VHF splitter (Digital Yacht AIS and Easy Split Splitter). Simple and easy installation. Seeing targets + 15M. VHF works fine, AIS recieves data and VHF all good too. Total cost less than £500... I will post here if it turns out to be a bad decision.
BrianH
Well-Known Member
Being troubled by my ranges above as they were quoted without any real historical notes, just a vague memory of past experiences, I was prompted to check today on my return to Italy.
It was not a day with exceptional conditions such as temperature inversions - or whatever causes long-distance propagation, just a bog-standard set of results, shown by the OpenCPN screen-shot as I neared my Italian destination.
From the AIS target list the cluster of moored vessels around Trieste are well in excess of 20nm as were others further south in the Adriatic (off-screen). The furthest ship was 37.3nm. As mentioned above, received on a half-wave Metz antenna (cut to AIS frequencies) mounted on the pushpit.
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johnalison
Well-Known Member
I generally reckon on about 40+ miles in general use! though I noticed an anchored ship at 57 miles today, with some land in between.
One of the handiest uses for AIS is to see if a ship is leaving a harbour that one is visiting or passing, even when hidden from view by a mole or buildings.
One of the handiest uses for AIS is to see if a ship is leaving a harbour that one is visiting or passing, even when hidden from view by a mole or buildings.
PaulRainbow
Well-Known Member
No rush, i was passing Titchmarsh this evening and disconnected your batteries, didn't want them going flat
Champagne Murphy
Well-Known Member
No rush, i was passing Titchmarsh this evening and disconnected your batteries, didn't want them going flat
Ric
Well-Known Member
I tried AIS with a Glomex stubby on the pushpit but range was not good - only about 10 miles or so sternwards and there was a blindspot forwards where range was only about 1 mile. I fitted a splitter and performance was greatly improved - about 50 miles - and I like that I can "see" on AIS any ships that will be in VHF range.
I kept the stubby as emergency aerial.