AIS receiver via VHF

[Phil23]

I am about to install an AIS receiver to be linked to my onboard dedicated laptop. I have a single VHF antenna through a 3 station manual select splitter, wheel house VHF and lower station VHF with one free station.
I have been told it is preferable to have a dedicated VHF antenna which I am not adverse to do if really necessary.
My question is my neighbour on the marina "winding me up" he tells me that AIS can be run through the VHF radio and no need for dedicated antenna.
Trouble getting my head around this is it correct and if so how do you set it up

 

[Iggy]

I would go with a separate antennas. Most splitters have some loss.

Here is the tricky thing about this, that I found out the hard way. VHF uses 156 to 157 MHz and AIS use 162MHz. SO you will need two antennas one tuned to VHF and the other tuned to AIS. Otherwise you have signal loss OR one broad band antenna that can do both. In other words, an antenna tuned to 159MHz that can handle both.

Using two antennas tuned for each use is the best way. No loss due to splitters or tuning.

 

[mvweebles]

I went with a splitter designed for AIS. Vesper and Navico each make one. They are close to $300, so roughly same price as a separate antenna.

Vesper has a decent analysis of the pros/cons of splitter vs dedicated antenna (HERE). For me, I already have two VHF antennae and would be difficult to add a third with proper separation.

Good luck!

Peter

 

[ranger58sb]

I am about to install an AIS receiver to be linked to my onboard dedicated laptop. I have a single VHF antenna through a 3 station manual select splitter, wheel house VHF and lower station VHF with one free station.
I have been told it is preferable to have a dedicated VHF antenna which I am not adverse to do if really necessary.
My question is my neighbour on the marina "winding me up" he tells me that AIS can be run through the VHF radio and no need for dedicated antenna.

For just an AIS receiver only, I'd suspect using a splitter would be OK. It's probably not like you'll care about some of the more distant signals you might be missing without an AIS-version antenna.

Why are you going receive only?

-Chris

 

[Iggy]

I went with a splitter designed for AIS. Vesper and Navico each make one. They are close to $300, so roughly same price as a separate antenna.

Vesper has a decent analysis of the pros/cons of splitter vs dedicated antenna (HERE). For me, I already have two VHF antennae and would be difficult to add a third with proper separation.

Good luck!

Peter

Form the above link "Using a splitter also means you can't transmit on your VHF and receive AIS updates at the same time." I forgot about this.

Not a big deal! But it adds to the pros and cons.

Another point that Ranger58 brings out, is range. Most likely your going with class B AIS which is only 2 watts. Range is about 5 to 7 miles. Now add splitter loss and/or tuning loss will bring the range down.

Just to point out, is you go with the new Class B (Class B SOTDMA) which is 5 watts. You will increase your range to 10 to 15 miles. Now add your signal loss if going with a splitter.

 

[Phil23]

I only need the AIS for coastal work I have purchased a New Zealand made unit manufactured by Marine electronics, best value for money

 

[Cigatoo]

I have Standard Horizon VHF and Em Trac B900 AIS with an internal splitter. Works fine. No loss of transmission power that I am aware of.
As an aside the AIS came from Milltech Marine. They have been very responsive and helpful with any questions that I have had. No affiliation just rewarding good service.

 

[Portage_Bay]

Like many here my system uses a splitter. Both the AIS and VHF work fine. Don't overthink this. As has been pointed out the cost of a splitter or a new separate antenna are about the same. Your decision should be based on which is easier to install. Buy quality gear and install it properly and you'll have no problems.


Ok, I said don't overthink this. Well here I go, guilty as charged.

Regarding range. I find the range to be more than good enough to give me plenty of time to contact the other boat and make arrangements and to give me a heads up that a 'big boy' is coming and give me time to get out of the way.

Regarding a splitter making it impossible for the VHF and the AIS to use the antenna at the same time. I find that is a non-issue. Any AIS receiver and or plotter I've used manages the load well. It takes longer to loose the AIS target(s) than the time the VHF is busy. True enough the targets will not update when the VHF is in use but the delay has never been long enough to even be noticeable. All of my long conversations are on the cell phone not the VHF. Unlike my working days I'm not using 3 or 4 VHF channels and transmitting frequently.

Regarding antenna placement. Yes there are recommended separations and it's best if you can observe them. But I've had to work on boats where it was not possible to meet that recommended separation and the VHFs work well enough. Occasional interference between the VHF sets but never enough to be a problem.

Regarding antenna tuning. Nonsense. A VHF antenna is designed to work on all of the VHF channels. The AIS channels are two of the VHF channels any VHF and antenna are designed to use.

 

[ranger58sb]

Regarding antenna tuning. Nonsense. A VHF antenna is designed to work on all of the VHF channels. The AIS channels are two of the VHF channels any VHF and antenna are designed to use.

Note VSWR spec are different:

https://shakespeare-marine.com/product/galaxy-vhf-antenna/?highlight=5225-xt

https://shakespeare-marine.com/product/galaxy-ais-antenna/?highlight=5225-xt-ais

VHF antenna centered on 156.8 MHz, AIS antenna centered on 162 MHz.

We have both, two XTs on two VHF radios, one XT-AIS on the AIS transceiver. I don't see any differences in reception or transmission, but then I also don't have a way to measure any differences.

-Chris

 

[Portage_Bay]

Note VSWR spec are different:

https://shakespeare-marine.com/product/galaxy-vhf-antenna/?highlight=5225-xt

https://shakespeare-marine.com/product/galaxy-ais-antenna/?highlight=5225-xt-ais

VHF antenna centered on 156.8 MHz, AIS antenna centered on 162 MHz.

We have both, Two XTs on two VHF radios, on XT-AIS on the AIS transceiver. I don't see any differences in reception or transmission, but then I also don't have a way to measure any differences.

-Chris

Yes you are correct there is a technical difference and you can purchase antennas designed for the two frequencies. I have a bit of experience running a high speed boat around other high speed boats where closing speeds head on were approaching 80 kts. The latest Class A units with separate antennas tuned for their respective frequencies would have been good. We didn't have them.

However I don't think it matters for recreational boaters especially at trawler speeds. I'll stay with my suggestion the OP make his decision based on ease of installation of either the splitter or the 2nd antenna.

 

[O C Diver]

On my boat, the Icom radio connects to the Garmin AIS transceiver and that connects to a 14' Shakespeare VHF antenna. While VHF is generally line of sight, targets within several miles will be picked up without line of sight. My system picks up recreational boats out to 20 miles and commercial ships to 50 miles. VHF radio transmission and reception are outstanding to the point where I have to turn the squelch way up to cancel very distant transmissions.

IMO, it doesn't matter whether you run it through the AIS transceiver or use a splitter. What makes the most difference is the size, quality, and gain of the antenna. When you're in trouble and need to be seen and heard by the Coastguard, the savings on a cheap radio and poor quality antenna won't seem so valuable.

Ted

 

[Iggy]

Note VSWR spec are different:

https://shakespeare-marine.com/product/galaxy-vhf-antenna/?highlight=5225-xt

https://shakespeare-marine.com/product/galaxy-ais-antenna/?highlight=5225-xt-ais

VHF antenna centered on 156.8 MHz, AIS antenna centered on 162 MHz.

We have both, two XTs on two VHF radios, one XT-AIS on the AIS transceiver. I don't see any differences in reception or transmission, but then I also don't have a way to measure any differences.

-Chris

I had friends tell that they could only see me on AIS within 1 to 1.5 miles. But I had no problems with the same unit on my last boat. I took it with me when I sold it, I but bought a new antenna for the new boat. I called Veper telling them about my problem. The tech had me pull up the web page. The VSWR icon was showing a antenna mis-match.

He said thats because I was using a VHF not a AIS antenna. Changed antennas, problem solved.

 

[sean9c]

When I was looking for my Vesper xb-8000 I talked to the guys at Milltech, I'd assumed that I was going to need a separate AIS antenna. He told me that the biggest issue that they see is signal interference between AIS and VHF antennas and recommended that I use the Vesper splitter instead.

 

[jclays]

I am about to install an AIS receiver to be linked to my onboard dedicated laptop. I have a single VHF antenna through a 3 station manual select splitter, wheel house VHF and lower station VHF with one free station.
I have been told it is preferable to have a dedicated VHF antenna which I am not adverse to do if really necessary.
My question is my neighbour on the marina "winding me up" he tells me that AIS can be run through the VHF radio and no need for dedicated antenna.
Trouble getting my head around this is it correct and if so how do you set it up

I have a Standard Horizons Matrix with AIS built in along with display. Only antenna is the VHS antenna. Wired to my Garmin Chart plotter I see the AIS targets on my Chart plotter's display.

 

[mvweebles]

When I was looking for my Vesper xb-8000 I talked to the guys at Milltech, I'd assumed that I was going to need a separate AIS antenna. He told me that the biggest issue that they see is signal interference between AIS and VHF antennas and recommended that I use the Vesper splitter instead.

Interesting - I Googled their guidance and was surprised

https://www.milltechmarine.com/VHF-...s 6 feet of,Most manufacturers recommend more.

In my personal experience, having two antennas even 4 feet apart can have a substantial impact on range. In one test I ran, I saw AIS targets 30 miles away with a single antenna. With two antennas 4 feet apart, the receive range dropped to 8 miles.​

Peter

 

[Iggy]

Below is from Milletech. This is the problem that I had. I was receiving just fine, but in transmitting I never knew that I had a problem until friends called me telling that I had to be close by. This is why I was saying, if your using a splitter with your existing setup be mindful of the specs of your antenna. To say this is nonsense, well................

"If you are using a VHF antenna – either an existing antenna or a new one – see if you can get the specs for the antenna to see how much tuning drop off you might expect at 162 MHz. For example, the Shakespeare Galaxy 5225-XT VHF antenna is tuned to 156.8 MHz with a nominal VSWR (more on VSWR later) of 1.5:1 but bandwidth falls off to 2:1 VSWR just 3 MHz away from the optimal tuning. Therefore 162.025 MHz (AIS2) at over 5 MHz away, would likely see a substantial deterioration in signal probably in the 3:1 or more VSWR range for AIS. The Shakespeare 396-1-AIS Classic AIS Antenna would be a better choice as either a dedicated AIS antenna or an antenna used with a splitter given the optimal tuning at 158 MHz – a bit closer to the 162 MHz AIS sweet spot – and its broader bandwidth (6 MHz within 2.0:1 VSWR)."

From Vesper
"However, your VHF antenna may not be well tuned at AIS frequencies which will lead to poor transmit performance. You can check your antenna performance at AIS frequencies by looking at the VSWR curves provided by the antenna manufacturer (they can sometimes be found on the manufacturers website). Look for a VSWR of 2:1 or less at 162MHz. Most VHF antennas are well tuned for 156MHz but will start to degrade at the extremes of the VHF band."

 

[Alisske]

Lots of sound advice. New splitters have minimal
Loss. VHf and AIS have different frequency sweet spots etc…..

I installed new AIS in my boat a year or so ago. The one thing that is most important is the cable. Signal Loss from the length of run is horrendous.

I had a 26 foot down east and and considered mounting on a pole (i was going way, way offshore on a 5 day solo trip and did not want to get run over during a nap break.)

Researched it and bought a 1/2 thick cable for a 12 foot run mounted antenna on the bonnet that was about 8 foot iff the water. I was picking up AIS signals 15 miles away in the harbor.

Bermuda Radio picked up my AIS 40 miles off and radioed me on the VHF.

Just put some thoughts into the cable. Was sort of a bitch to run it that thick, but worth it.

 

[heysteve]

We used a Raymarine AIS700 transceiver that has an integrated splitter for several years and had no issues. This includes very busy BC ferry traffic zones and Pacific offshore encounters with various size boats. No problems. Don't overanalyze it, you'll be fine with a quality splitter.

 

[Antares]

My experience is receive only a shared antenna is satisfactory.



I am using a single antenna with my Horizon VHF that also receives AIS. It is working fine for our current purposes. We spend very little time transmitting with the VHF so we have no issues with keeping current with AIS targets on our chart plotter which is connected to the radio via NMEA 0183.



I will most likely go to an AIS transceiver this spring. At that time I will install a dedicated AIS antenna.

 

[genedanko]

I do not use a splitter on my boat and strongly recommend the same to others. Here's why: AIS messages are 26.6 milliseconds long. Class A signals are generated at intervals of 2-30 seconds while most Class B signals are generated at 10-30 second intervals. The chance of a transmission getting stomped on by a voice message override is just too high.

The electrical discussions are all worthy. Just don't neglect the argument that a splitter must prioritize which signal to pass and which to reject. The duty cycle of an along (voice) distress is much higher than an AIS distress -- this puts AIS at a disadvantage in distress situations.

 

[Phil23]

several requests via email for info on AIS unit, go to:
aisdigital.com.nz


Please give me your opinions.

 

[Nepidae]

AIS reciever

First, I didn't see anywhere which AIS you were purchasing.

Are you going A or B?

What specifically are you using AIS for? Awareness of surroundings, foul weather needs due to topography?

I had A installed in '16 with a full Garmin suite and then in '20 updated to B.

AIS is an integral part of the safety of our boat due to the fact of cruising the inland rivers & canals where tows seem to congregate. It puts things into perspective to be contacted by a tug pushing 12 to 15 barges asking you where you want to be.

For situations like that the agreement is always made to the tug captains needs and has never failed.

I realized that I could save a few bucks to split the VHF with my Standard Horizon 2200 but is a couple of $$$ really worth it? I didn't think so. Any risk to transmission I felt was unnecessary.

We went with an independent VHF antenna and the system, overlaid on our 8616 MFD has worked flawlessly.

Stay safe out there.

 

[Mako]

I agree with @alisske’s comments regarding paying more attention to your cable. I mounted an 8ft Shakespeare right above my VHF on the overhead. Heeded the mfg’s advice for a minimum of 3ft of cable. Our range out at sea was phenomenal, especially since the tip was only 16ft off the water.