Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 12-12-2015, 02:47   #1
Registered User

Join Date: Jul 2011
Posts: 270
Which AIS antenna splitter

I am thinking of splitting my VHF antenna to service a new black box AIS and see antenna splitters ranging in cost from tens to hundreds of dollars.

Is this really such a high tech item or is a cheap and nasty Chinese splitter all that is needed?

If it needs to be high tech then why split at all and just install yet another antenna
__________________

__________________
Hoghead is offline   Reply With Quote
Old 12-12-2015, 05:17   #2
Senior Cruiser
 
colemj's Avatar

Cruisers Forum Supporter

Join Date: Oct 2005
Location: Presently on US East Coast
Boat: Manta 40 "Reach"
Posts: 10,049
Images: 12
Re: Which AIS antenna splitter

The reason to use a splitter is when it is inconvenient, or even impossible, to install a second antenna in a location one desires. For example, at the masthead.

If you go with a splitter, you want a quality one that does not have any appreciable insertion losses. Also one that defaults on failure to the VHF. Very few have these specs, and those that do cost money.

The cheap ones will degrade your signal on both AIS and VHF significantly. You do not want a cheap one.

The only ones I know that meet criteria and specs I am comfortable with are the Vesper and the Navico spitters. There may be others that I am unaware of.

Mark
__________________

__________________
www.svreach.com

You do not need a parachute to skydive. You only need a parachute to skydive twice.
colemj is offline   Reply With Quote
Old 12-12-2015, 06:03   #3
Senior Cruiser

Cruisers Forum Supporter

Join Date: Jul 2006
Location: Chesapeake Region and Maine
Boat: 42' Bob Perry sloop
Posts: 4,038
Images: 4
Re: Which AIS antenna splitter

Don't do it. This question has been asked and answered many times.

Bottom line: Avoid the use of a splitter....any splitter. Why in the world would you take a chance on compromising the most important safety item aboard...the VHF???

Use another antenna. It doesn't have to be high; a small whip on the pushpit works well.

Bill
WA6CCA
__________________
btrayfors is offline   Reply With Quote
Old 12-12-2015, 06:36   #4
Registered User

Join Date: Jun 2012
Location: Port Aransas, Texas
Boat: 2002 Seawind 1000 (33 ft) Cat
Posts: 840
Re: Which AIS antenna splitter

Vesper splitter works very well with my masthead vhf antenna. Best performance for both vhf and ais. Not cheap but you get what you pay for.
__________________
sailjumanji is offline   Reply With Quote
Old 12-12-2015, 06:38   #5
Senior Cruiser
 
colemj's Avatar

Cruisers Forum Supporter

Join Date: Oct 2005
Location: Presently on US East Coast
Boat: Manta 40 "Reach"
Posts: 10,049
Images: 12
Re: Which AIS antenna splitter

What Bill means is that this question gets asked a lot and he is almost singular in answering it to the negative (among those with a lot of experience in this area). Why he twisted that statement to imply that the majority of experienced people think it is a bad idea is beyond me. Most agree that a good quality splitter does no harm, and can actually be better than a poorly placed or installed second antenna.

And several of the people Bill disagrees with have provided controlled experiments with actual measurements and data to support their contentions.

Bill has never done this - he just goes on record with this topic as "I am an expert, so do as I say".

Our splitter has a 15dB GAIN on the receive side and a <1dB loss on transmission. It is normally connected to the VHF, and fails over to the VHF with all reasonable failure modes. Without power, the splitter is a direct connection to the VHF. The antenna used is tuned to VHF 16, so there is no compromise with the VHF there. In no way does the splitter compromise the safety of the VHF.

It allows us to place our antenna so that the AIS transmission gain from the extra height far outperforms the tiny, tiny amount of insertion loss. <1dB insertion loss is immeasurable in practice on the VHF transmission.

If you, like us, consider the AIS safety functionality on par with the VHF in open waters (just try to contact anyone on VHF hundreds of miles from land, or even try to contact a ship anymore), then you will value the placement of the AIS antenna as high as possible.

But perhaps Bill's entire experience with splitters is with poor quality ones. Until recently, all splitters were very bad. If so, then he is correct to avoid those bad ones. If not, then I would like him to step up to the plate and provide actual experimental data that contradicts all of that from those who have provided it. Or even lay out his theoretical reasoning.

But please Bill, please stop just disagreeing on this and relying on your reputation for belief.

Mark
__________________
www.svreach.com

You do not need a parachute to skydive. You only need a parachute to skydive twice.
colemj is offline   Reply With Quote
Old 12-12-2015, 08:09   #6
Senior Cruiser

Cruisers Forum Supporter

Join Date: Jul 2006
Location: Chesapeake Region and Maine
Boat: 42' Bob Perry sloop
Posts: 4,038
Images: 4
Re: Which AIS antenna splitter

Well, Mark, thanks for the opportunity to present my views and reservations with respect to the use of VHF splitters. These fall into several categories.

1. Signal Loss. All splitters, even very good and very expensive ones like the Vesper, have some signal loss. According to factory specifications, the Vesper has 1% VHF transmission loss, meaning a 20.6% loss in transmitted power. On VHF receive (not AIS receive), there is a 1.5db loss, meaning a 29.2% signal loss. You can argue about whether these amounts are important or not.

2. Questionable Features. A 15db gain on AIS receive sounds great, and makes for good advertising. But, for most of us, WHO CARES? AIS targets show up just fine within a 3-10 mile radius even with no "signal gain" and a minimalist AIS antenna.

3. Practical and Engineering Considerations. Being a long-time radio enthusiast -- and a practicing one with daily long-distance contacts on the ham and marine bands -- as well as a marine installer/radio technician, I have seen just about everything imaginable on a boat. In any marine environment things tend to deteriorate. Surface corrosion, poorly installed connectors, coax deterioration over time, poor choice of coax, connections working loose, etc., etc. are the things which one sees every day.

IMHO, for most who do coastal and inland crusing -- that's most of us -- the VHF is the single most important electronic safety system aboard. Here you have a small unit aboard even the smallest boat which is capable of both voice and DSC emergency calls. I repeat my mantra: Why would anyone want to do anything to compromise this critical safety system?

A typical VHF fixed installation aboard a boat consists of the following:

Battery --> VHF Radio --> Coax --> Antenna

Simple, elegant, functional, robust.

Why in the world do ANYTHING to break up this simple chain, especially with an electronic device which has:

-- insertion losses (they all do);
-- a potential for failure (they all do);
-- involves additional connectors and connections (they all do); and
-- are not really necessary anyway as there are other alternatives???

4. Personal Experience. I have an AIS transponder on my own boat. It has a dedicated antenna on the pushpit. It is on 24/7. I have no trouble seeing or being seen. I see AIS targets as far as I want or need to, and others report that they see me just fine. The shore stations which pickup and report AIS signals see me just fine. The satellite-based AIS receivers see me just fine, according to USCG friends.

On a recent trip from the Chesapeake to Maine my AIS performed perfectly, transmitting and receiving as well as needed. And, my AIS system cannot possibly compromise my main VHF radio installation, and the VHF antenna atop my 64' mast. What's not to like?

And, Mark, just to set the record straight I'm NOT the only one who's been advising against the use of splitters. Others, mostly including VERY EXPERIENCED radio technicians/marine installers like Dave Skolnick, have repeatedly voiced their concerns re: the use of splitters in VHF circuits.

FWIW,

Bill
S/V Born Free
__________________
btrayfors is offline   Reply With Quote
Old 12-12-2015, 09:13   #7
Senior Cruiser
 
colemj's Avatar

Cruisers Forum Supporter

Join Date: Oct 2005
Location: Presently on US East Coast
Boat: Manta 40 "Reach"
Posts: 10,049
Images: 12
Re: Which AIS antenna splitter

Thanks for laying out your reasoning Bill.

Point #1: I will argue that a 20% loss is immeasurable in practice. And it is a worse case scenario. Others have shown data that the loss is less than this in practice.

Point #2: I care, as do others. That is a significant gain, and some of us appreciate being able to see boats at further distances and make decisions early. Particularly if conditions are nasty and one has limited choices in maneuverability (prevented wing-wing, for example).

Point #3: You have made no good argument on how a splitter compromises the VHF. In the good splitters, the failure mode is to the VHF. The added connectors is a red herring - particularly since they are in a dry area of the boat. The "other alternatives" are not always practical or even possible on some boats, and they also have compromises like distance and directionality. Also, I don't see why "majority rules" plays any part here. Who cares that the majority of users can live with different compromises than others? This doesn't make the minority compromises wrong.

Point #4: You are not projecting out much on this point. Your installation works OK for your needs - so what? It may be the exact wrong compromises for others. You seem blind to this whole fact.

The bottom line is that there are some compromises either way. Your choices are dead wrong for our situation, as well as for others. I have never said to ONLY use a splitter - and you are wrong to say that a splitter is ALWAYS a poor choice. Perhaps step back a bit and consider this.

I have read Dave Skolnick's opinion, and it mirrors yours - absolutely no experimental data to support it, just hypothetical beliefs maybe based on experiences with bad quality splitters. Being a scientist, I trust data. The data shown by other experts who have done controlled experiments show completely different results than you and Dave espouse. Including the addition of extra connectors!

Show me the experimental data supporting your viewpoint. Give me a good reason why a VHF would be compromised by use of a good splitter. Explain how all those connections decrease the signal. Explain how <1dB loss has any real-world practicality.

I assume your VHF is cabled with 1/2" Heliax? If not, you have compromised in transmission losses more than using a splitter.

See what I mean about compromises and choices (BTW, our VHF was cabled with Heliax)?

Mark
__________________
www.svreach.com

You do not need a parachute to skydive. You only need a parachute to skydive twice.
colemj is offline   Reply With Quote
Old 12-12-2015, 11:57   #8
Registered User

Join Date: Feb 2007
Location: Live in Boise, boat is in Titusville, FL
Boat: 56' CNSO Mikado Ketch S/V Solace
Posts: 231
Re: Which AIS antenna splitter

With new technology and lower costs this argument is becoming mute, at least when it includes purchasing a high end splitter for $200 plus.

Check out the Standard Horizon GX2200B combination GPS/AIS/VHF with DSC. I've seen them listed for as low as $300 including shipping.

They have gotten very positive reviews.

Amazon.com : Standard Horizon GX2200B Standard Matrix AIS/GPS VHF (Black) : Car Electronics

I didn't realize that this technology was available until I read this post and started researching VHF antenna splitters because I purchased an AIS receiver ($300) 18 months ago for my re-fit and have not installed it yet. Now it's already obsolete!

Good discussion with lots of strong opinions based on personal experience and sound data. This is the kind of stuff that makes this forum so helpful !

Thanks,

Jeff
__________________
Mikado is offline   Reply With Quote
Old 12-12-2015, 12:47   #9
Senior Cruiser

Cruisers Forum Supporter

Join Date: Jul 2006
Location: Chesapeake Region and Maine
Boat: 42' Bob Perry sloop
Posts: 4,038
Images: 4
Re: Which AIS antenna splitter

Jeff,

The GX2200B is an excellent VHF radio and the inclusion of AIS receive capability makes sense. It is very well done.

However, this is a receiver only: it does not transmit an AIS signal. While reception of AIS signals has some utility for mariners, I believe that AIS transmission capability is very important for safety reasons as well as for tracking.

Bill
__________________
btrayfors is offline   Reply With Quote
Old 12-12-2015, 15:20   #10
Registered User
 
ka4wja's Avatar

Join Date: May 2007
Location: Florida
Boat: Catalina 470
Posts: 2,033
Re: Which AIS antenna splitter

Hoghead, Mark, et al,
If you must use a splitter/relay, please use the Vesper SP-160...and try to make other improvements in your VHF radio system as well...(especially coax and connectors!)


---- Although this might surprise some, in general I agree with Bill here....for most cruisers, his advice/recommendations are good...

Vesper AIS SP-160 "relay/splitter" test results, lab/real world

Now, yes, I AM the guy that went and did the independent tests of the Vesper SP-160 splitter/relay...and found it to be an excellent unit, with excellent performance (including an approx. 4-6db of increased s/n on AIS receive performance)...
BUT...
Vesper AIS SP-160 "relay/splitter" test results, lab/real world


But...
a) the reason why someone would be compelled to use one, and...
b) how they can actually install/use one and NOT have any extra loss introduced into their system...

Neither of these are "typical" for most cruisers...

a) Sailing offshore in heavy seas, especially when heeled-over to windward, where a low mounted AIS transmit antenna has a high probability of being shrouded by the sea....along with the 30 second transmit interval of Class B AIS...making the likelihood of your sailboat's AIS signal reliably being received at any appreciable distance, pretty poor!!!
(most cruisers aren't ocean voyagers....and even the ones that are, are typically down-wind milk run sailors, and/or fair weather sailors....and even those times that they aren't in their "normal" environment, they might be motoring/motor-sailing, and less likely to be heeled-over in a heavy sea...and even then, more likely to keep a close watch on traffic, etc...)

b) If you figure that most cruising sailboats have rather poor VHF systems to begin with....sorry to say, but unfortunately that has been my experience!!!
So, if you look at the amount of loss in RG-58!! (6.5db/100')
Or even in some old RG-8x!! (4.6db/100')
And, then add in the loss of a splitter (1db to 1.5db, for the Vesper SP-160), well....
Well, you start to see where Bill's recommendations ring sound!!
BUT...

But, if you reduce your coax losses by the same amount of the splitter's loss, or even reduce your coax losses by MORE THAN the loss of the splitter/relay, well then you've actually improved things!!!
BUT...
But, here again that is NOT what most cruisers will do....
SO...


So, these two points are why I tend to agree with Bill....
(the fact that I have/use the Vesper SP-160 on-board my boat, notwithstanding.....I DO sail offshore in heavy weather, to windward....and I HAVE seriously reduced my coax losses!! And, the SP-160 is a fail-safe device...)




BTW, if anyone wishes to see why our VHF Marine radio system work so well....even when using lossy cable, old crappy connectors, etc...
Please have a look here, and learn something about path loss, line-of-sight, radiowave propagation, etc. etc. etc...

VHF and AIS Radiowave Propagation and VHF and AIS Radio Range



Fair winds...

John
__________________
John, KA4WJA
s/v Annie Laurie, WDB6927
MMSI# 366933110
ka4wja is offline   Reply With Quote
Old 12-12-2015, 16:04   #11
Senior Cruiser
 
colemj's Avatar

Cruisers Forum Supporter

Join Date: Oct 2005
Location: Presently on US East Coast
Boat: Manta 40 "Reach"
Posts: 10,049
Images: 12
Re: Which AIS antenna splitter

So John, you agree that use of a splitter compromises the safety of the VHF?

Would you agree that the quality of the installation of the VHF is independent of the use of a splitter? After all, a crappy job could also be done on the independent AIS antenna installation - rendering that useless as well. I don't understand your argument that a poorly installed VHF should be a reason to avoid use of a splitter.

In fact, a poor installation is even more reason to get the AIS antenna higher. I can't tell you how many rail-mounted AIS systems on cruisers we meet that don't show up beyond 2-3nm.

Again, I strongly disagree that just a few select offshore boats should be the only ones using a splitter. We have done more "on our ear" sailing inshore and coastal than offshore. I bet that is true for pretty much everyone who isn't out there doing expedition passagemaking. And inshore/coastal is where AIS is even more important than offshore.

I urge people to read your post that you link to - keeping in mind that you have been put between a rock and a hard place here regarding your personal friendship with Bill Trayfors. This is a very interesting conclusion from your experiments in light of your above post:

"I went ahead and added the SP-160, and found (no surprise) excellent results....much improved AIS range (as expected), and NO noticeable degradation in primary VHF radio performance, both transmit and receive worked as well as ever."

I'm sorry, but your above post and the URL linking to your experimental test results don't add up. Even your above reasoning doesn't make any sense - it all relies on a nebulous "bad VHF installation" to even suggest a splitter is a poor choice.

And then you and Bill ignore this "bad VHF installation" argument while advancing the argument that a splitter puts the VHF in peril!

So grow a pair here - you cannot have a thread on this forum showing experimental results proving that a good splitter has no effect on VHF performance, and that the additional connections required also have no effect on performance - while making good with Bill and qualifying the results of that thread to say they only apply to a very narrow slice of the population.

If you truly think that a splitter is bad for the vast majority of the people, please go back to your experimental thread and state this. Boldly and clearly. And explain your reasoning for your change of heart there.

If you won't do that, then explain yourself in this thread.

Sorry to put you and Bill on the spot here, but CF has been overrun by "experts" spouting unexamined beliefs and demanding that others take them based on their "expertise". I don't hold you and Bill in this category, but I do intend to hold your feet to the fire of proof and explanation, and won't let you just rest on "I have x years as a ham".

Please don't take this as discouragement from doing the experimentation that you do. It is of utmost value to the community, and rare in the marine industry. So rare, that I think you and a few others who do so know more about things than the engineers in the companies producing the products.

BTW, there are one or two other splitters besides the Vesper that work as well. There are not many of them, though. The one thing everyone should take from this thread is that "splitter" is not a generic term or item.

Mark
__________________
www.svreach.com

You do not need a parachute to skydive. You only need a parachute to skydive twice.
colemj is offline   Reply With Quote
Old 12-12-2015, 16:29   #12
Registered User
 
travellerw's Avatar

Join Date: Jan 2014
Location: Martinique
Boat: Fortuna Island Spirit 40
Posts: 1,721
Re: Which AIS antenna splitter

Another vote for the Vesper.. I have one on my boat and recently used it on a passage. I was able to see boats much farther than I needed (Class A ships at 40nm) and confirmed they could see me as far as 15nm. I kept in contact with a buddy boat and at one point we were separated by 30nm and still had clear VHF contact.

Argue specs and theoretical all you want, but my splitter works very well for me!
__________________
travellerw is online now   Reply With Quote
Old 12-12-2015, 17:29   #13
Registered User
 
transmitterdan's Avatar

Join Date: Oct 2011
Boat: Valiant 42
Posts: 4,019
Re: Which AIS antenna splitter

I do not subscribe to the theory that splitters are a bad idea for the majority of cruisers. Quite the opposite IMO. I am of the view that a good splitter (low loss on radio transmit and zero loss or even gain on receive) is the best solution for most cruisers with an existing VHF antenna on the mast head. There are some truly bad splitters out there. Don't use these! The Vesper splitter KA4WJA recommends is one of the "good" ones.

Everything is a compromise and the splitter with mast head antenna is the best compromise IMO. Another choice is to have 2 antennas on the mast. Either both at the mast head (not a good idea IMO) or the AIS antenna lower down on a spreader. This requires running a second VHF coax cable up the mast which is a pain for most cruisers. And the antenna at the spreader can cause problems with halyards, sails and sheets. Mounting the antenna upside down from the bottom of a spreader addresses some of these concerns.

Another choice is a rail mount for the AIS antenna. This configuration reduces AIS range considerably over a good splitter and mast head antenna. It has the advantage of providing a backup antenna when the mast head antenna is lost for whatever reason. But people carried spare VHF antennas long before AIS and it's still a good idea to carry a spare VHF antenna somewhere. The rail is as good as any place I guess.
__________________
transmitterdan is online now   Reply With Quote
Old 12-12-2015, 19:08   #14
Registered User
 
ka4wja's Avatar

Join Date: May 2007
Location: Florida
Boat: Catalina 470
Posts: 2,033
Re: Which AIS antenna splitter

Gee wiz guys, if I could edit/delete my post, I would!

This seems to be one of those subjects that many people here attempt to bend things around / read between the lines of....and/or take to the extremes....
(reminds me of the "SSB Ground" subjects!)

And, no I won't take the bait and get into an argument....
Please just read what I wrote...and the "why", below....and I think you'll understand...


So, here is what forms my OPINION...

Number 1...
Most "cruising sailboats" that I've seen / heard from have a rather poor VHF system on board....I'm sorry if that doesn't meet others' experiences / observations, but unfortunately, those are in fact my personal experiences / observations...

Number 2...
If you cannot get them to improve / update their systems in any decent way, you do a disservice to these very sailors that are seeking advice, by letting them walk away from their computer both uninformed and possibly making their system worse!
(heck, just this week here on CF, we've had member using a 15+ year old non-DSC VHF, and was bemoaning that he had to spend as much as $200 for a "new radio" when his old one developed a problem.....and other sailors who buy VHF antennas with RG-58 attached to them....and others who have ~ 25 year old installs, with who knows what condition their connectors are in, they finally buy a new radio, but still have a poor VHF system, etc. etc. etc.)....



Now, if you've got these sailors reading the discussions, anyone giving advice (especially those who are professionals, or who have worked in the communications / electronics field for decades), is doing a disservice to these very sailors that are seeking advice by just answering "yeah, I got 'dis spitter...she worx gud", or "yes, this one is good"...
In my opinion, we should be encouraging them to improve things, not make things worse....

And, this is why I "generally agree" with Bill!
AND....

And, if you actually read the other discussion that I linked to, you'll see the "numbers", and understand that while some sailors (I suspect you Mark, as well as myself and others), do understand that adding a db of loss will not adversely effect their own boat's system (or even better, they've reduced their system losses overall, and adding a splitter/relay will no longer adversely effect their system).....BUT...

But, just telling others to go ahead and "buy one", etc. doesn't represent what we call "good engineering" (or good seamanship), because we'd be forgetting that "others" aren't on our boats, and they are unlikely to understand the minutia of what makes a good VHF system....



So, with the caveats that I posted above (and earlier)....
Yes, I generally agree with Bill....
(And, no....I will not bite into an argument....

Now, while Bill's got a decade and a half on me....I do have ~ 45 years of RF / Communications experience of my own....as well as making a living in communications for > 30 years....and in addition to studying both radiowave propagation and antenna system design for more than 4 decades, I also teach these subjects....
And two things that I can tell you for sure are:
--- while the "math" might say one thing, you have to make sure that everything lines up perfectly, otherwise the "real-world" and what you "calculated", will never be the same!!
--- most cruising boats are not "perfect"!!


You can politely disagree with me....and I will not take offense....but, I stand by my words / opinions 100%...


Fair winds...

John
__________________
John, KA4WJA
s/v Annie Laurie, WDB6927
MMSI# 366933110
ka4wja is offline   Reply With Quote
Old 12-12-2015, 21:22   #15
Registered User

Join Date: Jul 2011
Posts: 270
Re: Which AIS antenna splitter

Ohhhhhhhhhhh I've opened a can of worms!

I think that given the need for a "good" splitter, another "good" cable and those inherent costs, I will just use a separate VHF arch mounted antenna. Not as good as the masthead, but better than mounted on the rail when heeled.

Installation is not much more difficult, and a backup second antenna if ever needed.

Now which antenna?

Which cable as it seems that all are not created equal?
__________________

__________________
Hoghead is offline   Reply With Quote
Reply

Tags
ais, antenna

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
AIS Antenna Splitter ChannelIslander Marine Electronics 21 13-04-2015 15:23
For Sale: AIS-MULTI AIS Receiver with built in Antenna Splitter kokomodenny Classifieds Archive 1 17-09-2013 09:53
AIS Antenna Location / Splitter FSmith Marine Electronics 41 27-08-2011 04:53
VHF Antenna Splitter for Phone lockie Marine Electronics 4 26-08-2010 17:19
Smart Radio Antenna Splitter (for SR161, SR162 AIS receivers) Randomandy Marine Electronics 11 19-12-2006 21:51



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 14:26.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.