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Old 16-12-2015, 07:49   #46
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Re: Which AIS antenna splitter

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Originally Posted by Hoghead View Post
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
I have no clue about the theoretical details but:
When adding the AIS transponder I installed a splitter because I was too lazy to route cables and go up the mast. It was an "easyAIS OCB", not cheap @180 Euro.

Guess what: After a few weeks I bought a short AIS rubber antenna and mounted it on the spreaders.

Much better reception.

In my particular case the reception quality was barely OK with the chartplotter only. But it dropped massively when the OpenCPN PC was switched on, too.
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Old 16-12-2015, 09:17   #47
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Re: Which AIS antenna splitter

Quote:
Originally Posted by rabbi View Post
I have no clue about the theoretical details but:
When adding the AIS transponder I installed a splitter because I was too lazy to route cables and go up the mast. It was an "easyAIS OCB", not cheap @180 Euro.

Guess what: After a few weeks I bought a short AIS rubber antenna and mounted it on the spreaders.

Much better reception.

In my particular case the reception quality was barely OK with the chartplotter only. But it dropped massively when the OpenCPN PC was switched on, too.
The EasySplit OCB splitter website and documentation gives no specification on Rx or Tx insertion losses. It is possible that your results were due to it being a bad quality splitter (I wouldn't go on price for determining quality).

Your last sentence doesn't make sense. The chart plotter or computer device connected to the NMEA output stream has no relation to the reception quality of the unit itself. There is no interaction there, and no possible way they could interact. It is possible that the NMEA output wiring was done poorly and the AIS unit worked fine, but its output could not be read.

Mark
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Old 16-12-2015, 11:08   #48
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Re: Which AIS antenna splitter

Mike,
Unfortunately I haven't been successful in explaining my view here... sorry...
Quote:
Originally Posted by MikeFergie View Post
Okay so we have some for and against on splitters.
But, to be clear, I am not "against" splitters....But..
But, I am "against" blanket recommendations "for" them!!
And, this is why I agreed with Bill!!

Myself, and some others, have looked closely at both the additional losses introduced into the system, and at the potential issues arising from a failure...and we understand both the technical details, and the odds of possibly failure....and have also taken into account "where" and "how" we are sailing, etc.....
And, we've all made our decisions based on all of these factors....

If you read my earlier posts here, you'll see why I made my decision to use a Vesper SP-160 splitter....
BUT...

But, if you look at the original question from the OP, you'll see that Bill recommended against him using a splitter....
And, because of both the lack of the OP's understanding of the details here, and the lack of necessity for most sailors to use a splitter....this is why I agreed completely with Bill...

Again, I'm not "against" splitters....but unless the sailor is well informed and understands this situation completely, a blanket recommendation "for" splitters is (in my opinion) bad engineering and bad seamanship....




BTW, Mike, I assume you know this...but just in case....
I do hope you have a modern Class D VHF-DSC-FM Radiotelephone....and have GPS position data connected to it...And, for communications / distress signaling beyond VHF range, you may wish to fully understand the GMDSS, as well as MF/HF-DSC, INMARSAT-C...as well as your EPIRB...

And, as far as EPIRB's....here's some info for you all...
Enjoy.
EPIRB Activation? What happens/How to improve rescue odds



I do hope this helps...

Fair winds...

John
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Old 16-12-2015, 11:21   #49
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Which AIS antenna splitter

John,

Please explain the "failure modes" the rest of us can't understand.
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Old 16-12-2015, 11:21   #50
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Re: Which AIS antenna splitter

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Originally Posted by colemj View Post
The EasySplit OCB splitter website and documentation gives no specification on Rx or Tx insertion losses. It is possible that your results were due to it being a bad quality splitter (I wouldn't go on price for determining quality).
When introduced it was advertised as "lossless" but that was removed later. I remember it received some attention at least in germany and had some pretty good tests.

Quote:
Originally Posted by colemj View Post
Your last sentence doesn't make sense. The chart plotter or computer device connected to the NMEA output stream has no relation to the reception quality of the unit itself. There is no interaction there, and no possible way they could interact. It is possible that the NMEA output wiring was done poorly and the AIS unit worked fine, but its output could not be read.
Mark
I know there is no direct connection between PC an splitter but somehow it was really the case:
The chartplotter is connected to the AIS via NMEA and the PC is connected to the AIS via USB. Somehow the PC introduced some kind of noise into the system that made its way to the splitter and caused trouble.

With both chartplotter and PC switched on the the maximum distance was around 5-7nm for class A (so strong signals I reckon). With the PC switched off one could immediately see some targets further away, like a number of class A targets all lying in a harbour 12nm away. PC on again and they disappeared.


I tried it several times and the result was always the same. PC off: targets appear, PC on: targets disappear
Maybe the combination of AIS transponder and splitter is to blame (and of course the PC for making the noise in the first place).

But as soon as I moved to a separate antenna this problem was gone. AIS range is stable regardles of PC on or off.

I even gave the splitteranother try on the new rubber antenna at the spreaders. Same result: If the PC was switched on it reduced the AIS range by around 50%.

Believe me, I was completely willing to make this splitter thing work as routing cables is a nightmare on a Mahe. But no way I could live with a 5nm AIS range (I used to have at least 30nm for Class A targets in my last boat).


Edit: EasyAIS is a well known brand here and highly though of. I could sell that damn thing on ebay for 3/4 of the purchase price so no big loss. At the end the second antenna was cheaper, simpler and more reliable.

I am not saying that all splitters are made equal. Others may be immune to these problems. But why take the risk and introduce another component that can only cause issues?
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Old 16-12-2015, 11:48   #51
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Re: Which AIS antenna splitter

Can we at least say that in an ideal situation, everything would have a fat, low loss coax as short as possible with no additional connecters and connected to an antenna that was tuned specifically to that frequency range and ideally mounted.
That's the ideal, sometimes that isn't either possible or more trouble than we want to go through, and that is why some of us use splitters, God forbid, but I bet some of use are even using a splitter to connect an FM radio so we can listen to music.

Any break in the coax and and additional components bring on additional failure points and almost certainly signal loss.

Most of us are not Amateur radio aficionados and can live with a little less than optimum performance, just like I bet if some of you racers come along with me on my boat, I'd drive you nuts by not having my sails properly trimmed.
My radio installation would drive a radio expert nuts too, I'm certain, I'll fix many of the issues when the mast is stepped, but I ain't pulling coax until then.
I'm OK with "Good Enough"
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Old 16-12-2015, 11:55   #52
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Re: Which AIS antenna splitter

Dan,
Only got a few minutes...
Quote:
Originally Posted by transmitterdan View Post
John,

Please explain the "failure modes" the rest of us can't understand.
The most common failures would be:
--- "dead"....i.e. the SP-160 would be in its "fail safe" position, allowing the VHF access to the antenna...but not the AIS....
(this is what you get if 12vdc power is lost to the SP-160, as well...)

--- blown pre-amp (which I have seen a LOT in land-based two-way radio and amateur service, from close lightning strikes! and other causes)....this is actually more common than you might realize, in areas with electrical storm activity...
This would not effect the VHF radio, but would most likely render your AIS reception dead....(although AIS transmission should still work...)


Next, would be blown/dirty contacts....adding additional loss thru it....on either VHF radio or AIS, or both...
And, this would probably go unnoticed by most sailors....especially if just a gradual reduction in performance....but, could also be caused by a close lightning strike...

Also about as likely would be a switching failure, meaning the unit is stuck passing only one unit's signal thru to the antenna (VHF or AIS....)


Another failure mode is pre-amp induced (and/or pre-amp exasperated) IMD, rendering your AIS reception unusable....this is most likely to occur in crowded areas, with lots of ship traffic (exactly where/when many sailors would want their AIS working its best!!)


Another failure mode could be pre-amp oscillation (rare), or pre-amp overload....which, in addition to wiping out your AIS reception, could also render your VHF reception unusable...



Now, before anyone throws a flag here.....please allow me to make two things absolutely clear:
1- I have personally seen / experienced ALL of the above failures (including multiple close lightning strikes) to some of my personal land-based equipment, as well as equipment that I was responsible to maintaining/repair (amateur radio, two-way VHF and UHF business radio, broadcast systems, etc.), on shore....not on-board my boat!!
(and have worked with dozens of RF engineers over the past 30+ years who have also had these failures....Central Florida summertime is a bitch of a place...)

2- I have never experienced a failure of my Vesper SP-160, nor do I know of anyone that has....


{I've also taken a direct lightning strike to my measthead in Aug 2006...blew out some things, but couldn't trust any of it, so did a complete electronics upgrade/refit in fall of 2006....
And a direct strike to my ham tower at home, only blew out the one thing that I didn't disconnect, an FM stereo tuner/amp....
But, every year I take a few hundred direct strikes to the tower that I have two of my VHF ham repeaters on....and every few years, suffer some minor damage, due mostly to good grounding!!}



There are probably more "failure modes", but those above are the ones that I considered....
And, of course understand my earlier comment about using a lower loss coax, to compensate for the loss introduced by the SP-160...


I hope this answers your question...

Fair winds..

John
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Old 16-12-2015, 12:06   #53
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Re: Which AIS antenna splitter

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Originally Posted by a64pilot View Post
Most of us are not Amateur radio aficionados and can live with a little less than optimum performance, just like I bet if some of you racers come along with me on my boat, I'd drive you nuts by not having my sails properly trimmed.
My radio installation would drive a radio expert nuts too, I'm certain, I'll fix many of the issues when the mast is stepped, but I ain't pulling coax until then.
I'm OK with "Good Enough"
I'm "good enough" at driving any kind of expert nuts, too
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Old 16-12-2015, 12:07   #54
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Re: Which AIS antenna splitter

A64,
Two quick points...

1) The paranoia over "too many connectors" or the "wrong type of connectors", has gotten absurd!!
This has been proven wrong by me and others over the years....(I even posted a photo showing a total of only 0.5db loss thru 23 different connectors/adapters!!!)

Quote:
Originally Posted by a64pilot View Post
My radio installation would drive a radio expert nuts too, I'm certain, I'll fix many of the issues when the mast is stepped, but I ain't pulling coax until then.
I'm OK with "Good Enough"
2) I'm not sure if I can speak for Bill....but, for me a sailor who is thinking that "good enough" is in fact good enough for their VHF radio system, is looking at things short-sidedly....


The VHF radio system is the primary means of maritime comms, collision avoidance, weather, safety, etc....and, in my opinion, any sailor who voluntarily places more emphasis on their cell phone, Wi-Fi, etc., and not their VHF system is doing themselves a disservice...
I'm sure you're not one of them!!!

But, I stand behind my words, that "blanket" recommendations of most things technical are usually bad engineering and bad seamanship....
And, here in this discussion about AIS antenna splitters, a "blanket" recommendation "for" them, is, in my opinion, just that: "bad engineering" and "bad seamanship"...



Fair winds..

John
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Old 16-12-2015, 12:15   #55
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Re: Which AIS antenna splitter

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Originally Posted by ka4wja View Post
But, to be clear, I am not "against" splitters....But..
But, I am "against" blanket recommendations "for" them!!
And, this is why I agreed with Bill!!
Nobody here has made a blanket recommendation "for" splitters. If you are implying that I have, you did not read my very first response to the OP, nor did you read a subsequent post where I specifically made this clear.

Bill did make a blanket summary recommendation "against" splitters. Is he a bad engineer and a bad seaman?

So you are both "not against" them, and "against" them?

The failure modes you list later are just general failure modes of electronics - radios in particular - and many of them have to do with components that are not even part of a splitter (a preamp?).

All but one of them results in ensuring the VHF still operates, so the continued fear about putting ones VHF safety in jeopardy is strange. The other one is a nebulous "preamp oscillation" that leaves both radios open. That one is pretty much a fantasy - it will have nothing to do with a splitter failure, and has never been recorded EVER in a splitter.

And almost all of them rely on a lightning strike so surgically precise that it does not take out any other components, while going unnoticed by the user.

You and Bill can ignore responding to me all you like, but since you two have considerable expertise in these things and are looked upon for advice, I will hold your feet to the fire when you are lazy or relying on unexamined beliefs or out-dated technology. Which both of you are doing in this example.

It is best I can do for non-experts here who are trying to make decisions and weigh advice.

Mark
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Old 16-12-2015, 12:18   #56
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Re: Which AIS antenna splitter

John,
I am no where near the exert you are, but I do know that every connection is an opportunity to be a bad connection, maybe a cold solder joint, or oxidation in a crimp and even another place where the environmental shield for the coax is compromised. Done right, I'm sure your correct, but how many connections have you seen done wrong? All I'm saying is in an ideal lab type of world, they wouldn't be there is all, and my boat is far from that lab.

Good enough for me is using the automated Seatow radio check that plays your transmission back to you, if I'm a significant distance away, but the play back is clean and clear, to me that is good enough, I don't know how exactly, but I do know that a good mike and or something done to that circuitry can boost what we used to call modulation and make a radio sound a whole lot better.
My Vesper reports that I have a high SWR, so I know my system needs work, mast is coming down in a year or so and it will go back up with new coax and antenna, I think what I have is 27 yrs old. It still had the original radio in it when I bought the boat.
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Old 16-12-2015, 12:18   #57
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Re: Which AIS antenna splitter

Here is a blanket recommendation. Buy the Vesper SP-160, and move on. Do you still have to decide on an AIS unit as well? Oh, and whether to use your current VHF antenna, or one of the special antennas that Vesper sell that are tuned between the AIS and VHF frequency? I've got the Vesper splitter, the Vesper VHF/AIS antenna, and the Vesper XB8000 - and all of them work fantastic. Antenna at the top of a 53 ft mast.
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Old 16-12-2015, 12:19   #58
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Re: Which AIS antenna splitter

Quote:
Originally Posted by ka4wja View Post
1) The paranoia over "too many connectors" or the "wrong type of connectors", has gotten absurd!!
This has been proven wrong by me and others over the years....(I even posted a photo showing a total of only 0.5db loss thru 23 different connectors/adapters!!!)
But you and Bill have both put forth the argument on this thread that the inclusion of two extra connectors in using a splitter puts the VHF safety at risk and is bad engineering practice. You even implied that a barrel connector, to be used in the event of a splitter failure to join a split VHF cable, was risky because of "possible corrosion".

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Old 16-12-2015, 12:26   #59
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Re: Which AIS antenna splitter

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The VHF radio system is the primary means of maritime comms, collision avoidance, weather, safety, etc....and, in my opinion, any sailor who voluntarily places more emphasis on their cell phone, Wi-Fi, etc., and not their VHF system is doing themselves a disservice...
I'm sure you're not one of them!!!
I don't consider my VHF as the primary means of collision avoidance (eyeballs, AIS and radar are better at that). To me VHF is only a last resort if I failed to keep me out of trouble (and most often not helpful then, as folks who ignore rules of way typically also don't monitor their VHF).

Also I don't really use VHF for weather: my computer is better at that as I can get the VHF forecast in writing, retrieve navtex messages when nearshore and GRIBs / IAC / weatherfax when offshore

For me the VHF is simply a safety device when near shore and a short range communication tool.
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Old 16-12-2015, 20:41   #60
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Re: Which AIS antenna splitter

OP here and I have given up on a splitter

Any comments on a combo AIS/GPS antenna as this looks like an easy, cost effective solution

Tram Combo VHF/GPS 39 inch Antenna

Digital Yacht GV30 VHF AIS GPS Combo Antenna | eBay
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