Which AIS antenna splitter

[transmitterdan]

Originally Posted by colemj

Have you actually seen this? I haven't.

I have seen claims of 1dB transmission loss and some receive GAIN, but never seen one that said zero loss. In this case, actual measurements have born this claim out (see a previous link in this thread).

Can you point out a brand/model that claims zero loss?

Mark

Sadly there is at least one company using a marketing slogan of "zero loss splitter". It is not Vesper. Look up Si-Tex.

[colemj]

I looked it up. They claim zero loss on receive and <1dB on transmit.

This seems in line with other good splitters.

I do agree that their marketing could be misleading in this, though. The "headlines" state zero loss, but the spec sheet connected to them gives the details.

Mark

[ka4wja]

SailRedemption,
Sorry that I didn't write things better....poor choice of words / poor wording, on my part...

I never wanted to imply that a 1db loss thru a "splitter/relay" would be proximate cause of loss-of-life!
Sorry about that!!

What I was referring to was, an unnoticed "splitter failure" at the wrong moment could be a serious issue, where you may not know that your AIS is no longer sending out your position, and/or you are no longer receiving any AIS reports from others, and/or your VHF is no longer actually connected to the antenna, and can no longer transmit/receive, etc. etc.....
And if the sailor was relying on the AIS device as an "assist device" in watchstanding, rather just an assist in plotting/collision avoidance, or even if the sailor was doing the normal things, like relying on their VHF radio for their primary communications and safety device, and when needed to communicate / avoid collision / etc. you can no longer use it....
Well, those could have a very bad outcome....and in the worse case, perhaps loss-of-vessel / loss-of-life...

THIS is what I was referring to, in regards to my comments on these splitters being critical safety devices, and in my generic questions about whether a sailor was aware of / prepared for what could happen...


Again, please accept my apologies for not being more clear!

{and, btw....in my opinion, with the additional info you provided, YOU seem fully aware and prepared (as is Mark, myself, etc.), but the unfortunate facts are, that many sailors are not...and again, when you see some of the examples that I've seen, many done by "professionals", you'd understand my caution about "blanket recommendations"....}

Some examples, right off the top of my head:
A few years ago, I was asked by a old friend who knew I grew up sailing on my parent's Hinckley, (and knew I've been in the comm / electronics industry for 30 years), to have a look at the electronics on a brokerage Southwester, that had just had a complete electronics re-fit done by one of the biggest marine electronics firms in the Chesapeake, before leaving Annapolis and heading for Florida / Bahamas....they made it to Savannah, GA....they'd been using a handheld VHF in the cockpit, and their smartphone for GPS / navigation...
When I got there, the husband was all ready to get things fixed and get going, and was kinda a pain....but, his wife was a dream, she knew I was there as a favor to Hinckley (I do NOT do marine electronics for a living!)....
What did I find?
--- The VHF radio connected to a "long-wire" antenna....(black GTO-15 (which I hadn't seen in years, as all I use is white)
--- The SSB radio connected to the VHF antenna...(white RG-8x)
--- The WeFax sort-of connected to the SSB antenna....(black RG-213)
--- The depthsounder transducer wires were stripped / tinned, just like they come from the factory (?), but left sitting in the bilge...
--- The Raymarine wind and speed instruments worked, but not calibrated...and of course no depth...
--- The Raymarine radar working, but no NMEA data (or SeaTalk data) connected to it...
--- Autopilot no Seatalk / no NMEA, but did "work to some extent"...
And, many other things just never done / unfinished...
And, this was all done by licensed/insured/"factory-certified" pros!!

Or, how about some fellow sailors I met in Bahamas a couple years ago....with a fairly new boat (about $500k), with ~ 100' RG-58 for their VHF antenna (installed by the factory)....and their VHF radio powered thru small wires thru the breaker panel a ways away, and it dimmed its display when you transmitted.....a "few hundred dollar Wi-Fi gizmo", installed by their commissioning yard (which was an Alfa awsh036u, which should cost you $20), that they never got a "driver" for, so in the 2+ years they had it, they'd never been able to use it....and their list went on and on...

Or, the "friends" who bought a 3 year old boat, and the connectors had never been weather-proofed, and the coax was shot (water intrusion)....
I recommended they hire a pro, and have it all replaced....instead a "nice guy at west marine" sold them some new Shakespeare crimp connectors, and told 'em how-to use a "leatherman" tool to properly install these connectors....(no fooling!)

Or, how about the dozens and dozens of sailors I hear every week on the VHF whose radios are woefully underdeviated and almost impossible to hear....even though they are actually talking into the mic close enough and loud enough....(of course we are all aware of the opposite case where they scream into the mic....but, here we are talking about a radio and/or mic issue...)

Or, how about the 1000's of sailors who go to boat shows and believe all the advertising / marketing hype, for all these new wiz bang devices...they buy 'em, and never install/hook 'em up correctly, etc. etc.

No more rambling from me here...
My list here goes on and on....

Just trying to give a few examples of what I see / hear all the time....NOT trying to imply that Mark, SailRedemption, etc. fall into these groups at all!!!
Just saying that many sailors do...


But, here I think you've misunderstood what I wrote....you have LESS loss than you think!!
85' of your 9913F7 has only 1.5db of loss, plus the 1db loss thru the SP-160, your total is 2.5db....not 4.5db...so, you are well on the better side!!!!

Originally Posted by SailRedemption

"But, assuming you have taken care of all the above, and accept any issues that a splitter/relay might cause, then in my opinion, your use of the SP-160 is fine..."

Great, even with the 4.5dB loss I'm still on the better side of "most" of the cruisers you have seen. (:

Please see the bold-type here...

Originally Posted by ka4wja

9913F7's loss at 150mhz is spec'd at 1.8db/100'.....versus the typically used RG-8x's loss of 4.5db/100' (4.2 to 4.7, depending on what brand/model, as "RG-8x" has NO standard)....or versus the commonly recommended RG-213's loss of 2.7db/100'

In your application (85'), your coax loss is approx. 1.5db...versus 4db, if you were using 85' of Belden RG-8x....versus 2.3db, if you were using 85' of Belden RG-213....

For your 85' run:
1.5db of loss, for your 9913F7
2.3db of loss, for RG-213
4.0db of loss, for RG-8


So, if you add the approx 1db loss of the Vesper SP-160, to your system:
1.5db + 1.0db = 2.5db of total antenna system loss...putting you line with those with RG-213, and still 1.5db ahead of the those with RG-8x...

Fair winds...

John

[transmitterdan]

Frankly, I don't know when all this worry about splitter failure has arisen. Has there been a rash of splitter failures that I have not heard about? Surely if it was a big problem there would be some buzz about it here on CF.

So far as I know all AIS class B units report any high VSWR fault and if they cannot transmit for a certain period another fault is generated. So if the splitter fails in such a way that it cannot transmit AIS data then the AIS unit should generate an alarm. I don't think there is a high probability of an unknown AIS splitter failure. Are there any AIS class B units without VSWR fault reporting?

[btrayfors]

Some AIS transponders are very sensitive to high SWR. Mine is. Others have reported the same problem.

Here's a discussion (begin with post #12): http://www.cruisersforum.com/forums/...-132692-2.html

Bill
WA6CCA

[transmitterdan]

With too much VSWR the AIS signal may be distorted due to group delay and frequency response issues. So the industry has taken the approach to complain about VSWR. I don't see it as a problem but rather a feature. Poor installations with high VSWR should generate alarms IMO.

[SailRedemption]

Originally Posted by ka4wja

SailRedemption,
Sorry that I didn't write things better....poor choice of words / poor wording, on my part...

I never wanted to imply that a 1db loss thru a "splitter/relay" would be proximate cause of loss-of-life!
Sorry about that!!

What I was referring to was, an unnoticed "splitter failure" at the wrong moment could be a serious issue, where you may not know that your AIS is no longer sending out your position, and/or you are no longer receiving any AIS reports from others, and/or your VHF is no longer actually connected to the antenna, and can no longer transmit/receive, etc. etc.....
And if the sailor was relying on the AIS device as an "assist device" in watchstanding, rather just an assist in plotting/collision avoidance, or even if the sailor was doing the normal things, like relying on their VHF radio for their primary communications and safety device, and when needed to communicate / avoid collision / etc. you can no longer use it....
Well, those could have a very bad outcome....and in the worse case, perhaps loss-of-vessel / loss-of-life...

THIS is what I was referring to, in regards to my comments on these splitters being critical safety devices, and in my generic questions about whether a sailor was aware of / prepared for what could happen...


Again, please accept my apologies for not being more clear!

{and, btw....in my opinion, with the additional info you provided, YOU seem fully aware and prepared (as is Mark, myself, etc.), but the unfortunate facts are, that many sailors are not...and again, when you see some of the examples that I've seen, many done by "professionals", you'd understand my caution about "blanket recommendations"....}

Some examples, right off the top of my head:
A few years ago, I was asked by a old friend who knew I grew up sailing on my parent's Hinckley, (and knew I've been in the comm / electronics industry for 30 years), to have a look at the electronics on a brokerage Southwester, that had just had a complete electronics re-fit done by one of the biggest marine electronics firms in the Chesapeake, before leaving Annapolis and heading for Florida / Bahamas....they made it to Savannah, GA....they'd been using a handheld VHF in the cockpit, and their smartphone for GPS / navigation...
When I got there, the husband was all ready to get things fixed and get going, and was kinda a pain....but, his wife was a dream, she knew I was there as a favor to Hinckley (I do NOT do marine electronics for a living!)....
What did I find?
--- The VHF radio connected to a "long-wire" antenna....(black GTO-15 (which I hadn't seen in years, as all I use is white)
--- The SSB radio connected to the VHF antenna...(white RG-8x)
--- The WeFax sort-of connected to the SSB antenna....(black RG-213)
--- The depthsounder transducer wires were stripped / tinned, just like they come from the factory (?), but left sitting in the bilge...
--- The Raymarine wind and speed instruments worked, but not calibrated...and of course no depth...
--- The Raymarine radar working, but no NMEA data (or SeaTalk data) connected to it...
--- Autopilot no Seatalk / no NMEA, but did "work to some extent"...
And, many other things just never done / unfinished...
And, this was all done by licensed/insured/"factory-certified" pros!!

Or, how about some fellow sailors I met in Bahamas a couple years ago....with a fairly new boat (about $500k), with ~ 100' RG-58 for their VHF antenna (installed by the factory)....and their VHF radio powered thru small wires thru the breaker panel a ways away, and it dimmed its display when you transmitted.....a "few hundred dollar Wi-Fi gizmo", installed by their commissioning yard (which was an Alfa awsh036u, which should cost you $20), that they never got a "driver" for, so in the 2+ years they had it, they'd never been able to use it....and their list went on and on...

Or, the "friends" who bought a 3 year old boat, and the connectors had never been weather-proofed, and the coax was shot (water intrusion)....
I recommended they hire a pro, and have it all replaced....instead a "nice guy at west marine" sold them some new Shakespeare crimp connectors, and told 'em how-to use a "leatherman" tool to properly install these connectors....(no fooling!)

Or, how about the dozens and dozens of sailors I hear every week on the VHF whose radios are woefully underdeviated and almost impossible to hear....even though they are actually talking into the mic close enough and loud enough....(of course we are all aware of the opposite case where they scream into the mic....but, here we are talking about a radio and/or mic issue...)

Or, how about the 1000's of sailors who go to boat shows and believe all the advertising / marketing hype, for all these new wiz bang devices...they buy 'em, and never install/hook 'em up correctly, etc. etc.

No more rambling from me here...
My list here goes on and on....

Just trying to give a few examples of what I see / hear all the time....NOT trying to imply that Mark, SailRedemption, etc. fall into these groups at all!!!
Just saying that many sailors do...


But, here I think you've misunderstood what I wrote....you have LESS loss than you think!!
85' of your 9913F7 has only 1.5db of loss, plus the 1db loss thru the SP-160, your total is 2.5db....not 4.5db...so, you are well on the better side!!!!
Please see the bold-type here...





Fair winds...

John

Hey no worries! Thanks, I'm a 2nd mate unlimited not a engineer like my fiancee, so I got confused with all the numbers Haha! Also, I may be radio licensed but I'm no radio tech. I just use the equipment, but I do follow good instruction from knowledgeable people both here and otherwise.

Thanks again for the help.. I do try not to be a statistic, or at least a bad one. My parents told me if you're going to do something, do it right the first time.

See more @ redemptiverepair.com

[btrayfors]

Originally Posted by transmitterdan

With too much VSWR the AIS signal may be distorted due to group delay and frequency response issues. So the industry has taken the approach to complain about VSWR. I don't see it as a problem but rather a feature. Poor installations with high VSWR should generate alarms IMO.

Yeah, maybe, but the fact is they don't. At least some don't.

How many cruisers do you know who have the knowledge and necessary equipment to accurately measure VSWR as seen by their AIS transponder?

I think we can't automatically conclude that the main VHF antenna with an installed splitter will necessarily present a low VSWR both at marine VHF/FM frequencies (nominally 156-158mHz) AND at the frequencies used for AIS (~160mHz).

And, if they're using a splitter, and have a high SWR how many have the means to adjust VSWR to a low value?

While I've never seen a circuit diagram of my AIS transponder, it acts very much like there's a signal clamp -- as is found in most modern SSB radios -- that reduces transmit power when faced with a high SWR. But, to my knowledge there's no warning of a high SWR condition.

As noted in the referenced thread (above), once I trimmed the dedicated AIS antenna for minimum SWR at the transponder, all was well and has remained so for over a year in all kinds of inclement weather, at dockside, at anchor, and at sea.

From this experience, and from observations of other knowledgeable tech folks, I conclude that achieving a low VSWR is a very important AIS installation goal....at least with some AIS units.

Bill

[transmitterdan]

I have not played with many AIS transponders. The Em-Trak (aka Raymarine) unit measures VSWR and provides the numerical result using their PC based setup software. It also lights a fault LED when the VSWR is high as I recall.

I think several brands are based on the same internal SRT core (AIS Class B Transceiver - SRT Marine TechnologySRT Marine Technology) so others may have the same feature set.

As to antennas I think Vesper make a pretty good simple whip antenna that is fairly broadly tuned to cover the AIS frequencies. Many antennas that came along before AIS are not optimized for the AIS channels so that is definitely a problem. But the problem is the same with or without a splitter. In fact, a splitter might help reduce slightly the VSWR due to a bad antenna.

[colemj]

The Vesper AIS units also clearly show a numerical and color-coded VSWR on their displays, as well as their computer (Mac and PC) and tablet/phone applications. In addition, they light fault LED's on the unit itself, as well as give alarms on any display/software when the VSWR is high.

I have tried our Vesper with four different common VHF 3' whips and all antenna gave VSWR<1.5 (all but one were 1:1, and the outlier was 1:1.3).

So maybe the takeaway is to also choose a good quality AIS as you would a good quality splitter?

Mark

[colemj]

I too would like to see any example of one of the quality splitters failing, in particular, failing in a way that left the VHF inoperable or degraded (where it would have stayed operable and unchanged without a splitter - ie. no lightning strikes).

Heck, I would settle for just one person stepping up and giving a single reasonable failure mode where this could happen (no surgically precise lightning strikes, please). Even if that failure mode is only theoretically possible. I keep asking this from the fear mongers, but I get no response.

Else wise, it is pure and simple fear-mongering and the argument is a logical fallacy. Perpetuating this is bad form.

The argument that one shouldn't use a splitter because lots of boats have poorly installed VHF systems contains several logical fallacies, as well as being a non-sequiter, but let's ignore that for the above.

Mark

[colemj]

OK, so I did a Google search for AIS splitter failures. I found NO references to failures of any type. I only found references where people were advocating against splitters for the same illogical and fear-mongering reasons given in this thread (this thread was actually one of the references).

The closest I found was an article by Doug Miller of Milltech Marine (a very well-respected person in this field) that stated they have "sold thousands" of splitters and have only had 2 returned for failure. The failure mode on those two units was a direct lighting strike.

He also said the following about people posting on web forums that adding a splitter is a bad thing: "Yes, I have read the same stories and it has been a frustration for us for several years."

He goes on about the height compromise in not using a splitter: "I also find the performance with the splitter using the single MV158 antenna on the top of my mast far exceeds the performance I have found with using the same antenna as a dedicated AIS antenna on the stern rail (antenna height and positioning clear of other metal interference objects is everything)"

In case one wants to make the argument that he sells splitters and has an interest in defending them (and anyone doing so about Doug Miller should be ashamed of themselves), keep in mind that he also sells dedicated AIS antennas - which cost as much as splitters. In other words, he wins financially either way.

Make of this what you will…

http://www.milltechmarine.com/Antenn...r-not_b_1.html

Mark

[MikeFergie]

Okay so we have some for and against on splitters.

I think a lot has to do with location as well. In my region of the world you could call for help all day on the vhf radio and not receive one reply (mozambique). Therefore for me the vhf is just here to tick the box. Ais is a more important feature as I see ships on my MDF long before i "see" them in particular at night which is what gives me comfort.

I use a raymarine splitter.

For safety and life saving I carry a SPOT and Sat phone and obviously an Epirb.

Sending sms's from a sat phone is far easier than trying to deal with radios which at the best of times are temperamental and I have no interest in trying to be a radio guru.


Is there someone that can perhaps list the splitters in order of best to worst for those of us that chose "simple" ?

Rgards
MikeF




Sent from my iPad using Cruisers Sailing Forum

[transmitterdan]

What you want to look for is a splitter with very little attenuation on the VHF transmit mode. "Bad" splitters have 2-4dB attenuation in VHF mode. "Good" splitters have <1.5dB attenuation in VHF mode. Next is the specification for attenuation in AIS transmit mode. Ideally this would be same or better than the VHF mode.

The next specification to look at is the attenuation in VHF and AIS receive mode. A "good" splitter will have either 0dB attenuation or even some gain such as +3-6dB of gain. A "bad" splitter will have -3-6dB attenuation in receive mode.

See if you can find these numbers for your Raymarine unit and post them. We can see how they compare to the "good" specifications.

Lastly, the power consumption is worth a look. I think most AIS units consume low power but it's a good idea to check this because AIS will be on 24/7 on most boats.

[colemj]

Vesper, Navico and Sci-Tex fit transmitterdan's criteria (sorry Dan, but that Sci-Tex looks pretty good once you get past the marketing fog). There is also another in that Doug Miller article I linked to above, but I forget what brand it was.

Mark