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Old 17-12-2015, 05:21   #61
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Re: Which AIS antenna splitter

Some AIS units come with an external GPS antenna, so you wouldn't need another one.

Other AIS units have an internal GPS, and you would only need an external one if your mounting location for the AIS is blocked by metal.

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Old 17-12-2015, 08:11   #62
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Re: Which AIS antenna splitter

And these combo antennas don't save the biggest headache which is running 2 cables as each antenna still has its own cable.

Another thing to consider is whether you want to have all your eggs in that one basket. There are probably better AIS transmit/receive antennas than either of these. They look to be fairly short and inefficient. Suspiciously I could not see any specifications for VSWR or gain in the marine VHF band and particularly on the higher AIS frequency.

The Vesper AIS antenna is a good choice for a dedicated AIS antenna. It also works well at normal marine VHF frequencies. I agree with Mark, all "good" AIS units will come with their own GPS antenna and some may even insist that you use it for specified performance.
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Old 17-12-2015, 08:20   #63
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Re: Which AIS antenna splitter

Quote:
Originally Posted by colemj View Post
Some AIS units come with an external GPS antenna, so you wouldn't need another one.

Other AIS units have an internal GPS, and you would only need an external one if your mounting location for the AIS is blocked by metal.

Mark
Even then I'd give it a try before going the external antenna route, my Vesper is mounted directly under my VHF so I was sure I'd need an external antenna, but it tracks satellites fine without one.
My old boat was stored inside of a metal aircraft hangar and the 740S was installed under a metal T top, but even inside of a closed metal building the thing tracked satellites with only a little degradation, newer GPS's are phenomenal.
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Old 20-12-2015, 18:25   #64
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Re: Which AIS antenna splitter

Mark,
1) First off, please accept my sincere apologies for misunderstanding what you wrote earlier!
When I read your fervent post, stating your adamant disagreement with Bill's seaman-like recommendation, I understood you to be making a blanket recommendation "for" the use of a "splitter".
But, now I see that you actually do agree with me, that every individual sailor should understand exactly what they are dealing with, and how these devices may effect things, and that they should be given the facts / knowledge in order to make decisions (as you and I have done).
{In my own defense of my misunderstanding, remember that at that time, none of us knew what the original poster's precise need was, nor exactly what his current VHF system consisted of, state of the cable/connectors, etc....nor even more importantly whether he understood the technical specifications, nor how they may effect his system, nor whether he understood the various possible issues a "failure" could cause, etc.....so...
So, I misunderstood you, in that I that I assumed that you were making a blanket recommendation "for" using a splitter...sorry about that!!}

Quote:
Originally Posted by colemj View Post
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?
It appears that you were taking issue with Bill's posting, where you interpreted him to be making a blanket recommendation "against" splitters.
Where as, I interpreted Bill to be giving seaman-like advice to an unknown sailor on the internet, that there are too many variables / technical details for the average sailor to understand, and therefore because of this, he was advising this unknown sailor to install a second VHF antenna (on the stern rail, bimini top, arch, etc,), and use this as his AIS transponder antenna.
Which is why I wrote: "in general I agree with Bill here....for most cruisers, his advice/recommendations are good..."

So, again, please accept my apologies for the misunderstanding.....that's one of the problems discussing tech stuff on-line....but, no worries!!




2) Secondly, the above notwithstanding, I would like to politely take issue with you calling me a liar and then further insulting me by calling me lazy...
Quote:
Originally Posted by colemj View Post
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.

Mark
Mark, I do not know you and you do not know me, and in polite society this kind of unprovoked and unsubstantiated attack is quite rude and in all honesty disturbing to me....(if I knew you personally, I'd have given you a call and asked if you were okay, and was there anything I could do to help...perhaps take you out to lunch...we got good BBQ down here!

Since I do not know you, I'm left wondering what to do....

And, here is what I decided...
I'll just post a few personal facts from my life, politely ask you to believe / understand that this IS the truth...and hopefully you'll simply accept this as fact and apologize to me for calling me a liar and lazy...

a) I wrote earlier that I do not know of any SP-160 failures, and I have had nomissues withn my SP-160....but I have personally experienced "splitter" failures, pre-amp failures, relay failures, etc....and most have NOT been caused by lightning strikes, certainly not by direct strikes...


b) You write that splitters and relays do not fail, and especially when you write that pre-amps do not fail, EVER, when I just got done writing that I HAVE had them ALL fail in multiple ways, yes, even pre-amps oscillating (causing blocking of the receivers connected to them)....

[BTW, the Vesper SP-160 does have a pre-amp in it....as does the other "zero-loss" splitter....oh, and please understand that what everyone here is calling a "splitter" is in fact a "relay/splitter" combination, and the SP-160 (and the other "AIS splitters" that have pre-amps in them) is a "relay/splitter/pre-amp" combination....
Do you really think I was posting about things that are not true??? (ah, yes you did....because you called me a liar...)
Seriously, sir, it seems you are not as informed as you thought...]

So, if you care to read this truth, in more than 30 years in communications (some of these failures just this past couple years, with modern 21st Century devices, not "ancient history"):

--- I HAVE personally had 2-way transmit and receive relays and splitters fail, in multiple ways....VHF/UHF cross-band couplers (2-way freq-dependent transmit and receive splitters) fail....in-band receiver multi-couplers (2-way, 4-way, and 8-way, receive splitters) fail....all from either close lightning strikes, or from direct lightning strikes....
Some of these are on my own personal tower at home, some are on my broadcast tower, some have been on others' towers...
{please take note, in the many 100's of direct strikes my equipment has experienced every year, for many years now....I have had VERY FEW actual failures!!! The broadcast tower (1368' high) where I have some of my own equipment, is struck many 100's of times each year (i should write 1000's of times, but some years it's been only a bit over a 1000....so, I'm being conservative here...)}


--- I have also had T/R relay or RF-sense relay failures....sometimes just burnt contacts from lightning arc-overs, but sometimes just a failure over all...


--- Also, as for "pre-amp" failure....well to say that it happens often would be an overstatement of course (and I never wrote that it happens often)....but it does happen...
Since I end up fixing some of the pricey ones myself, I am very familiar with these....here is a a list off the top of my head....
I have personally had receive pre-amps fail....you may be surprised to learn that the "total dead" failures were usually the result of close lightning strikes, not direct strikes....(btw the broadcast tower has a "counter" that trips for each direct strike, so I have some pretty hard facts here!).....
I have also personally seen others with similar commercial and amateur VHF and UHF pre-amp failures....

Also, I have personally had both a D432 vhf pre-amp and a MGF1312 vhf pre-amp, oscillate, and block / wipe out the receiver connected to it (meaning that it's oscillation was so strong that the receiver was being blocked from receiving any other signals....note that this is sometimes confused with "overloading", but it isn't the same thing.....and, although "overloading" is getting rare these days in VHF systems, it does also occur...)
As well as have personally seen others with similar commercial VHF and UHF pre-amp oscillations...
These are usually caused by devices going out of tolerance....and/or junction issues....not from lightning strikes (whether direct or close)...
But, whatever the cause, it does happen!!!

Also, there are numerous times when you generate receive IMD from the pre-amp....and while this usually only happens in RF crowded environs......this describes harbor areas and in/near heavy ship-traffic areas, with numerous VHF (and AIS) transmissions....

Gosh, there are many more personal experiences I could list.....but, I think I've been specific enough to prove that I'm no liar!!! (btw, I do have a blown cross-band coupler, still sitting under my desk at home....and if ya' send me about $250 - $300 cash, I'll send it to you as physical proof...


c) As for being "lazy"....
Well, since I'm the only one caring for my 94 yr old Mom, as well as still working/consulting part time, as well as attempting to have a tiny bit of a social life, and I do still get out and sail.....I find this comment to be quite rude as well...

And, specifically this week, where I have been dealing with my Mom's doctors' appointments / diagnosis.....her primary physician, oncologist, and surgeon.....all this past week....(her appointment with the surgeon is tomorrow)...
To say that all of this has taken some of my time is an understatement....not to mention that I've spent a great deal of my spare time with her, taking her mind off her diagnosis / surgery....and I'm NOT complaining at all....heck some of this "quality time" is us watching Miami Dolphins football, so it's not really a big deal...
And, I love my Mom....my parents taught me about sailing, voyaging, cruising, adventure, etc. during the 60's and 70's....my Dad taught me celestial nav, and they both taught me to admire / respect others, especially those of different cultures/backgrounds...in our cruises when I was a kid in the 1960's, we did everything that everyone does now a days, times 10!! Including......................................... .......................
Why bother listing it all....you'd probably call me a liar anyway.....(hey, we weren't the Dashews or Pardeys, but damn few others were out there doing it in the 60's....nuf said!)

Sorry, for the digression....But, to write that I'm "lazy"??
Well, that is just out-n-out rude and insulting to me and my family!!


d) As for me implying that a sailor's spare PL-258 barrel would be corroded....sorry, but that is NOT what I meant....just listing this as information/knowledge to be aware of, before making a decision on use of an AIS "splitter"....
Quote:
Originally Posted by colemj View Post
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".

Mark
What I mean is that if you choose to keep one handy (in case of a "splitter failure"), then you should keep it clean and dry....(not sure how that was misunderstood...but, sorry about that!)


e) And, as for me commenting on "connectors".....
I'm the one here who has been realistic about the miniscule amount of connector loss!!!
Have you not seen the photo???
Vesper AIS SP-160 "relay/splitter" test results, lab/real world

I have NEVER written, NOR EVER implied that the addition of two extra connectors (on the "splitter" or otherwise), introduces any measurable losses at all!!!!!!!!!!!!!!!!!!!!!!
Here again, you are further insulting me....



I do not expect a nice brief apology, and I have decided to just unsubscribe from this thread, and never return to it.....so, no need to try to impress me with any semantic argument, etc., I'm done here, and wish the original poster all my best...(and Merry Christmas!)
Rather, I just wanted to make it clear to you all that I'm neither a liar, nor lazy!




3) As for others not considering their VHF as part of their collision avoidance system.....I think this is just a language issue....as I fully understand the ColRegs and have been doing collision avoidance for > 40 years....
I think we agree, as it is part of the safety system, and used for short-range comms....here on this side of the Atlantic (as well as crossing the Atlantic), it is used for communications to coordinate crossing/passing situations (what I generically called "collision avoidance"), etc....
Just a different choice of words....no worries!



4) As for VHF antennas and their VSWR....have you looked at the sweep/scan of my masthead-mounted, 1/2-wave, 3' Shakespeare end-fed SS whip???
It's right there in this thread....have a look....(if I get the time, I'll test my bimini-height, stern-rail mounted antenna, and post the results there as well...)
Vesper AIS SP-160 "relay/splitter" test results, lab/real world


And, have you read the links I posted right here, in this post???
Which AIS antenna splitter



Fair winds...

John
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Old 21-12-2015, 06:37   #65
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Re: Which AIS antenna splitter

Please point out where I called you a "liar".

Please point out where I said a splitter will never fail. In this case, all I ever wrote was that all failure modes are such that they fail over to the VHF - thus do not put its safety in jeopardy.

It takes extreme sensitivity to conflate my calling your intellectual reasoning in this particular topic "lazy" with physical laziness or laziness in life in general. Take all the offense you want, but it is disingenuous and transparent. The same goes for your manufactured "liar" claim.

The "preamp" in a splitter is vastly different in design and intended terminology than a transceiver preamp in a radio. Conflating the two is intellectually lazy and does a disservice to those who rely on your expertise in making decisions.

You are making my point regarding the connectors- earlier you gave a reason against using a splitter because of the extra connections being a risk. Bill did also.

Bill made a summary blanket recommendation against splitters in all cases. There is no other way to interpret his post and its follow up. Others can read into it as they like.

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Old 21-12-2015, 07:00   #66
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Re: Which AIS antenna splitter

Regarding preamp failure it seems there is little or no history of AIS splitter failure so John falls back on his experience with failure of other preamps. The preamps used in most AIS splitters are fairly low gain. Typically we see gains of 10dB or less. It is much easier to protect a low gain preamp from nearby lightning impulses than a high gain 30dB preamp used in TV antennas or cellular base stations.

A direct or close lightning strike will probably damage a splitter but it just as likely will destroy the VHF receiver too. So I think a lot of fretting about lightning induced preamp failure is not warranted until we see some actual data. If you are paranoid about this issue then look into lightning protection devices such as Polyphaser make. They work about half the time but are no guarantee of success. And the small VHF antennas we use on boats are easily destroyed by lightning. So having a spare antenna stored somewhere is a good idea as is having a VHF barrel connector (female-female) to bypass the splitter.

Fortunately AIS uses a constant envelope modulation format known as GMSK. That means that it is nearly immune to inter modulation distortion (IMD). You could run the AIS signal through a diode clipper and create tons of IMD but the receiver would decode the signal perfectly. This is just one of the benefits of constant envelope modulation formats such as GMSK and is probably the main reason it was selected. Linear amplifiers are not required to preserve the signal integrity of AIS.

I have seen no evidence or compelling argument that says the majority of sail boats with masthead antenna should avoid using "good" splitters. The reported experience of several users suggests that a splitter with low transmit loss and relatively modest receive gain should work well for most applications. I also have a hard time understanding how an AIS splitter can make a "bad" installation "worse".
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Old 21-12-2015, 07:23   #67
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Re: Which AIS antenna splitter

Quote:
Originally Posted by transmitterdan View Post
I also have a hard time understanding how an AIS splitter can make a "bad" installation "worse".

I struggle with the logic put forth here that the "typical cruiser" uses high-loss coax and makes high-loss connections to it - therefore they are better off mounting a separate AIS antenna down on a rail (using bad coax and connectors), which will just make their new system pretty much unusable.

At least good splitters come with pre-made cables and connectors, so the punters can't make them worse. Adding a splitter will only suffer from any pre-existing problems - not create whole new ones.

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Old 22-12-2015, 02:28   #68
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Re: Which AIS antenna splitter

I have installed the GME AIST120 transponder & the AISS120 Splitter & have found them to work well with my Raymarine a77 for cruising down the east coast of Oz.

When I first set them up, the AIS wouldn't work, but as it came with Pro-AIS software it was diagnosed as very high VSWR. After replacing / redoing all the existing VHF connectors at the mast base it all came up good. So a plus was I ended up improving the VHF radio at the same time.

However, with nothing else to compare them with & not being an electronics engineer I am wondering how the splitter rates compared to other splitters in this thread. You can see the specs here

It was much cheaper than the Vesper setups, so would appreciate any feedback on the performance specs of the GME units.

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Old 22-12-2015, 06:16   #69
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Re: Which AIS antenna splitter

Dave,

The specifications are good for AIS. Ideally one would like to see some gain on VHF and AIS receive but they elected to set the gain to unity. Nothing wrong with that though.

Alas, their marketing department has used the phrase "zero loss" which isn't exactly correct and leads to some misunderstanding. The loss in VHF transmit is <1dB according to their specification. Which is quite good for that particular specification but it is not zero loss.

Your AIS transponder is based on the SRT module which is widely used by several AIS brands. This module seems to have few problems based on the reports here on CF. The in-built VSWR measurement and warning system is very helpful in checking the cables, connectors and antenna. As you point out installing AIS may be the first time the VSWR of the antenna has been checked. Good on ya for paying attention to that important parameter.

What do these two units sell for in Oz?
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Old 22-12-2015, 09:21   #70
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Re: Which AIS antenna splitter

transmitterdan,

Thanks for your reply, much appreciated & makes me feel good about my decision.

The AIST120 Transponder is AU$549 & the AISS120 Splitter is AU$219.

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Old 22-12-2015, 15:01   #71
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Re: Which AIS antenna splitter

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Originally Posted by colemj View Post
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
First one that comes to mind !
https://www.gme.net.au/catalogue/nav...r/aiss120.aspx
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Old 22-12-2015, 16:12   #72
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Re: Which AIS antenna splitter

I couldn't find any actual specs on that unit, which should be a giant warning, but I suspect it is like the Sci-tex unit linked to earlier and has zero receive loss only, with a small tx loss like most.

For practical purposes, an insertion loss <1dB is zero loss. It won't be noticeable in use regardless how bad the existing system is. Even the "experts" here are wiring their radios with coax that has more loss than this - and they think nothing of doing that. And they are correct (on that point).

However, I would run away from anyone who isn't forthcoming with specs, or uses "zero loss" in their marketing.

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Old 22-12-2015, 16:32   #73
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Re: Which AIS antenna splitter

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Originally Posted by colemj View Post
I couldn't find any actual specs on that unit, which should be a giant warning, but I suspect it is like the Sci-tex unit linked to earlier and has zero receive loss only, with a small tx loss like most.
Mark,

The specifications are pretty good. See the link in this post: Which AIS antenna splitter
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Old 22-12-2015, 16:43   #74
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Re: Which AIS antenna splitter

What am I missing? Your link is back to this thread. I followed the link he gave, but I didn't see any specs on the website or any links to documentation.

So is it really zero loss Tx?

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Old 22-12-2015, 16:46   #75
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Re: Which AIS antenna splitter

The post has a link to the brochure:

https://www.gme.net.au/media/469538/AIS_b_web.pdf

which shows all the specifications.
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