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Old 13-12-2015, 00:41   #16
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Re: Which AIS antenna splitter

Quote:
Originally Posted by ka4wja View Post
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
So what you're saying is that if I have a good masthead antenna (Gam SS-2), good cable (Belden 9913F7 x 85') with good connectors (Amphenol 083-1SP), and a new Standard Horizon 2150 radio I shouldn't use the Vesper splitter because it will adversely affect my VHF system?

Honest question.

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Old 13-12-2015, 05:20   #17
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Re: Which AIS antenna splitter

Sorry John, that argument makes no sense at all.

If the VHF installation is rotten, it should be improved. Period. Regardless of splitter/no splitter. This is totally independent of the AIS, and adding a splitter to it will not degrade the VHF performance any worse than it is.

If someone cannot reasonably install a VHF antenna and connectors, they will equally fail at an independent AIS installation. This will leave them with a poor VHF and a functionally non-working AIS - a worse situation than adding a splitter.

To recommend people avoid splitters because many boats have poorly installed systems boarders on presumptuous, if not offensive. Alternately should people also avoid buying a new VHF radio because many others have poorly installed antenna systems, and one can only assume they do too? This doesn't make any sense.

If all you "professionals" have is to hang your hat on "I assume everyone has a bad VHF antenna system" as your only argument against using a splitter, then you are doing a disservice to people reading these threads. That has been the ONLY argument presented so far - beyond the unjustified and unproven (in thought or experiment) argument of it compromises the safety of the VHF.

And you guys are still avoiding specifying the validity of your statement that the VHF safety is compromised by addition of a splitter. Go ahead, give me a failure mode that takes the VHF out of operation. Please make this example realistic, and not something like "a lightning strike that hits the antenna and travels down the coax, but somehow avoids damaging it or blowing the VHF while surgically finding and opening the specific transistor that keeps the splitter failed over to the VHF".

I could use a good laugh!

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Old 13-12-2015, 05:32   #18
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Re: Which AIS antenna splitter

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Originally Posted by Hoghead View Post
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?
Not sure you really need one at the mast head -- we put our ais antenna on the top of our bimini between the solar panels and get great reception - I mean how far out do you want to see other boats or have them see you - We get boats as far as 50-60nm away but why -- we really want to see them 10-15nm out so we can watch and plan and watch
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Old 13-12-2015, 05:50   #19
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Which AIS antenna splitter

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Originally Posted by Hoghead View Post
Now which antenna?

Which cable as it seems that all are not created equal?
Vesper make an antenna specifically for AIS. It is the best choice IMO.

If you get a "good" splitter you don't need another "good" long cable. You just need one or two short cables from the splitter to AIS and VHF.

There is a lot of "religion" surrounding cables these days. LMR 400 is the best and RG-213 is probably a close second. Here is a page with performance of various cable types: http://www.universal-radio.com/catal.../coaxperf.html

You will be operating at 170MHz for AIS.
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Old 13-12-2015, 06:23   #20
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Re: Which AIS antenna splitter

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Originally Posted by chuckr View Post
Not sure you really need one at the mast head -- we put our ais antenna on the top of our bimini between the solar panels and get great reception - I mean how far out do you want to see other boats or have them see you - We get boats as far as 50-60nm away but why -- we really want to see them 10-15nm out so we can watch and plan and watch
It is never the Class A ship systems that one worries about. It is the poorly installed rail-mounted Class B ships that pop up 1-2nm away (or worse in bad seas) that one wants as much warning/projection as possible.

Since these only transmit every 30sec, it can be a LONG time between a good reception fix from a low antenna in a bad sea. We have watched these targets appear briefly, then disappear for a long time (long enough that the plotter dropped the target), before reappearing again.

On opposite tacks, it is conceivable that two boats may NEVER see each other until extremely close.

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Old 13-12-2015, 07:54   #21
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Re: Which AIS antenna splitter

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Originally Posted by colemj View Post
It is never the Class A ship systems that one worries about. It is the poorly installed rail-mounted Class B ships that pop up 1-2nm away (or worse in bad seas) that one wants as much warning/projection as possible.

Since these only transmit every 30sec, it can be a LONG time between a good reception fix from a low antenna in a bad sea. We have watched these targets appear briefly, then disappear for a long time (long enough that the plotter dropped the target), before reappearing again.

On opposite tacks, it is conceivable that two boats may NEVER see each other until extremely close.
Mark
Never had that problem in the 7 years we have been using AIS and sailing the Carib and the Med. The only time we have seen them drop and come back is when they are a bit away from us -- 8-10nm - not 1-2nm - even the ones who drop and come back get very strong at say 5nm which at 5-7k is a lot of time -

and that is why you keep watch anyway isn't it??????
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Old 13-12-2015, 08:38   #22
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Re: Which AIS antenna splitter

My experience with a dedicated rail-mounted AIS antenna that is tuned to AIS frequencies (i.e. antenna is purpose built).

Reports back to me are that I'm seen 5-8nm away with no drop outs (could be further, never asked anyone further away). I see Class A way further than necessary and Class B always at least 4nm. I find Class B at 4nm more than adequate time to make necessary course changes, in fact normally monitor them until ~2nm away. BTW, 4nm is further than you can see 40 something foot boats on radar.

True Story: Anchored next a buddy boat (who has a taller mast than me), I was carrying on a conversation with a 3rd party on VHF that was 20+ miles away. The buddy boat could not hear the 3rd party's transmission, I heard them just fine. I queried about squelch, and was told he adjusted it and still couldn't hear the far end. The buddy boat has an antenna splitter (of unknown to me brand/model). (Yep! I'm blaming the splitter!)
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Old 13-12-2015, 09:58   #23
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Re: Which AIS antenna splitter

SailRedemption,
I'm NOT saying that "splitters" are bad, nor that you will die if you use one, etc...and, since I use the SP-160, that should be obvious!! (but it seems that others here are more interested in arguing, than in accepting that we can all have different opinions, based on your specific applications / desires / preparations, etc...)
Vesper AIS SP-160 "relay/splitter" test results, lab/real world

What I am saying is that anyone that just blanketly writes that there are no issues in using a "splitter/relay" for and AIS transponder and VHF radio, on one antenna, is not practicing "good engineering" nor good seamanship, and is doing a disservice to all of their fellow sailors....

Those that disagree with me here, no worries....I'm a big boy, and I know that we all are entitled to our opinions...and I will not argue the point....
Please give me the same respect!

And, please read what I wrote in bold type, right up front:
Quote:
Originally Posted by ka4wja View Post
--- in general I agree with Bill here....for most cruisers, his advice/recommendations are good...
SailRedemption, since you pose an honest question, and from your words and choice of cable/connectors I'm assuming you've got no additional losses from kinks/bends/connector installation issues/moisture/etc...
And, that you have thought through the scenarios that could cause a "splitter failure", such as a close lightning strike, and how you'd deal with that!!??

{for me, and my boat / my application, I have taken care of the above (I used LMR-240uf in the mast, and LMR-400uf in the bilge/cabin, with clean, well done connections....and have splitter bypass jumper cable right there, at the ready....and have a new stern-mounted VHF antenna already mounted/wired/tested, ready to be connected to either the primary VHF, or AIS transponder, or a backup VHF), but since I'm not on your boat, or others' boats, I try to use "good engineering" and "good seamanship", when answering questions here, not just writing "yep, I do it...so go for it"...}


So, since your question was specific to coax losses, I will just deal with that here....although everyone should remember what I wrote above: If everything else isn't perfect, what you calculate will not match the real world!


FYI, Belden 9913F7 is a good low-loss replacement for RG-213/U RG-8/U (and especially of the original spiral-dielectric 9913 coax......F7 has closed-cell foam dielectric eliminates the water displacement and center-conductor migration problems which plagued the original 9913!) It's similar to Times Microwave Systems LMR-400UF but with a PVC outer jacket. Using it should represent a significant reduction in loss, versus the typical RG-8x!!
BUT...
But, please read this thread, for an understanding of why we have the ranges that we have, the margins that we have, and "how" all of this "radio stuff" works...I think it will open the eyes of anyone who is actually "open"
VHF and AIS Radiowave Propagation and VHF and AIS Radio Range


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-8x

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...

{With the original design of the VHF maritime comms system (from before I was born), allowing 3db of cable loss....and from the fact that almost all of our VHF comms is line-of-sight (where we have significant margins of dozens of db's)....all of the quibbling over 1db to 1.5db of extra loss / of less loss, does start to show how we can take things to the extremes....BUT...

But, lest we forget that in times of emergency / distress, we want as little loss in the system as possible!
And, "good engineering" / "good seamanship" demands that we actually take these rather numbers seriously!!
So, do you wish to take the chance that this added loss will contribute to loss of your life, or that of a loved one??
That is a question you must answer, not me...

And, what are ready to do if your splitter/relay fails???
Do, you have a new coax jumper to bypass it?
Does it have clean connectors?
Do you have a PL-258 barrel, or two?
Do you have a VHF power/swr meter (not one that is designed for HF, but rather one that actually works on VHF)?
Can you instantly recognize / notice if you have had a "splitter/relay" failure?}


So, you see, there is a LOT to all of this....which is why I wrote what I wrote....
I generally agree with Bill...

Since, if we can't get most posters here to read a few paragraphs of information, or watch a few minutes of video, etc...and a large percentage of cruising sailboats have a rather poor VHF system on-board!!
Sorry if this ruffles feathers of some, but have a look and you'll find the over-whelming majority have ~ 100' of RG-8x, and many have RG-58....and many have old/corroded connectors...and many have old-non-DSC radios...many have frayed mic cords, crackling speakers, mics that do not allow full deviation, etc. etc. etc. etc....I hear and see this all the time!!!!)
With all of these things, how in the world do others here think we can get someone to actually spend the time and money to improve things, when all the advertising / marketing / boat show hucksters / etc. simply say "buy this...and you'll be 'safer' "!!!
And, this is why I "generally agree" with Bill!!


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...

But, that does NOT mean that I disagree with Bill, as the original poster (and most others) have most probably not taken the care required to actually make an informed decision (and unfortunately most sailors view "radios" as some mysterious system that is part "magic" and part WWII-era anachronistic / quaint....and never bother to learn anything about them...assuming that all you do is buy what is advertised and all is well...)


I told 'ya there was a LOT to all of this...

And, everyone please understand that I'm NOT trying to "have it both ways"....rather, I'm trying emphasize that there is a LOT to all of this!!
And, with both my earlier caveats and the further details I write here, I do hope that you all grasp what I'm saying???
In my opinion and in my experience, all "splitters" are not "bad" per se....but, recommending them blanketly is bad, very bad!!
And, here again, this is why I "generally agree" with Bill....

I do hope this clear things up....yes??

If not, I'm sorry....but, I'm not sure how to be anymore clear....(please read the links I provided, too!)



fair winds..

John
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Old 13-12-2015, 14:15   #24
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Re: Which AIS antenna splitter

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Originally Posted by btrayfors View Post
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
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There's the question of AIS receiver or transceiver. A receiver can be quite sensitive at a distance even in the most basic sense. I had an emergency Signal Mate whip/PL259 antenna inside my steel pilothouse before I had the mast up, and my SH 2200 could receive AIS info from targets 10 NM off. Of course, into a Metz whip 45 feet up, it's even better.

If you want to trasmit, however, height is better to be seen on the open ocean from a distance, and being an AIS target for wood or fibreglass sailboats is often easier than being a RADAR target in rough situations.

A splitter is a compromise, save for the products listed above, which combine a signal booster aspect. If you have little room at the mast head, you could have an AIS antenna on a spreader, too.
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Old 13-12-2015, 14:23   #25
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Re: Which AIS antenna splitter

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Originally Posted by btrayfors View Post
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
Especially if you can turn off the TX! Really, even with "limited" AIS receive only, I have been very impressed with it and with the advent of virtual buoyage and "AIS targets", the situation looks only to improve for most of it. I feel AIS and RADAR to be very complementary technologies, particularly as the monitoring of VHF frequencies in commercial shipping seems not to have been as attentive as it once was. If I can see 22 knot freighters over the horizon because they are transmitting a string visible from their mast top to mine...I have far more minutes available to me (even if they have yet to notice me) than is often the case with RADAR.
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Old 13-12-2015, 14:58   #26
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Re: Which AIS antenna splitter

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Originally Posted by ka4wja View Post
Those that disagree with me here, no worries....I'm a big boy, and I know that we all are entitled to our opinions...and I will not argue the point....
Please give me the same respect!

This disappoints me John. Debate on these points is good for the community and demanding that someone not argue with you when you make debatable points is unlike what I have come to expect from you.

But, lest we forget that in times of emergency / distress, we want as little loss in the system as possible!
And, "good engineering" / "good seamanship" demands that we actually take these rather numbers seriously!!
So, do you wish to take the chance that this added loss will contribute to loss of your life, or that of a loved one??
That is a question you must answer, not me…

This is an appeal to emotion and a logical fallacy to boot. One can always "what if" things and argue minutely decreasing risk until one cannot even leave the dock.

And, what are ready to do if your splitter/relay fails???
Do, you have a new coax jumper to bypass it?
Does it have clean connectors?
Do you have a PL-258 barrel, or two?
Do you have a VHF power/swr meter (not one that is designed for HF, but rather one that actually works on VHF)?
Can you instantly recognize / notice if you have had a "splitter/relay" failure?}
Again, please give me one reasonable failure mode a good splitter can have which leaves the VHF inoperable. To keep bringing up splitter failure as a danger to VHF safety without explaining how this can happen is unprofessional and disingenuous.

I am in disbelief that you actually brought up the very argument I said was outlandish - that a lightning strike can surgically hit the antenna and leave everything connected to it intact and operable EXCEPT opening up the single transistor that is normally shunted closed to the VHF.

The odds of that happening are similar to the odds of quantum uncertainties causing all your body's particles to tunnel 50' to the left and leave you instantly transported from where you are sitting.

We have had a lightning strike. The entire face of the VHF blew across the room and the antenna was vaporized. Interestingly, it is quite possible that if a splitter was installed then, that our VHF would not have been damaged and be usable with a spare antenna - which would imply that a splitter INCREASES VHF safety in the event of lightning.

Just so everyone is clear on this point - a good splitter has ALL failure modes, as well as its powered off mode, defaulting to the VHF operation.

But if you are really worried about that, then just tape a barrel connector on the splitter. Unscrew the "VHF in" and "antenna out" connectors and connect them with the barrel connector. This will cost you another $3.

Mark
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Old 13-12-2015, 16:09   #27
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Re: Which AIS antenna splitter

Hoghead,
Not knowing your boat, nor how you'll install/mount the antenna, nor even where you are located / where and how you will be sailing/cruising, it's difficult to give you an absolute / definitive answer....
But, in general....
Quote:
Originally Posted by Hoghead View Post
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.
Yes, this is good.

Installation is not much more difficult, and a backup second antenna if ever needed.
Yes, this is good as well...

Now which antenna?
One that doesn't shade your solar panels (if you have solar on your arch?)....
And, one that has an SO-239 connector, so that you can use your own coax...not one that has coax pre-attached...

I prefer Shakespeare 3' "1/2-wave" SS whips....but, if you do not have solar panels, their 4' fiberglass radome covered, end-fed 1/2-wave antennas are also very good, and won't "whip around" as much in heavy winds/seas...

See below for details on antennas..

Which cable as it seems that all are not created equal?
Again, not knowing your boat, nor how you'll installing/mounting your antenna, I cannot be absolute here...
But, in general, you're not likely to need more than 35' of coax....and possibly even less, as you originally wrote that you were adding "a new black box AIS", and understand that you may be able to mount the "black box" closer to the antenna than the Nav Station is, and run the NMEA cabling a few feet from the "black box" to the Nav Station...

See below for LOTS of details on coax...

As for antennas....
Try Shakespeare 5215 or 5242-A....

Shakespeare Classic 5242-A VHF Antenna

Shakespeare 5215 Squatty Body VHF Antenna





As for coax...since your arch-mounted antenna will not need a long run of cable, the loss in the exact cable you use will not really effect things much....but, for simplicity, longevity, etc.....try RG-213....no hassles, no worries....
(but, if you wish to snake the coax thru your arch, you may want to use a smaller coax, such as a good quality RG-8x....)

The loss differences:
33' of RG-213 = 0.9db
33' of RG-8x = 1.5db
And, you'll never notice the 6/10 of db difference!!!



If you wish some more details...have a look here..
Good coax both for low VHF loss and corrosion

Antenna recommendation

AIS Antenna on Spreaders




I hope this helps...

Fair winds...

John
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Old 13-12-2015, 16:29   #28
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Re: Which AIS antenna splitter

I can only laugh to myself when you see the words Zero Loss on a splitter
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Old 13-12-2015, 16:42   #29
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Re: Which AIS antenna splitter

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I can only laugh to myself when you see the words Zero Loss on a splitter
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?

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Old 13-12-2015, 17:43   #30
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Re: Which AIS antenna splitter

ka4wja

SailRedemption, since you pose an honest question, and from your words and choice of cable/connectors I'm assuming you've got no additional losses from kinks/bends/connector installation issues/moisture/etc...
And, that you have thought through the scenarios that could cause a "splitter failure", such as a close lightning strike, and how you'd deal with that!!??

I have enough cable that I can bypass the splitter and plug right into one of the two VHF radios. I have been struck by lightning and I'm a firm believer that nothing can be planned to curb it minus carrying a spare antennae. So I don't understand what having a splitter or no splitter would have to do with a lightening example. I do plan to have the second SH radio with an antennae on the stern.


But, lest we forget that in times of emergency / distress, we want as little loss in the system as possible!
And, "good engineering" / "good seamanship" demands that we actually take these rather numbers seriously!!
So, do you wish to take the chance that this added loss will contribute to loss of your life, or that of a loved one??
That is a question you must answer, not me...

I don't understand this question.. I don't get how a 1.5db loss is going to "contribute" to loss of life. Are you suggesting that if I use a splitter I'm in someway jeopardizing the lives of my crew and myself? That's silly.


And, what are ready to do if your splitter/relay fails??? Plug the main antennae wire straight to the radio
Do, you have a new coax jumper to bypass it? See above
Does it have clean connectors? I don't see why they would be otherwise.
Do you have a PL-258 barrel, or two? As cheap as they are, I don't see why not.
Do you have a VHF power/swr meter (not one that is designed for HF, but rather one that actually works on VHF)? This I don't have, but is it necessary? I have never used one so I'm ignorant here..
Can you instantly recognize / notice if you have had a "splitter/relay" failure? With two radios you can see if they are working or not, but not signal strength though, I take the swr meter could?



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. (:


I do hope this clear things up....yes??

It does, thanks.. I should be fine with the SP-160 for VHF/AIS for the masthead with no issues.
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