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Old 17-03-2013, 16:45   #16
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Re: VHF transmitter location

As an EE, I concur with the previous post! Mauritz
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Old 17-03-2013, 16:48   #17
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Originally Posted by S/V Illusion View Post
The failure rate of splitters may be debatable but the inherent insertion loss created by using one isn't. Considering both the potential for failure and the loss, splitters are a bad compromise.
Insertion losses have no real practical effect on VHF. I've never seen any real life difference across several brands and installation using splitters. Height trumps power.

Dave
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Old 17-03-2013, 16:49   #18
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Re: VHF transmitter location

Quote:
Originally Posted by S/V Illusion View Post
The failure rate of splitters may be debatable but the inherent insertion loss created by using one isn't. Considering both the potential for failure and the loss, splitters are a bad compromise.
Quote:
Originally Posted by Teknav View Post
As an EE, I concur with the previous post! Mauritz
Exactly right!

And, if you think that it's an easy matter to reconnect your VHF to the masthead antenna (which is connected to, e.g., the AIS splitter), then you haven't seen very many AIS installs.

In several of my clients' boats, it is a nightmare merely to reach the AIS boxes, tucked deep in lockers, behind "removable" panels, etc. It ain't always easy.

And, try it in a seaway when you have an emergency!

And, of course, if you should experience an AIS/splitter or other splitter failure, it could damage your VHF transceiver by presenting a dead short or an open circuit to the VHF transmitter.

SPLITTERS ARE NOT A GOOD IDEA on a boat's primary VHF system!

Bill
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Old 17-03-2013, 16:58   #19
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Re: VHF transmitter location

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Originally Posted by goboatingnow View Post
Insertion losses have no real practical effect on VHF. I've never seen any real life difference across several brands and installation using splitters. Height trumps power.

Dave
Actually, a typical insertion loss of 1 to 2dB can effectively reduce radiated power by 30 percent and more due to the additional connectors required, each of which adds to the net loss. If you add the potential for moisture intrusion in these connections, the loss is exacerbated. It's quite conceivable one might never notice the degradation especially as it typically occurs gradually.
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Old 17-03-2013, 17:01   #20
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Re: VHF transmitter location

Quote:
Originally Posted by goboatingnow View Post
Insertion losses have no real practical effect on VHF. I've never seen any real life difference across several brands and installation using splitters. Height trumps power.

Dave

Typical splitter loss is 3.5 to 4.0db. That's a 50% loss in power, both transmitting and receiving.

With a typical splitter you are losing 50% of your power....equivalent to having a 12.5watt VHF transmitter instead of a 25watt transmitter.

Do you really think that makes "no real practical effect on VHF"?? Especially with FM modulation and the "capture effect"????

We're not talking about height here. Of course height is important, but that has little to do with splitters. And, for a cockpit-VHF with a sternrail mounted VHF antenna, height really doesn't matter; what you're mostly interested in are boats nearby and ships within line of sight....say, a radius of 5-6 miles.

If you're really concerned about maximum distance potential from a cockpit VHF, then get a main VHF with a remote microphone.

Bill
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Old 17-03-2013, 17:01   #21
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Originally Posted by btrayfors View Post

Exactly right!

And, if you think that it's an easy matter to reconnect your VHF to the masthead antenna (which is connected to, e.g., the AIS splitter), then you haven't seen very many AIS installs.

In several of my clients' boats, it is a nightmare merely to reach the AIS boxes, tucked deep in lockers, behind "removable" panels, etc. It ain't always easy.

And, try it in a seaway when you have an emergency!

And, of course, if you should experience an AIS/splitter or other splitter failure, it could damage your VHF transceiver by presenting a dead short or an open circuit to the VHF transmitter.

SPLITTERS ARE NOT A GOOD IDEA on a boat's primary VHF system!

Bill
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Firstly all modern VHFs will handle dead shorts or opens. , try it and see. ( and both are not uncommon in poor VHF setups either)

As to installs , well that's down to the install. On mine its was a simple matter of unscrewing and reconnecting a couple of plugs. Most AIS units I've seen are installed behind the electrical panel at the chart table. Easy enough to get at.

Its all very well debating pros and cons , but lets try and not just promulgate hearsay or scaremongering , there are some small technical disadvantages and there have been occasional failures from cheap no-brand gear. But the fact is all the major companies are confident enough to build them into their AIS.

Anyway for most practical purposes a handheld VHF is sufficient for 90% of needs ( in fact virtually 100%)

As with all instals good proper installation in an accessible area is just good practice and that has nothing to do with splitters.

Dave
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Old 17-03-2013, 17:14   #22
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Quote:
Originally Posted by btrayfors View Post

Typical splitter loss is 3.5 to 4.0db. That's a 50% loss in power, both transmitting and receiving.

With a typical splitter you are losing 50% of your power....equivalent to having a 12.5watt VHF transmitter instead of a 25watt transmitter.

Do you really think that makes "no real practical effect on VHF"?? Especially with FM modulation and the "capture effect"????

We're not talking about height here. Of course height is important, but that has little to do with splitters. And, for a cockpit-VHF with a sternrail mounted VHF antenna, height really doesn't matter; what you're mostly interested in are boats nearby and ships within line of sight....say, a radius of 5-6 miles.

Bill
Sorry dedicated AIS splitters with insertion losses under 1db are readily available. ( milltech, comar , Simrad etc)

In practice , I have sailed , on 6 boats that had splitters. I could make out no difference in VHF range and or clarity.


For class B AIS. Its very useful to transmit as far away as you can. Its not You seeing them , its THEM seeing you , that's the key. Many ships will change course , over the visible horizon to avoid " WAFIs " . I've seen it happen. I see no benefit in arbitrarily restricting the range of AIS , no more then I do for voice.

When I see feedback of statistically relevant splitter failures , it then becomes a valid argument against their use, right now, your whole VHF is likely to fail , as your splitter is.

Dave
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Old 17-03-2013, 17:39   #23
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Re: VHF transmitter location

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Originally Posted by goboatingnow View Post
Firstly all modern VHFs will handle dead shorts or opens. , try it and see. ( and both are not uncommon in poor VHF setups either) .................
Hmmmm. Let's see......

To quote just a few:

Icom M604 (high-end VHF)

Instruction manual, p9
_ Receiving and transmitting
"CAUTION: Transmitting without an antenna will damage the transceiver."

--------------------------------------------------------------------------------------------------------

Icom M504 (mid-range VHF)

Instruction manual, p8
"3 BASIC OPERATION
_ Receiving and transmitting
CAUTION: Transmitting without an antenna may damage the transceiver."



Furuno FM-3000 VHF

Instruction manual, p7

2.2 Receiving and Transmitting
Caution:
Transmitting without an antenna may damage the transceiver.


Yeah, most VHF's these days have protective circuits. But, why in the devil would you want to test them, and what makes you think they provide 100% protection against shorts and opens?


It's a bit like testing your collision-collapsible fenders and engine compartments on your car :-)


Bill

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Old 17-03-2013, 18:00   #24
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Re: VHF transmitter location

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Originally Posted by goboatingnow View Post
Sorry dedicated AIS splitters with insertion losses under 1db are readily available. ( milltech, comar , Simrad etc)
......
The AMEC dedicated splitter sold by Milltech Marine has a 4db insertion loss on receive paths for both VHF and AIS. It has a 4db insertion loss for transmit on AIS, and a claimed 1.5db insertion loss for VHF transmit.

The Comar dedicated splitter sold by Milltech Marine also has a 4db insertion loss on receive paths for both VHF and AIS. It has a claimed 0.8db insertion loss for transmit on both AIS and VHF.

The Simrad NSPL-400 splitter is not a splitter in the usual sense. Rather, it's a solid state relay, with fast switching. It claims a 0db insertion loss on both AIS and VHF receive, and a <1db insertion loss on transmit for both AIS and VHF. This is an interesting device. I'd love to see the circuitry.

Still, I believe my original statement to be essentially correct in that most splitters have what I consider to be both unacceptable insertion losses and the risk of function loss and/or damaging failure. These could place either the VHF or the AIS at risk or, worse, you and your boat in the event that failure occurred at just the wrong time. And, as we all know, Murphy lurks aboard every boat and plays havoc with incredible timing!

Bill
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Old 17-03-2013, 18:22   #25
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Re: VHF transmitter location

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Originally Posted by goboatingnow View Post
Firstly all modern VHFs will handle dead shorts or opens. , try it and see. ( and both are not uncommon in poor VHF setups either)



Its all very well debating pros and cons , but lets try and not just promulgate hearsay or scaremongering ,

Dave
When all you have offered thus far is anecdotal declarative statements saying you have never noticed any problem(s), shall we accept that as empirical evidence after everything else I and others have said?

I know this is this forum usually devoid of any support but do you have aNy evidence to back up what seems to be a subjective opinion?
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Old 17-03-2013, 18:22   #26
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Re: VHF transmitter location

...can we...ummm...can we all just get along?...sniff We all made our case...let's leave it at that! Mauritz
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Old 17-03-2013, 18:29   #27
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Re: VHF transmitter location

Digital Yacht offer the SPL 250 Splitter....but!



...i wouldn't use or recommend a splitter....
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Old 17-03-2013, 18:31   #28
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When all you have offered thus far is anecdotal declarative statements saying you have never noticed any problem(s), shall we accept that as empirical evidence after everything else I and others have said?

I know this is this forum usually devoid of any support but do you have aNy evidence to back up what seems to be a subjective opinion?
I'm innocent until proven guilty as are splitters.

Dave
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Old 17-03-2013, 18:36   #29
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The AMEC dedicated splitter sold by Milltech Marine has a 4db insertion loss on receive paths for both VHF and AIS. It has a 4db insertion loss for transmit on AIS, and a claimed 1.5db insertion loss for VHF transmit.

The Comar dedicated splitter sold by Milltech Marine also has a 4db insertion loss on receive paths for both VHF and AIS. It has a claimed 0.8db insertion loss for transmit on both AIS and VHF.

The Simrad NSPL-400 splitter is not a splitter in the usual sense. Rather, it's a solid state relay, with fast switching. It claims a 0db insertion loss on both AIS and VHF receive, and a <1db insertion loss on transmit for both AIS and VHF. This is an interesting device. I'd love to see the circuitry.

Still, I believe my original statement to be essentially correct in that most splitters have what I consider to be both unacceptable insertion losses and the risk of function loss and/or damaging failure. These could place either the VHF or the AIS at risk or, worse, you and your boat in the event that failure occurred at just the wrong time. And, as we all know, Murphy lurks aboard every boat and plays havoc with incredible timing!

Bill
http://www.milltechmarine.com/Smart-...ter_p_171.html

<1db

As are several others

http://www.milltechmarine.com/Vesper...ter_p_225.html

1db

http://www.milltechmarine.com/Comar-...ter_p_189.html

Receive path losses have little real effect.

Dave
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Old 17-03-2013, 18:38   #30
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Re: VHF transmitter location

Some of you guys must have an Irish streak...err...tamper! Relax and enjoy the steel band music playing...have some wine, crackers and cheese...and look at the stars so far away...ummm, never mind...don't look...don't want you to start another argument about celestial navigation and the use of sextants. Mauritz
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