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Old 26-09-2017, 09:21   #1
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Vesper Splitter VSWR

Hello,

I have noticed that my XB-6000 AIS is not being received as well as others with a similar antenna configuration in almost the same location at the same time.

I am using a Vesper antenna splitter. When the XB-6000 is connected directly to the antenna it's reporting a VSWR of 1, when I connect via the splitter its 2.

Before I start swooping cables around, what VSWR figure should I expect when transmitting via a splitter?

Thanks,

Aedan
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Old 26-09-2017, 13:35   #2
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Re: Vesper Splitter VSWR

I have the Vesper Watchmate X850, connected to antenna via a Vesper splitter, and the reported VSWR has always been 1.
Maybe a problem with the coax cable between the AIS and the splitter.
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Old 26-09-2017, 14:48   #3
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Re: Vesper Splitter VSWR

A splitter should not change SWR. But one which has failed will. That the SWR is 1:1 with it out of the circuit indicates the cable and connectors aren't the problem.

Having helped numerous people solve antenna issues, the first thing I check is the splitter which is usually the problem as these things are notoriously problematic.
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Old 28-09-2017, 00:25   #4
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Re: Vesper Splitter VSWR

Ok, thank you all for your help. I'll pursue the broken splitter theory, but first I'll eliminate the cables by swapping out the one that connects the AIS to the splitter, since that's easier than taking the splitter out and sending it off.

Thanks again,

Aedan
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Old 28-09-2017, 04:44   #5
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Re: Vesper Splitter VSWR

Just want to be sure you are reading the VSWR right. When you say it is up to 2:1 with the splitter in place, it is almost into the "red zone" on the little meter in the software, right? If it is really 1.2:1 and not 2:1, that is not a problem.

An SWR of 2:1 by itself would not significantly reduce signal levels in and out of the transponder. That level represents only a 10% level of reflected power, and it would be hard or impossible to detect a practical reduction in performance at that level.

If what you are saying is correct though, I would certainly agree there is some kind of problem somewhere between splitter input and transponder input, and the 2:1 SWR is an indication of that problem, though itself not the actual cause of a noticeable reduction in performance.

Chip
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Old 29-09-2017, 10:45   #6
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Re: Vesper Splitter VSWR

Hi Chip,

Thanks for your very clear reply.

Quote:
Originally Posted by SoonerSailor View Post
Just want to be sure you are reading the VSWR right. When you say it is up to 2:1 with the splitter in place, it is almost into the "red zone" on the little meter in the software, right? If it is really 1.2:1 and not 2:1, that is not a problem.
I can't get at the vmAIS software at the moment as the boat is about 200km away but I'm pretty sure it's 2:1 not 2.1:1. It's about 5 or six dots from the left and I think it's about to start into the red zone.

Quote:
Originally Posted by SoonerSailor View Post
An SWR of 2:1 by itself would not significantly reduce signal levels in and out of the transponder. That level represents only a 10% level of reflected power, and it would be hard or impossible to detect a practical reduction in performance at that level.

If what you are saying is correct though, I would certainly agree there is some kind of problem somewhere between splitter input and transponder input, and the 2:1 SWR is an indication of that problem, though itself not the actual cause of a noticeable reduction in performance.
I guess looking in this area is a good place to start since something is not as expected. I'll try swapping the splitter-AIS cable with the splitter-VHF cable and see if that makes any difference, but it may be a week or two before I can get back down to the boat. It's out of the water for the winter now sadly.

Thanks again for your help,

Aedan
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