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Old 28-05-2023, 13:52   #1
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Vesper XB-8000 reduced range

I have installed a Vesper XB-8000 in my boat last year. This AIS has a good reputation, but something is puzzling me.
When the boat is moored in the marina, the XB8000 is not visible on Marinetraffic or Vessefinder. Iíve read Vesper's FAQ about using Marinetraffic for AIS check, so I know that these services rely on crowd sourcing and that there are lots of gabs in the coverage, but the strange thing is that all other AIS equipped boats in the marine are continuously visible.
Iíve checked antenna cables and connections and didnít find anything suspicious. VSWR is 2:1 measured by Vesper's WatchMate, so presumeably antenna and cables are OK.
The antenna is a shared VHF antenna and I use the Vesper antenna splitter.
Other boats can see my AIS but I haven't checked the transmission range.
To me it seems that the XB8000 has a somewhat reduced transmission power.
Has anybody experienced a similar problem with their Vesper AIS?
I know that Garmin has taken over Vesper, but my experience with Garming support keeps me from asking them for advice.
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Old 28-05-2023, 14:02   #2
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Re: Vesper XB-8000 reduced range

Quote:
Originally Posted by Rollohund View Post
I have installed a Vesper XB-8000 in my boat last year. This AIS has a good reputation, but something is puzzling me.
When the boat is moored in the marina, the XB8000 is not visible on Marinetraffic or Vessefinder. Iíve read Vesper's FAQ about using Marinetraffic for AIS check, so I know that these services rely on crowd sourcing and that there are lots of gabs in the coverage, but the strange thing is that all other AIS equipped boats in the marine are continuously visible.
Iíve checked antenna cables and connections and didnít find anything suspicious. VSWR is 2:1 measured by Vesper's WatchMate, so presumeably antenna and cables are OK.
The antenna is a shared VHF antenna and I use the Vesper antenna splitter.
Other boats can see my AIS but I haven't checked the transmission range.
To me it seems that the XB8000 has a somewhat reduced transmission power.
Has anybody experienced a similar problem with their Vesper AIS?
I know that Garmin has taken over Vesper, but my experience with Garming support keeps me from asking them for advice.
Donít assume cable and antenna are good. First thing to test is the antenna cable straight into the AIS, leaving out the splitter and jumper coax.
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Old 28-05-2023, 14:06   #3
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Re: Vesper XB-8000 reduced range

My XB-8000 has worked reliably with no observable range issues for over 3 years.



Just because you have low VSWR doesn't mean the antenna/cable is working properly, only that it is a good electrical match to the transceiver.



How is the range/sensitivity of the VHF radio that uses this same antenna? Do you have another radio on board that you could compare with? Or a handheld that you can do a walk--away test on shore?



Also how far away are you receiving AIS targets? Does the receive range seem impaired?
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Old 28-05-2023, 15:13   #4
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Re: Vesper XB-8000 reduced range

You really need someone ( a ham probably) with a good graphical antenna analyzer to best characterize your antenna cable. It can do far more than simply give an an SWR at one frequency, for example identifying discontinuities in coax and connections, and giving indications of moisture intrusion.
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Old 28-05-2023, 19:06   #5
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Re: Vesper XB-8000 reduced range

The VSWR indicator on the Vesper is nearly useless. If it says things are bad, they most certainly are. But things can be very bad, and it will still report as good.

An experienced engineer or HAM with good test equipment can tell you a lot, down to the inch of where the problem actually is with the line or antenna.

Beyond that, ignore Marine Traffic. Again, (nearly) useless. Have a friend sail away from you and make constant radio checks. Record both the distance and quality of the VHF, and of the AIS. Also be aware that while not moving, your AIS only transmits once every 6 minutes. And because it is not SOTDMA, it might "collide" and transmit at the same time as another AIS, and the transmission will be lost. Say that happens 2x in a row, it might be 18 minutes before someone else sees you. That is while stationary. While moving it transmits every 30 seconds (IIRC) so that is much less likely to be a problem.

Check that the lights on the splitter are working properly. I forget exactly how they change, but the "splitter" is really a switch, and you should see it switch back and forth when you transmit on VHF compared to AIS. If it never switches to AIS, it will present a perfect 50ohm load to the AIS and the AIS unit will think everything is great.

The problem is most often an issue with a connector. Most often they problem can be found by visibly checking the connector by opening it up. If it doesn't look brand new, all shiny, with no signs of water or corrosion, then it is a problem. Some problems can not be seen, and require test equipment to identify.
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