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post #11 of 17 Old 05-11-2014 Thread Starter
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Re: AIS / Marine Traffic

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Originally Posted by SVAuspicious View Post
If you like we can schedule a time to meet up and I'll put an antenna analyzer on your system for you.
Thank you. I may take you up on that at some point.

FWIW...

I was being picked up sporadically on MarineTraffic and aprs.fi this weekend. Both sites listed K3ARS as the source. K3ARS is in Chestertown, MD which is 24 NM from my slip. As far as I can tell this is the closest base station to Annapolis. It's no wonder that I don't show up consistently. At that range I'm surprised I show up at all.

I did ask a few boats if they could see me on their AIS. All said they could, so I guess it's working as it should. One said my data was not populated in the system, but I think that was due to my single antenna / splitter setup. They called me back a few minutes later and said all the data was there now.

My VSWR was showing up in ProAIS2 as 1.1:1.

I may add a second antenna some day, but what I have is going to have to be good enough for a little while.
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post #12 of 17 Old 05-12-2014
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Re: AIS / Marine Traffic

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I did ask a few boats if they could see me on their AIS. All said they could, so I guess it's working as it should. One said my data was not populated in the system, but I think that was due to my single antenna / splitter setup. They called me back a few minutes later and said all the data was there now.
That should not have anything to do with the splitter unless you were spending a lot of time talking on your VHF after you powered up. Static data (IIRC) for Class B is only sent every six minutes, and if you're talking on the VHF the splitter will block the AIS transmission.

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post #13 of 17 Old 05-12-2014
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Re: AIS / Marine Traffic

I tried installing a class B ( Si Tex) and am having problems with the vhf ant also. It starts up fine, has good GPS signal, sends first location with mmsi # and then goes to fail mode(ais ant). I have a new dedicated ant on the pushpit and even hooked up a spare with a new cable. This is the second black box I have tried and both vhf ants work fine with voice comm. where to now?

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post #14 of 17 Old 05-12-2014
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Re: AIS / Marine Traffic

Talked to an engineer at Si-tex. Seems like you need an SWR on your antenna that is less than 5 to 1. Interference from metal near the antenna ( like on the pushpit)is a no no also. I hooked up to the mast head antenna and all is well. With a laptop plugged into the USB on the AIS you will get a readout on the current SWR after you get the fail light or after a few minutes if all is well. Seems like your vhf radio will T and R on a pretty lousy antenna.

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post #15 of 17 Old 05-13-2014
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Re: AIS / Marine Traffic

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Talked to an engineer at Si-tex. Seems like you need an SWR on your antenna that is less than 5 to 1. Interference from metal near the antenna ( like on the pushpit)is a no no also. I hooked up to the mast head antenna and all is well. With a laptop plugged into the USB on the AIS you will get a readout on the current SWR after you get the fail light or after a few minutes if all is well. Seems like your vhf radio will T and R on a pretty lousy antenna.
There is no excuse for an VSWR as high as 5:1.

I'm not sure what "interference from metal near the antenna" means. There can be shielding and directive effects, but not interference. The near-field effects of metal near the antenna at the mast head and on the pushpit is not significant, absent "junk on the back."

Just because the equipment functions doesn't mean it is performing as you expect.

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post #16 of 17 Old 05-13-2014
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Re: AIS / Marine Traffic

Thanks Dave. Do you suppose the software in the AIS is just coming up with wildly high SWR. I am not very electronic smart but I have never had so much trouble with plug and play.

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post #17 of 17 Old 05-15-2014
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Re: AIS / Marine Traffic

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Do you suppose the software in the AIS is just coming up with wildly high SWR.
Very unlikely. If it was a software problem there would be more widespread reports of similar issues.

It shouldn't be hard to get VSWR well below 2:1. Any local ham (check ARRL.org for clubs in your area) with a VHF SWR meter can help you. An antenna analyzer is better ...

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