AIS trouble. Radio?

[KayZee]

Heres the set up: Raymarine E80 network, ca. 2006. AIS via Standard Horizon vhf nmea'ed into network. Both MFD's and the remote have to be on to pass the signal down the chain or I get "No ais" at display.

Here's the problem: Low distance for targets. Even commercial transponders drop off at about 2.5 miles. Close in targets fade on and off the screen with the blue line of death. In our 5,000 boat recreational marina, sometimes we get 100's of targets; other times we get 12.

Things we've done: voltage and connections checked and serviced behind VHF. Checked condition and connections of the Ancor RG8x. Jacket is in great shape, connections look good no apparent corrosion at either end. Changed old and crusty looking Shakespeare VHF antenna for a shiny new Metz Manta 6.

What we haven't done, SWR check though I have a ham friend who can help me with this.

VHF seems to be working normally and all setting at radio and a.i.s. settings and VHF in MFD have been checked repeatedly. Could this just be a bad set-up? Is a.i.s from the VHF just a poor idea? Could it be that the splitter/receiver in the VHF is cr@p? Standard Horizon does not recommend using a seperate antenna.


What we want: situational awareness of boomers that ply the alongshore shipping channel in our area. Two point somethng miles is too close for comfort.

TIA Kurt

[Tsuru]

On our older boat we connected the Standard Horizon VHF/AIS to the Raymarine MFD via the older NEMA 0183 network, even theough we had the Raymarine NEMA 2000 SeaTalkng network. Don't recall why I went that way but it worked very well. We used an antenna splitter if memory serves. Good luck.

[wholybee]

Enlist help from your HAM friend. 99% something is wrong with either the coax, connectors, or antenna.

RG8x is terrible coax. It is fine for short runs, but usually on a sailboat I recommend against it, since even with a small sailboat the run is fairly long to the top of the mast. Depending on length, you might be loosing 50%-75% of your signal.

Your HAM friend hopefully knows this, but with a lossy cable like RG8x, you can read a good VSWR on the meter, and still have serious problems. Hidden by the cable losses. So, just because the VSWR tests good, does not mean it is good. (but bad VSWR always means something is wrong)

It might be worth cutting off a connector, and seeing if there is any corrosion of the wire itself. If there is any sign of corrosion or water inside the coax, the whole run needs replaced. If you are not experienced putting on a new connector, know that it is very easy to mess up, and have it look fine, and work fine for 6 months before it stops working.

1%, Something is wrong (damaged) with the VHF radio. I can't think of any settings that would do this, but perhaps the internal switch or splitter burned up. It does happen that a radio fails, but reception issues are almost always an issue with the coax or antenna.

Sharing an antenna with both the VHF and AIS signals is fine. With a VHF that has a built in AIS receiver, I don't think it can be done any other way.

[Tin Tin]

I would not rely on AIS for situational awareness, it is a useful tool to support your eyeball navigation and nice overlaid on a radar plot. By Boomer do you mean submarine? US navy does not always transmit on AIS and neither do the fishing boats.

[fxykty]

Since you’re sharing the antenna and cable with your VHF, what are your VHF receive and transmit ranges? If those are good, then probably not cable/antenna. But if not so good, then as wholybee points out it is likely your cable.