AIS Fault Message

[Paul Elliott]

Originally Posted by Emerald Sea

Paul. The brand of the antenna eludes me and Id have to go up the mast to check. Unfortunately my receipt doesn't include the name. Its a 2.4m fiberglass 6dB VHF antenna, similar to the Shakespeare Mariner type. I did check all the connections and did a continuity check at the base connection which showed 0.2 which, when I called Radio Holland about this, said it was acceptable.

This sounds like the higher-gain style of antenna I was mentioning. I've only done the measurements on a few of these, but at least on mine the antenna tuning is much sharper than it is for the short VHF whips. I measure a good SWR on channel 16, and a pretty bad one (the number escapes me) on the AIS channels.

If you had a it was a shield whisker that was hitting the center conductor at the plug this would have surely shown up on a continuity check, no?

The antenna itself looks like a dead short, and the coax ran into the antenna without a connector (the antenna was a long fiberglass whip, like yours). With my ohmmeter I couldn't really tell if the short was at the connector, or at the antenna.

There is a neat bit of gear called a "reflectometer", that can pinpoint the location of a short or open, but I didn't have one with me.

Not sure if this part of the puzzle, but the previous RG58 coax had a short, 1m long, RG58 pup piece between the main coax and the AIS 100 splitter. I removed this and plugged the new RG233 direct into the splitter (PL259). I didnt understand this need for this pup length so just left it out. I havent tried to replace it, simply as the coax fittings (cable to cable, not a PL259) weren't in my stock.

Are you sure this jumper cable isn't supposed to go between the AIS splitter and the VHF radio? I suppose not, since you say your VHF is working...

[MikeFergie]

Have you plugged a usb cable into the AIs unit directly to a pc and installed the raymarine software ?

This allows you to run through checks and it specifically identifies errors on the pic software interphase


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[gbgreen59]

I got the same error message for the same AIS unit. The RF cable and antenna were probably original to the 30 year old boat, so I replaced both the cable and antenna. The error message went away.

[ka4wja]

Steve, et al,
By the time I read this thread and found out it was about a VSWR issue, Steve is already at sea / on-passage...so, he's got what he's got...(I don't have enough time to read everything here! I wish it had "VSWR fault" or some such wording in the title...)

Originally Posted by Emerald Sea

PS, we leave Namibia for St Helena later today so it will be 10-12 days before I receive CF emails. This support is great! Beers on me ... Should we meet up.

But, at least I can offer a few tidbits of info that Steve, and all of you, will probably find helpful!

1) None of us being there with Steve, on Emerald Sea, further since we do not know what the "SWR" actually is, nor what it was, nor what coax was there, nor what is there now, we cannot be certain of anything.....so, we just do our best to offer the advice that seems to make the most sense!!

So, just a tip for anyone else....take the time to give everyone here the most detailed description of the issues you can, with as much info/specifications as possible....
And, you're likely to get some great advice/assistance!!



2) As "continuouswave" and Paul have already explained in detail, a lossy transmission line (old, lossy coax) can mask an antenna's high SWR....
But, be aware that even if replacing the coax with the same type/size, you can see a marked decrease in loss, due to the old coax being old and more-lossy (if that a real word?), as well as because of new connections being better than the old ones!
So, a high SWR problem can be noticed when replacing the coax, even if not replacing it with a low-loss variety...




3) But, big kudos to Paul for picking up on what I was going to write!
Higher-gain antennas, especially higher-gain collinear verticals, will exhibit a narrower operational bandwidth (both in gain and VSWR)....

Originally Posted by Paul Elliott

This sounds like the higher-gain style of antenna I was mentioning. I've only done the measurements on a few of these, but at least on mine the antenna tuning is much sharper than it is for the short VHF whips. I measure a good SWR on channel 16, and a pretty bad one (the number escapes me) on the AIS channels.

Paul hit the nail on the head here!!!
Combine the high-VSWR at 162mhz of the typical "6db" [sic] marine VHF antenna, with the lower loss of new coax (and/or lower-loss coax), and you have a damn good guess of what's going on with Steve's set-up!!!


While a shorter VHF Marine Whip antenna (such as the typical 3' SS end-fed half-wave), should be able to have an acceptable VSWR across the entire 6mhz wide "VHF Marine Band", even some of these do not....and certainly most of the longer, higher-gain 8' / 6db[sic] do not....and the problem is worse for the larger antennas...
{note that some "new" versions may use a stagger-tuning, to allow a good VSWR near 156.8mhz and 162mhz (with a slight sacrifice in gain)....but most do not..}

FYI, here is an VSWR plot of my own Shakespeare 3' SS whip, mounted at the masthead (fed with 70' of LMR-240uf and 25' of LMR-400uf)....




I also have another Shakespeare 3' SS Whip (designed/factory-tuned for the AIS freqs, at the top of the VHF Band) on a pole, at the stern...but cannot find the VSWR plot! ARGG!!!
But, take my word for it, it has a VSWR of about 1.5:1 at 162mhz....



I hope this info helps some, and most find it at least, interesting?

Fair winds..

John

[Paul Elliott]

John, great point about the (likely) extra loss of the old coax. I wasn't considering that, and this could easily be the reason the OP is now seeing the alarm.

I have some return-loss plots of the short whip vs the long collinear whip, but won't be able to get at them for another ten days or so. The collinear was so sharply-tuned that the SWR exceeded 2:1 at the edges of the normal voice channels. On the AIS channels it was even worse. And that was using the permanently-attached RG58-style coax cable. (SWR numbers taken from my vague memory.)

[Emerald Sea]

We have arrived in St Helena yesterday and found internet (only available in local restaurants, no 3G). We endured the annoying alarm going off every 5-10min however once out of traffic lanes I just put the AIS on silent mode - my wife and I always maintain a 24hr watch. Ive read thru the replies and appreciate the feedback. A few plausible reasons here (thanks Paul, John).

I was reading thru the Raymarine VHF and AIS manuals and it makes a recommendation to use a low loss RG213 or equivalent cable for longer runs to avoid excessive losses in power output. As Ive used a RG223 Im assuming this should qualify (no?). Ive yet to try access the unit via the USB to PC.

Im now in the process of contacting Raymarine for a solution and will feedback here the findings.

Steve

[Emerald Sea]

A few months later and we still have not resolved this, still the same "External AIS Unit Fault, Antenna VSWR Fault" going off when the AIS is off Silent Mode. What we have in the last few weeks:

- AIS650 has been sent to Raymarine and returned with no issues.
- Updated all Raymarine with latest software.
- Have replaced the 6db mast mounted antenna with a Shakespeare 5215 AIS-VHF 3db 36" s/s whip.
- Check all coax connections between the Raymarine 100 Splitter and AIS 650 units including RG213 antenna coax (continuity 0.1 Ohms).
- Note that antenna coax, between splitter and mast top antenna, was replaced with a RG213 earlier this year.

Im still hunting a SWR meter and some knowhow as to how to use and read it.

Has anyone come across this error message before and found a solution?

[DeepFrz]

Just a thought but have you tried removing the splitter from the circuit and just let the AIS run and see what happens. This would of course disable your radio for the duration of the test so a hand held turned on would be a good idea.

[Paul L]

Have you tried running the proAis software on a PC for this unit with a USB cable? It will display what the unit thinks it sees along with the error messages.

[Emerald Sea]

Further to the above I can provide some more information. I plugged in the ProAIS2 software and also separated a few cables to isolate the systems.
There are two screenshots for each isolation.
Note: Mast antenna is a (newly installed) Shakespeare 5215AIS-VHF 3db 36" s/s whip; coax between mast head mounted antenna and AIS/Splitter: RG213 x 24m (installed Jan 2016), continuity checks OK.

Screenshot 1
This is the original setup with the mast antenna plugged into the Splitter100. Jumper coax between AIS650 and Splitter100.
Status: remains Red (error); will change to Blue when 'Silent' checked
VSWR Ratio: 8.8:1
I receive and send good AIS target info. VHF also good.

ProAIS2 - 1.pdf

Screenshot ProAIS-2
Mast antenna (RG213) plugged direct into the AIS650. Splitter100 not used (isolated).
Status: remains Red (error); will change to Blue when 'Silent' checked
VSWR Ratio:7498.4:1
I receive and send good AIS target info.

ProAIS2 - 2.pdf

There is a large difference in the (ProAIS) VSWR ratios between the two above. What would this indicate to you?


I was able to access a SWR tester (Daiwa 1.8 - 150MHz SWR & Power Meter) and we tested it only on the VHF radio with good results, however it didn't register any ratios for when the meter's cables were installed via the Splitter100 or AIS650. We were unsure this meter has the correct sensitivity for the AIS (?).

[Paul L]

Can you try test #2 with a longer coax a d the antenna mounted in a normal position?

Also, your displays showed the best after 8 transmits. You'll get more accurate results if you leave it to run longer so it can average out.

[DeepFrz]

I hope someone with experience on the ProAIS2 shows up to interpret the VSWR figures but I would try the AIS system with a different antenna. Preferably one mounted on the back rail with a coax patch cord to the transceiver. 8:1 VSWR is bad but I can't even guess what the other reading is saying. Open?

[Emerald Sea]

Paul, DeepFrz, quite right, I redid the 2nd test (coax, antenna direct into the AIS650; isolating the Splitter) and let it sit for a longer period and received an improved VSWR readings from ProAIS between 14.3:1 to 16.8:1 (see attached). However the readings don't tell me much as Im not a electech. Note also that with the coax/antenna directly connected I still get the VSWR alarm sounding off.

ProAIS2 - 2B.pdf

Paul, I don't quite understand what you are asking "Can you try test #2 with a longer coax and the antenna mounted in a normal position?". My coax is approx 22m long, runs up the mast and plugged into the 3db antenna. This is a 'normal' position - at least to me.

So far, by switching the antenna between the AIS650 and Splitter100 and having no desired improvement, it seems the fault would lie with the 22m coax or the new antenna. Since I just changed the antenna last week from a 6db to a 3db, with no change, then the coax seems to be the final area of fault. I did change this out earlier this year from a RG58 to RG213 and did continuity checks.

If I do change out the coax again, should I go back to a RG58?

[jeremiason]

Have you tried the Raymarine AIS Forum?

Might post there and should get an answer quickly!

Raymarine forum - AIS

[Neptune's Gear]

IMO the coax quality is insufficient for the low power output of a class B AIS, at the lead length you have (22m) .This is what your tests have shown you. Try a shorter run of coax to a temp antenna- even on the rail is good for a test. Every join and or connection will add to the losses, I prefer not to use a splitter.
If it still gives swr issues with the temp antenna, and a few m of new coax, with good clean connections, then the AIS is faulty, regardless of what Raymarine say.
Good luck !


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