Cruisers Forum
 


Join CruisersForum Today

Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 27-09-2018, 14:32   #1
Registered User

Join Date: Jun 2014
Posts: 5
Intermittent AIS signal

We have a 10 year old Raymarine AIS 500. Other boaters have reported to us that we are visible on their chartplotter only intermittently, that is, it on for a minute, then off, over and over (not sure of exactly timing though). We have checked it out while docked and not seen this behavior. Somebody told us that this it normal, due to congestion on the radio band used by AIS. Does this sound normal to anyone here? We have checked all the antenna connections to the AIS and everything seems solid.
__________________

jmckay123 is offline   Reply With Quote
Old 27-09-2018, 14:53   #2
Registered User

Join Date: Jun 2013
Location: canada
Posts: 2,310
Re: Intermittent AIS signal

Possible bad antenna And the unit is shutting off for high vswr.

Also it could be losing gps signal. Then it won't transmit. It will still receive.

Or the unit is just failing.

If yiu are close to the other boats you should be seen. Generally if they cut boats it will be the furthest ones away. Some cut off at 100 targets. It's pretty normal to see 100-150 targets in my area. But the ones 30-40 miles away will get cut if the screen has a limit.



You need the computer software to plug into pc to see what's going on.
__________________

smac999 is offline   Reply With Quote
Old 27-09-2018, 16:05   #3
Moderator
 
Paul Elliott's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Posts: 4,516
Images: 4
Re: Intermittent AIS signal

Where are you located? Class-B AIS essentially uses timeslots that are left over after all the Class-A transponders transmit. So it's possible that you are being shut out by a lot of Class-A traffic. But this is pretty rare, and if other nearby Class-B transponders aren't showing the same behavior smac999 (above) is probably correct.
__________________
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
www.sailvalis.com
Paul Elliott is offline   Reply With Quote
Old 28-09-2018, 13:31   #4
Senior Cruiser
 
svMarite's Avatar

Cruisers Forum Supporter

Join Date: Jul 2012
Location: Chesapeake Bay
Boat: Shannon 43 Ketch
Posts: 83
Re: Intermittent AIS signal

What jumped out at me was the comment "10 yrs", check connections for corrosion, especially clean antenna connectors as carbon has probably built up, a pencil eraser works well.
Next is the CG just published a study of LED interference, check that too
__________________
Smooth sailing and fresh warm breezes,
Tony & Lisa
sv Marite
'87 Shannon 43' Ketch
svMarite is offline   Reply With Quote
Old 28-09-2018, 13:53   #5
Moderator
 
Paul Elliott's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Posts: 4,516
Images: 4
Re: Intermittent AIS signal

Quote:
Originally Posted by svMarite View Post
What jumped out at me was the comment "10 yrs", check connections for corrosion, especially clean antenna connectors as carbon has probably built up, a pencil eraser works well.
Next is the CG just published a study of LED interference, check that too
LED interference will affect reception, but not transmission of AIS (or any radio signal.)

Here's that USCG report: https://www.dco.uscg.mil/Portals/9/D...-16-091109-630

Good info, but it's what we've been saying here for years.
__________________
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
www.sailvalis.com
Paul Elliott is offline   Reply With Quote
Old 28-09-2018, 18:39   #6
Senior Cruiser

Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 17,655
Re: Intermittent AIS signal

If it was OK before but is not any more then a bad cable / connector or antenna may be the fault. Check one item at a time and test.


It is very easy to rig another antenna with a new piece of cable and new connectors and test this by just running the cable out of the hatch and onto the rail.


Let us know how it goes.


b.
barnakiel is offline   Reply With Quote
Old 02-10-2018, 04:59   #7
Registered User
 
clownfishsydney's Avatar

Join Date: Mar 2014
Location: Sydney, Australia
Boat: Lightwave 38' Catamaran
Posts: 385
Re: Intermittent AIS signal

I have seen this with other boats, disappearing, then appearing, over and over again all day as we sail near each other. No idea what AIS they have, but it certainly was not caused by congestion.
__________________
Michael
Catlypso - Web Site
Lightwave 38' cat
clownfishsydney is offline   Reply With Quote
Old 02-10-2018, 16:06   #8
Registered User
 
River Cruiser's Avatar

Join Date: Jul 2011
Location: UMR mm 283 /winter in Kansas
Boat: Bayliner 3870 41' oal.
Posts: 884
Re: Intermittent AIS signal

My class B will transmit once every 2 minutes while cruising, normal speed is 6 to 7 mph. I have 2 mfd on the flybridge one is connected to my SH GX2150 vhf, that one picks up the transmission and the icon moves to the boat position icon. Then as I move the AIS icon remains stationary until the next transmission and it jumps ahead.
River Cruiser is offline   Reply With Quote
Old 02-10-2018, 18:25   #9
Moderator
 
Jim Cate's Avatar

Join Date: May 2008
Location: cruising SW Pacific
Boat: Jon Sayer 1-off 46 ft fract rig sloop strip plank in W Red Cedar
Posts: 13,891
Re: Intermittent AIS signal

Quote:
Originally Posted by River Cruiser View Post
My class B will transmit once every 2 minutes while cruising, normal speed is 6 to 7 mph. I have 2 mfd on the flybridge one is connected to my SH GX2150 vhf, that one picks up the transmission and the icon moves to the boat position icon. Then as I move the AIS icon remains stationary until the next transmission and it jumps ahead.
I believe that at such speeds a class B should transmit every 30 seconds. Mine (Vesper Vision) does, and so do all the others I see on my display.

Jim
__________________
Jim and Ann s/v Insatiable II lying Sandy Bay, Hobart,
Jim Cate is offline   Reply With Quote
Old 02-10-2018, 23:41   #10
Moderator
 
Paul Elliott's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Posts: 4,516
Images: 4
Re: Intermittent AIS signal

Quote:
Originally Posted by Jim Cate View Post
I believe that at such speeds a class B should transmit every 30 seconds. Mine (Vesper Vision) does, and so do all the others I see on my display.
  • 0-2 kts: every 3 minutes
  • Greater than 2 kts: every 30 seconds
__________________
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
www.sailvalis.com
Paul Elliott is offline   Reply With Quote
Old 04-10-2018, 15:53   #11
Registered User
 
River Cruiser's Avatar

Join Date: Jul 2011
Location: UMR mm 283 /winter in Kansas
Boat: Bayliner 3870 41' oal.
Posts: 884
Re: Intermittent AIS signal

I probably go slow enough at times to be in the 3 minute group puting along against the current
River Cruiser is offline   Reply With Quote
Old 06-10-2018, 00:36   #12
Registered User
 
Sir_Crabs_A_Lot's Avatar

Join Date: Sep 2018
Location: Washington State
Boat: Steamboat, 25 ft
Posts: 63
Images: 1
Re: Intermittent AIS signal

The signal from a VHF antenna spreads out horizontally, so on a sailboat that's heeled, one side will shoot up in the air and the opposite side into the water. This might be why it drops out intermittently, but is ok at the dock?
__________________
"Science, my lad, is made up of mistakes, but they are mistakes which
it is useful to make, because they lead little by little to the truth" - Jules Verne
Sir_Crabs_A_Lot is offline   Reply With Quote
Old 06-10-2018, 04:09   #13
Moderator
 
Jim Cate's Avatar

Join Date: May 2008
Location: cruising SW Pacific
Boat: Jon Sayer 1-off 46 ft fract rig sloop strip plank in W Red Cedar
Posts: 13,891
Re: Intermittent AIS signal

Quote:
Originally Posted by Sir_Crabs_A_Lot View Post
The signal from a VHF antenna spreads out horizontally, so on a sailboat that's heeled, one side will shoot up in the air and the opposite side into the water. This might be why it drops out intermittently, but is ok at the dock?
typical low gain sailboat antennae are not subject to this effect. There must be another source.

Jim
__________________

__________________
Jim and Ann s/v Insatiable II lying Sandy Bay, Hobart,
Jim Cate is offline   Reply With Quote
Reply

Tags
ais

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Weak AIS Signal? theway Marine Electronics 56 10-05-2018 15:09
McMurdo vs Ocean Signal MOB AIS comparison? Dr. Sea General Sailing Forum 34 13-03-2016 17:23
Receiving AIS Signal ? gleff Marine Electronics 17 23-01-2012 03:32
Getting AIS rs-422 Signal Out to the iPad PeregrineSea Navigation 3 26-07-2011 09:52
AIS Signal Splitter to 2 Laptops Colin Stone OpenCPN 6 16-04-2011 16:53



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 07:28.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.