Navy and AIS

[westhinder]

When crossing Biscay from Galicia to Brittany a couple of days ago, we came across a number of NATO warships on exercise, firing live ammunition. None of these ships transmitted AIS. At the same time we noticed our AIS reception was noticeably poorer than normal. It was only as we closed the French coast that normal AIS reception was resumed.
Do warships have the capability to jam AIS? If so, is it acceptable to use that in peacetime and affect innocent passers-by? We sailed into a dense fogbank with poor AIS reception, which is not my idea of fun.

 

[pvb]

We sailed into a dense fogbank with poor AIS reception, which is not my idea of fun.

It's called "character building".

 

[EdWingfield]

Do you really expect warships on exercise to broadcast what they are doing?

 

[Tomahawk]

I would prefer they did if ther are firing live munitions.

 

[Quandary]

They have a major exercise up here around the Clyde and the west coast every spring, I like to follow it on AIS but it always seemed odd that they broadcast it, must make it very easy for the 'enemy force' to find them.

 

[AngusMcDoon]

They have a major exercise up here around the Clyde and the west coast every spring, I like to follow it on AIS but it always seemed odd that they broadcast it, must make it very easy for the 'enemy force' to find them.

I expect that they can switch it off in the event of the Germans getting uppity again.

 

[westhinder]

Do you really expect warships on exercise to broadcast what they are doing?

No, I don’t, but that was not the point. I was mainly wondering whether the odd behaviour of our AIS reception was caused by warships actively jamming AIS. If that is the case I am not too happy about that.

 

[vyv_cox]

There are many warships patrolling the waters between Greece and Turkey. Many do not transmit anything on AIS but we have seen one or two that do, using the code 9999999

 

[bedouin]

I can't imagine the Navy deliberately jamming AIS, what would that achieve?

I suppose it is possible they had other electronic equipment that was causing interference.

 

[mainsail1]

I think it is very unlikely that those warships had anything to do with your poor AIS reception. Radio frequencies are prone to have variable quality reception/transmit areas depending on a wide range of circumstances.

 

[johnalison]

It is often entertaining to hear Dover Coastguard asking warships for details of their passage through the straits and getting brusque replies.

 

[capnsensible]

Until AIS was invented, there was no such thing as ships.

 

[jeff3]

Doesn't our ais get bounced of bigger ships broadcast to a ground on land if a warship hasn't theirs on then it's poor reception

 

[prv]

At least in the UK, exercises involving GPS jamming and similar activities are published as Notices to Mariners. They happen reasonably often up in Scotland and occasionally elsewhere. I don't know where you'd find an equivalent, if it exists, for Biscay.

I've not heard of AIS jamming specifically. I imagine they can, but also that if they really meant to, your little leisure set's reception wouldn't just be "poorer than normal", but completely blocked. Maybe there was some other electromagnetic activity going on that incidentally had a minor effect on AIS frequencies?

Doesn't our ais get bounced of bigger ships broadcast to a ground on land

No.

Pete

 

[NormanS]

Doesn't our ais get bounced of bigger ships broadcast to a ground on land if a warship hasn't theirs on then it's poor reception

Eh?

 

[Roberto]

I don't know where you'd find an equivalent, if it exists, for Biscay.

Offshore live firing exercises are indicated here, example:
https://www.premar-atlantique.gouv.fr/avis-urgents-aux-navigateurs/yeu-armorique-5d9dc08eca930
they are also sent on Navtex.
The areas are standard and appear in the Sailing Directions

 

[PilotWolf]

Don't know about jamming but the last time I was in the Solent they were spoofing things both at sea and ashore...

W.

 

[Giblets]

We sailed into a dense fogbank with poor AIS reception, which is not my idea of fun.

I don't suppose your AIS reception could have been hampered by the dense fog bank. Used to happen regularly with Decca Navigators in such conditions. Perhaps radar would have been more effective.

 

[prv]

I don't suppose your AIS reception could have been hampered by the dense fog bank. Used to happen regularly with Decca Navigators in such conditions.

I've never heard of fog affecting VHF, which is a more reasonable comparison.

Pete

 

[LadyInBed]

I don't suppose your AIS reception could have been hampered by the dense fog bank. Used to happen regularly with Decca Navigators in such conditions. Perhaps radar would have been more effective.

I've never heard of fog affecting VHF, which is a more reasonable comparison.

Pete

Water on the antenna could degrade the signal level, but also I wouldn't be surprised that warships have the ability to swamp VHF around them.
Back in the day, I once passed a warship in Portland harbour and I lost my DECCA position and all my waypoints got wiped out.