[B]Combined VHF/AIS Problem[/B]

[BillHerc]

Have just had my IC-M506 marine band radio/AIS repaired.

It now does not receive AIS data from any local yachts but does receive commercial traffic out to 20nm +.

I note there are 2 designations for AIS transponders, A & B.

I am unable to find in the settings menu anywhere to access a switch that could revert my radio to its previous ability to receive yachts.

Any ideas?

 

[knuterikt]

I don’t think that you will find a setting to filter class B,
how do you know that you are missing class B?

 

[BillHerc]

I don’t think that you will find a setting to filter class B,
how do you know that you are missing class B?

I know I'm missing class B as I can't receive friends' yachts transmission (very close) but do receive 'commercial' traffic out to 20nm +. I am, of course, assuming that the yachst (30-40ft) are using class B transponders. They can be picked up on my mobile but not my AIS eqiupped VHF!

 

[knuterikt]

I know I'm missing class B as I can't receive friends' yachts transmission (very close) but do receive 'commercial' traffic out to 20nm +. I am, of course, assuming that the yachst (30-40ft) are using class B transponders. They can be picked up on my mobile but not my AIS eqiupped VHF!

what you see on your mobile is not real time, Data can shown long after AIS is turned off.

edit:
browsed the manual, only filter option is on MMSI.
You should talk to a friend to verify that they are transmitting.

 

[lw395]

If you do find out how to make it lose class B, please let us know!

 

[Seven Spades]

It sounds to me as though when it was serviced it has been set that way. I would call the manufacturer.

 

[BillHerc]

Yes, I am trying to get manufacturer. Re comment about time delay in displaying on AIS websites. There is little delay in fact. I tracked my friend, 3 or 4 nm behind me all the way across the Moray Firth (sounds good, only 20nm) with no problem on mobile phone but nothing on my AIS, although non yacht traffic (in as many as I checked) were showing up 20nm + no problem. Even a transmitting yacht beside me in the marina is not received. Is DSC, MMSI tied up with this in any way?
This worked correctly before it was sent for repair (different problem).

 

[matthewriches]

iCom UK are very helpful, just in case that isn’t who repaired your unit. 01227 741741. A lot of the tech guys are fellow amateur radio operators so generally know their onions.

 

[BillHerc]

Thanks very much for that. The expert is away till tomorrow so I'll contact them and no doubt get to the bottom of this.
Thanks again! Will let you know.

 

[BillHerc]

Thanks very much for that. The expert is away till tomorrow so I'll contact them and no doubt get to the bottom of this.
Thanks again! Will let you know.

Here is the reply from my local agent who spoke to them:

There’s no reason he can think of why the unit would receive one class of AIS and not the other, (he went away and checked all his tech documentation before he phoned me back!) however he did say that it might be a “polling” thing as the commercial AIS telegrams always take priority and the leisure AIS basically has to “wait on a slot” to get it’s signal in. depending on how much commercial traffic was going about it might be that the unit was not listening on that band when a slot became available as it were, so could take 20minutes or more for a leisure AIS to pop up. – In busy shipping lanes the commercial traffic AIS is “controlled” but up here were not that busy so it could be just demanding all the slots (depending on who it is and how it’s set up as well).

So question is how long did you have it on with a known leisure AIS transmitting in range of you? – if more than 20 minutes we maybe need to look at it again, if less it might just be an anomaly on the day, but the way AIS works it’s possible!



I had it on for several hours with my friend quite close behind.

The plot thickens ...