DSC - Is it all its cracked up to be?

[martini]

Originally Posted by gotchiguy

You would be able to do this however not really practical seeing as AIS range on a RIB is only 10nm absolute tops. Best thing to do is just program them all into your phone book on the drive at home

AIS range is going to be the same VHF voice no?

Sent from my portable speaking device using Rib.net

[gotchiguy]

Originally Posted by martini

AIS range is going to be the same VHF voice no?

Sent from my portable speaking device using Rib.net

No I don't think so. Erin told me that between La Frette and MII you only see each other at 3nm....surely VHF range would be twice if not three times that?

[Erin]

Originally Posted by gotchiguy

No I don't think so. Erin told me that between La Frette and MII you only see each other at 3nm....surely VHF range would be twice if not three times that?

I suspect it should be better than that and I plan on fitting a better aerial to see. Boat to base station is regularly over 30 nm.

[redthunder]

We regularly pick up AIS signals over 35 miles away on our rib. Sometimes a lot more.

[hobbit555]

I think dsc is a fantastic system and I use it all the time. The problem is however that I think some radios are not user friendly and as such make it very time consuming to make dsc calls. I use it professionally between our vessels especially when talking business. It stops all those prying ears. One bug bear I do have is using coastguard stAtions for radio checks when a marina office, vts or another nearby vessel could be used instead

[Cookee]

Originally Posted by hobbit555

I use it professionally between our vessels especially when talking business. It stops all those prying ears.

How does it make your voice communications private?

[SPR]

Originally Posted by Cookee

How does it make your voice communications private?

it does not! only thing it stops is somebody switching to that ch. after hearing it being announced on ch. 16.

VHF Radio is for essential traffic only.

If you don't need to transmit don't transmit - either use mobile phone or PMR or Private Ch. for non essential conversations.

We all sign confidential agreements when we get out licence - since VHF is an open system.


S.

[DGR]

Originally Posted by ShinyShoe

CG stations have AIS - so can you point and click them?

Originally Posted by gotchiguy

You would be able to do this however not really practical seeing as AIS range on a RIB is only 10nm absolute tops. Best thing to do is just program them all into your phone book on the drive at home

Originally Posted by martini

AIS range is going to be the same VHF voice no?

Not always - you'll probably be speaking to the Coastguard through a local repeater aerial - rather than the one on the watchroom roof - so direct AIS range and VHF range aren't the same thing.

That's why you can often hear the Coastguard talking clearly to someone on the other side of their patch - but you can't hear the reply (unless it's the rescue helo - which is different again!!).

[hobbit555]

Originally Posted by Cookee

How does it make your voice communications private?

If I don't announce a working channel then only the vessel that I dsc knows what channel I will broadcast on. But then I suppose there are those muppets who scan every channel all the time as opposed to tag scanning useful channels.

[martini]

Originally Posted by gotchiguy

No I don't think so. Erin told me that between La Frette and MII you only see each other at 3nm....surely VHF range would be twice if not three times that?

Originally Posted by Erin

I suspect it should be better than that and I plan on fitting a better aerial to see. Boat to base station is regularly over 30 nm.

I had always assumed that AIS range would be the same as VHF since you are using the same system with same antenna etc but thinking more about it prompted me to check what sort of power AIS systems transmit at, I always assumed it was the standard 25W.

Most manufacturers don't seem to advertise this in there specs but a standard has been set, for class A systems the output is only 12.5W and for class B it's a measly 2W.

This would explain why 2 ribs with class B and comparatively low antennas don't see each other until fairly close.

But then it wasn't designed for seeing where your mates are at, it's for collision avoidance so the range doesn't need to be huge.

Apologies for drifting the thread from DSC to AIS but thought it was worth a mention in case others hadn't realised the limited power.

[willk]

Still, a mobie is only pushing out, what? 1 watt? That and AIS being a short digital data message would make one assume that the range would be greater than 3Nm. You weren't switching your's off to dodge Erin again, were you Martini?

[ShinyShoe]

Handheld VHF is 5 or 6W max in high power.

[Erin]

Originally Posted by willk

You weren't switching your's off to dodge Erin again, were you Martini?

He can't hide. You can hear his Opti's well before AIS kicks in

He made a good point about the 2W output though. I hadn't considered that.

[gotchiguy]

Originally Posted by Erin

He made a good point about the 2W output though. I hadn't considered that.

Just as surprising that class A is only 12.5W too, coming back from Cherbourg we saw the Bretagne way before it came up on AIS

[martini]

Originally Posted by gotchiguy

Just as surprising that class A is only 12.5W too, coming back from Cherbourg we saw the Bretagne way before it came up on AIS

And what height is the antenna on that??

That's what it's all about

Sent from my portable speaking device using Rib.net

[willk]

Originally Posted by ShinyShoe

Handheld VHF is 5 or 6W max in high power.

Yes, but a mobile (phone) is around 1w - or so I'm told. It's not a particularly relevant observation on my part, just that a small handheld 1w phone with no meaningful antenna can send a text message quite a few miles...

[Erin]

Originally Posted by willk

Yes, but a mobile (phone) is around 1w - or so I'm told. It's not a particularly relevant observation on my part, just that a small handheld 1w phone with no meaningful antenna can send a text message quite a few miles...

Yes, but that's not mobile to mobile, it's mobile to f###-off big aerial with high sensitivity tuned receiver.

[al_typeR]

As has already been said the number of DSC. calls against the number of voice calls received at any of the Coastguard stations is hugely disproportionate. I also agree that the user interface on some DSC radios are less than friendly and the biggest problem is no 2 are the same not even 2 from the same manufacturer. The biggest trouble is the number of false alarms with DSC. about 96% of all received are false alarms largely down to operator error.

So is DSC worth it? My answer is yes but only once you are trained and have read the manual and worked out how to use it. For getting the coastguards attention there is nothing better as often on a busy summers day when multiple vessels all call together on channel 16 it is impossible to hear them all by voice. But each DSC is seen as a separate message. As for radio checks there is no need to call the coastguard. A radio check with your local port or marina is just as good and takes some of the pressure off the poor coastguard who is trying to hear the vessels calling through the din ( high pressure often gives us over 500 miles VHF range from some of our aerials).

Finally traffic reports. If you know all this then I apologise but many simply do not. When the Coastguard in the UK take your traffic many are under the misconception that we monitor your progress and if we don't hear from you we will start looking. The reality is it goes into a radio log and nothing more happens. If you keep in mind on a busy weekend hundreds of reports are received by Solent alone you can understand why. The idea is you register on the CH66 scheme and part of that is nominating a shore contact. This is someone who stays shoreside ( so a friend or relative who had no sea legs) and tell them when and where your going and agree to contact them on arrival. If you don't contact then they call the coastguard and we then start looking for you. That way should the worst happen we know all about you, we know from your shore contact where you were going and we know something is up.

Sorry for this being so long winded but I hope it clears it up a little.

[SPR]

thanks for that - 7 days before we lose Forth Coastguard - last transmission is 1330 hrs UTC/GMT from Fifeness 109 years of service.

S.

[ShinyShoe]

Originally Posted by al_typeR

about 96% of all received are false alarms largely down to operator error.

Is that 96% are not in any form of trouble or 96% send a Distress Alert when they should have sent an urgency?

Originally Posted by al_typeR

So is DSC worth it?

Originally Posted by al_typeR

For getting the coastguards attention there is nothing better as often on a busy summers day when multiple vessels all call together on channel 16 it is impossible to hear them all by voice. But each DSC is seen as a separate message.

So are you advocating it for routine type traffic or just distress?

Originally Posted by al_typeR

When the Coastguard in the UK take your traffic many are under the misconception that we monitor your progress and if we don't hear from you we will start looking.

I think thats one of the issues... people think you will because you seem happy to take them. You ask lots of questions about number of people type of vessel etc. So lets say I file a plan with you. My shore contact calls in to say I haven't called home to say I'm safe - what links that to my passage plan I called you with? My shore contact could be my parents 300 miles away, with zero boating knowledge. They'd know I had a "speedboat" that its grey and has an outboard engine. They'd know its name coz I've told them and you'd find a CG66 for it. I've told them I'm going from Sea Houses to the Farnes with a couple of friends, but if its too windy we'll go to Holy Island... If you could link to my call you'd know I only have 2 POB (1 of my friends cancelled last minute) and I definately was headed to the Farnes (you might even know which island!), and you'd know I was 45 minutes late leaving but I haven't told my parents that. Would I have been better calling my parents than calling the CG at all?