pvb
Well-known member
I'm not convinced that a yacht running into you necessarily would be the end of your world, whereas a ship running into you might seriously spoil your day! So the active radar enhancer is surely a safer bet?
AIS transmitter or Radar Enhancer?
- Thread starter doug748
- Start date
I'm not convinced that a yacht running into you necessarily would be the end of your world, whereas a ship running into you might seriously spoil your day! So the active radar enhancer is surely a safer bet?
Topcat47
Well-known member
A watch keeper looking at his PPI will notice an AIS plot when he might miss a simple Radar echo. A small boat's radar signature mat be lost in clutter or even filtered out by anti-clutter software. A radar transponder response is less likely to be lost like this, but a plot with a course and heading notated is bound to be more noticeable than a simple echo, IMHO. Similarly, if you have an AIS transceiver, you can see where vessels are and in what direction and how fast they are approaching (assuming they have active AIS). Anyone who follows my posts on the subject, knows I'm no fan of reliance on electronic aids in small boats, but if that's the options you're considering, I'd always go for AIS first. At least it's possible to support an AIS for longer with a decent battery bank on a small yacht.
RichardS
N/A
Although I'm not sure that an active radar enhancer is that much more battery-unfriendly than an AIS transmitter. It might have even been covered above.
Having been faced with this choice exactly I decided to get the AIS transceiver first and then follow-up with the EchoMax. Having lived with the AIS for a year (fog-free Med rather than Solent) I'm not going to bother with the EchoMax.
Richard
LadyInBed
Well-known member
You will see a ship on your own AIS receiver, as he transmits, so you can initiate some action.
Consider it from the point of view as you being 'the ship' and a yacht heading your way sans Radar but with AIS Rx.
He will see your AIS Tx and he can initiate some action.
Javelin
Well-known member
I was having a chat with a tanker first mate the other day and he said that the only issue with ais is clutter around port entry and exits and that they routinely turn off various types to improve clarity.
However he also said they turn them all back on as soon as they are out to sea.
As has been said before the ais transmitter gives heading speed and other info without any effort as opposed to the radar which has to be interpreted.
They also use the tracking information on the ais as well to help with predictions.
He said that if they hit something or had a near miss on a vessel that was transmitting ais position data they would have a much harder time explaining themselves than if it was just a radar contact.
Also my ais is linked to the vhf and last year I received 2 direct vhf calls from other vessels using the msi number and ais data, asking me my intentions as I approached shipping lanes off Belgium and then off Holland.
However he also said they turn them all back on as soon as they are out to sea.
As has been said before the ais transmitter gives heading speed and other info without any effort as opposed to the radar which has to be interpreted.
They also use the tracking information on the ais as well to help with predictions.
He said that if they hit something or had a near miss on a vessel that was transmitting ais position data they would have a much harder time explaining themselves than if it was just a radar contact.
Also my ais is linked to the vhf and last year I received 2 direct vhf calls from other vessels using the msi number and ais data, asking me my intentions as I approached shipping lanes off Belgium and then off Holland.
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dslittle
Well-known member
This is also my understanding and rationale for having an AIS Transceiver. There is also the comfort blanket of being able to 'see' what the big boys are doing (which the best radar reflector/enhancer doesn't)
pvb
Well-known member
You don't need an AIS transceiver to be able to monitor ships, just a receiver.
Topcat47
Well-known member
Most large ships trundle up and down at around 20-25knots. They have a large turning circles and poor brakes. My yacht has a top speed of 6 knots max. Even in good vis I am wary of large ships but in poor vis, I'd prefer to know what they're doing AND them to know what I'm doing. Were Money and battery power more plentiful on my boat, I'd go for the transceiver over a simple receiver. I'd not be without my Radar reflector and VHF though.
dslittle
Well-known member
Errr. I know that and I suspect that the OP does as he already has a receiver!!!
DJE
Well-known member
Planning to install an AIS transponder as my next upgrade. But the boat does not have DSC or an MMSI - just old fashioned vhf. Is this a problem?
dom
Well-known member
Lack of DSC is no prob, but 99% sure you'll need an MMSI.
prv
Well-known member
An AIS transmitter requires an MMSI.
The MMSI identifies the boat, not any particular equipment. For most people, the first thing they get that uses one is a DSC VHF, but I don't think there's any theoretical reason that that has to be so. In your position I would go to the Ofcom site and try modifying my license (which you need to do anyway to add the AIS); if the MMSI field is left blank it might generate a new one for you. If not, I would cancel the existing license and take out a new one, in this situation it definitely assigns a new MMSI if you leave the field blank.
Other thing to note - people seeing you on AIS and wanting to communicate might do a DSC call to your MMSI, which won't get through if you don't have a DSC VHF. But in practice I think most commercial shipping still does voice calls on 16 using just the name from AIS, and even if someone starts with DSC they would probably try voice if there's no answer.
Pete
navrep
Member
Out of the two I would definitely go for the transceiver - as pointed out earlier it is the big boys you are really wanting to let know who you are and what you are doing and for that AIS is the better tool, no guarantee that smaller yachts/boats
a) have radar,
b) know how to use it properly.
When crossing shipping lanes I like to know what I am trying to avoid and that they know who and what I am. Calling a vessel by name is a darn site quicker than "vessel at position ....." and with container ships going in excess at 20nkts time is of the essence.
On my recently bought yacht which currently doesn't have any AIS I am about to buy a transceiver - Raymarine AIS650 Class B Transceiver + splitter so it will all talk to the E7 plotter.
a) have radar,
b) know how to use it properly.
When crossing shipping lanes I like to know what I am trying to avoid and that they know who and what I am. Calling a vessel by name is a darn site quicker than "vessel at position ....." and with container ships going in excess at 20nkts time is of the essence.
On my recently bought yacht which currently doesn't have any AIS I am about to buy a transceiver - Raymarine AIS650 Class B Transceiver + splitter so it will all talk to the E7 plotter.
Bru
Well-known member
No, simply apply for a new ship's VHF licence online listing a non-existent DSC VHF and an MMSI number will be allocated
However, given that a DSC VHF can be purchased for the price of a good night out, I'd strongly suggest upgrading the VHF to DSC if only for the big red panic button
LadyInBed
Well-known member
Re MMSI, there is no rule that AIS Tx has to be programmed with it.
You can request one if you wish, but I think it would be counterproductive to display an MMSI No if you don't have a programmed DSC VHF. You would be pinged in vain.
I don't know what alpha numeric format the AIS will accept when programmed with MMSI, but if it is quite loose you could put in NO or N(zero) if you did not want to leave it blank.
You can request one if you wish, but I think it would be counterproductive to display an MMSI No if you don't have a programmed DSC VHF. You would be pinged in vain.
I don't know what alpha numeric format the AIS will accept when programmed with MMSI, but if it is quite loose you could put in NO or N(zero) if you did not want to leave it blank.
prv
Well-known member
Errm, yes there is. The MMSI is how the transmissions are identified, how the receiver knows that the various different messages it receives relate to the same boat. Your comment is like saying "there's no rule saying you have to have a telephone number just because you have a telephone" - the system absolutely will not work without one, so until you provide it the transmitter will not transmit. And I very much doubt it will accept a completely invalid format like you suggest because it wouldn't be able to properly encode it for transmission.
You could, I suppose, put in a made up number, but why bother when it's free and easy to obtain a real one? If you didn't use the right prefix you would appear to be of a different nationality, you might be purporting to be a Coastguard station or a distress beacon if you happened to pick the right (wrong) numbers, and even if you get the format right to appear as a British yacht, there's the potential for confusion when you report as being someone else, which will be very obvious if they or their friends ever look themselves up on MarineTraffic or similar.
Sorry, this is all a very silly idea, and probably against the terms of your VHF license to boot.
Pete
LadyInBed
Well-known member
I take it that this is all speculation as you didn't put in a link to any rule or regulation.
What you describe is apposite to DSC VHF, nothing to do with the subject under discussion - AIS Tx
As much as some people like DSC, I don't, so even if I were to install a DSC capable VHF, I wouldn't request or program the set with an MMSI #
so to put out an MMSI # on AIS is pointless.
I only suggest putting NO in the AIS MMSI field as a possibility, my personal inclination would be to leave it blank.
Bru
Well-known member
PRV is absolutely correct. Class B AIS TX will not function without a valid MMSI number. Programming an invalid number would be both stupid and illegal
I don't understand the objection to DSC VHF either - you don't have to use the calling functions if you don't want to but the digital mayday function alone is worth having
I don't understand the objection to DSC VHF either - you don't have to use the calling functions if you don't want to but the digital mayday function alone is worth having
pvb
Well-known member
You don't know much about AIS, do you? Check out this link https://www.itu.int/dms_pubrec/itu-r/rec/m/R-REC-M.1371-5-201402-I!!PDF-E.pdf and read para 3.
BrianH
Active member
But the MMSI is the key that identifies all the target reports from a transmitter that the receivers process. A slot is opened as soon as the first report is received and updated by matching the MMSI in the target list as each and every subsequent report is received. It also matches dynamic and static data sentences, which are transmitted separately, to update the target list.
For a vessel the first numeric characters identify your registered country and the rest your discrete identity. I suspect anything that contravenes that protocol will not constitute a valid identifier and unlikely to be sent. It will certainly confuse all receiving stations.