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EPIRB Update

 SART Last year I did a quick summary of the EPIRB products then available because I had come to replace my old 121Mhz EPIRB.

The 406 MHz units were designed specifically for satellite detection and Doppler location, and provide the following:

  • improved location accuracy and ambiguity resolution;
  • increased system capacity (i.e. capability to process a greater number of beacons transmitting simultaneously in field of view of satellite);
  • increased probability of detection (higher power);
  • global coverage; and
  • unique identification of each beacon.

System performance is greatly enhanced both by the improved frequency stability of the 406 MHz units and by operation at a dedicated frequency.

These beacons transmit a 5 Watt RF burst of approximately 0.5 seconds duration every 50 seconds. The carrier frequency is very stable and is phase-modulated with a digital message. Frequency stability ensures accurate location, while the high peak power increases the probability of detection.

For a treatise on the whole Search and Rescue topic you need go no further than good old Wikipedia of course, and it was here that I looked for explanations of what legal or international standards our EPIRB products should adhere to. They all seem to claim a variety of compliance certificates! The definitive list of standards can be found on the actual COSPAS-SARSAT web site here.

Also, when it comes to the actual operation of the SAR service, training, response type etc…there is also some international variability according to this Wikipedia article ….”…With or without formal underlying foundations, numerous SAR organisations develop their own proprietary training curricula and operational protocols, which are available and applicable only to their own members.  In the US SAR standards are developed primarily by ASTM International and the US NFPA which are then used by organizations such as the Mountain Rescue Association (MRA), the US National Association of Search and Rescue (NASAR), and the US NFPA to develop training that will meet or exceed those standards. Within ASTM International, most standards of relevance to SAR are developed by Committee F32 on Search and Rescue. Formed in 1988, the committee had 85 current members and jurisdiction of 38  approved standards. ….”

Obviously you will want to get your EPIRB registered – something that most good dealers will do for you. If you are in doubt then I recommend looking at the excellent COSPAS-SARSAT web site FAQ’s for information about your country’s registration process and the unique country code identifiers.




You will also want to buy an EPIRB that has the correct approvals – not just a long list of acronyms that look impressive – again check out COSPAS-SARSAT – they provide a list of products by manufacturer here.

From this web site it is of note that:

  • A particular beacon model may be sold under several different names. All alternative beacon model names provided to the Cospas-Sarsat Secretariat by the beacon manufacturer are listed in the detailed report. Detailed reports can be accessed via the table listing beacon models by Cospas-Sarsat type approval number.
  • Some manufacturers use the same beacon model names for beacons with different type approval numbers.
  • Cospas-Sarsat Numbers (No.) starting at 700 identify special use beacons. These beacon models are compatible with the Cospas-Sarsat System; however, they do not satisfy all Cospas-Sarsat technical and testing requirements as detailed in Cospas-Sarsat documents C/S T.001 (406 MHz beacon specification) and T.007 (406 MHz beacon type approval standard). Therefore, they have not received a Cospas-Sarsat Type Approval Certificate.
  • In the maritime domain, EPIRBs are designated as either float free (FF) or a non-float free (Non FF). FF EPIRBs are designed to float away from a sinking vessel and activate automatically, whereas Non FF EPIRBs can only be activated manually.

I am ashamed to say that I didn’t actually get round to replacing my old EPIRB –  so I am looking once more at the options on the market, and have whittled it down to three possible contenders. So I looked them up on the COSPAS-SARSAT web site for approved products, to see if they had actually got the correct approvals…

  1. McMurdo Smartfind Plus G5 406 MHz GPS EPIRB – COSPAS-SARSAT report here

Thankfully the three I had shortlisted appeared to be correctly approved, including the excellent Australian GME products.

To download a PDF of my comparison chart click here….


Buy Raymarine AIS500 or buy £800 of Raymarine shares?

AIS500 I applaud Raymarine for having brought this unit out earlier this year, it is good product marketing and market positioning (pun intended:-)

But if you already have a reasonably sophisticated set up, and already have AIS, is it worth spending £800+ to upgrade to this unit?

Here is my take on the list of features for the AIS500:

Feature Comment
* Class B AIS Receive & Transmit Good – and so do all the competition at this level
* Dual Channel AIS Monitoring Ability Good – and so do all the competition at this level
* Targets displayed on chart and radar screens Clever – but I normally overlay radar on the chart plotter or display AIS targets on the chart rather than the radar which could be very confusing if not misleading due to the different methods of target acquisition
* LED Status Indicator Good – Surprising omission on so many marine electronics and very annoying when there is no status light and you are troubleshooting.
See my posting here on the RaymarineAIS250
* NMEA 0183 – Compatibility with Raymarine A, C, E and G Series Good – the great majority of Raymarine users must be on C series (or lower) still.
* Buddy Tracking via Raymarine MFD – Distinguish favourite targets (MMSIs) from others by adding to favourite list Clever – but is this really needed – oh ok could stave off boredom in some situations to switch between “favourites” and “all” targets. In between calling your buddy on the radio…
* Silent Mode – Turn off transmit function during tournaments or races if you do not wish to be seen. Good – But only if you expect to be sailing in regions where piracy is possible – not really a problem in the Solent – yet!
I did refer to this as a good thing in my posting here:-)
* Built-in NMEA multiplexor Not Good – I have a principle of using separate dedicated pieces of electronics instead of multifunction devices ion this situation. A faulty multiplexor can take down the whole backbone and all links between devices I would not want to troubleshoot that with a device that was doing so much else as well.
See my posting here on multiplexors.
* VHF Splitter – No need to buy a separate antenna. Utilize your existing VHF antenna and cable. Not good – don’t use splitters on your VHF cable!. keep the radio and its aerial as separate as possible. Yes I know that DSC has meant connecting the VHF to the NMEA circuit – but just don’t mess with the VHF aerial. This is a critical lifeline. Install a separate VHF aerial for AIS on the pushpit IMHO.
* Includes dedicated external GPS antenna (16 channels) Not good – as per comment above. Keep the GPS separate, you probably already have one, get another one for backup don’t get one built in to another multifunction device.
* Configure via PC Software
* Software upgradeable through PC and RS232
Ok – but why use serial connections and then very probably a serial to USB convertor when you can use high speed USB. Most modern laptops don’t even have serial ports
See my posting here on serial / USB convertors

I last did a quick survey of transponders (or are they transceivers) in June 2008, but I have held off updating this since I believe that we can expect another revolution in AIS for small boats in the next 6 months.

On that basis I would not buy the AIS500 now, if you already have AIS – if you don?t – then it is a very capable unit with the benefit of a back up GPS.

If you already have AIS and you want to spend £800 buy Raymarine shares, if you made 30% profit when Garmin buy them, that would be an extra £240 to spend on the next generation AIS – then again shares can go down as well as up:-)


Taking the ‘search’ out of Search and Rescue

A bit late in the day I have been researching replacements for my Class B 121.5Mhz EPIRB which will be relegated to the grab bag and used as a PLB (Personal Locator Beacon) in an emergency. Cospas-Sarsat ceased satellite processing of 121.5/243 MHz beacons 1 February 2009. These beacons will only be able to be detected by ground-based receivers and aircraft for example actually engaged in a SAR operation that had been initiated using the new systems.

A bit of internet research reminded me that the old analog system was accurate to around 20km (10.8nm) and that a SAR (search and rescue) operation would only be launched after two satellite passes – which could mean a delay of about 2 to 3 hours, often it would take 6 hrs to resolve the location by using multiple passes of the weather satellites system. The other factor to note is that the old 121.5Mhz system transmitted using about 75-100 milliwatts of power as opposed to the new beacons that are using 5 watts of power – a stronger transmission is a good thing in bad weather or storm conditions or when your location may be obstructed by things like cliffs!

New C-S System OverviewSatellites receiving the old analog 121.5Mhz and the new digital 406Mhz systems still use doplar shift techniques to try and resolve the location of the beacon. But the new system is accurate to about 5km (2.6nm) as opposed to the old 20km (10.8nm). The old analog system only transmits a tone so the SAR operation cannot determine what is going on until they locate the beacon and find out that it isn’t a false alarm or some errant piece of electronics like a set top box on TV! The new system transmits actual data digitally which can then be linked automatically to your registration data bringing up who to phone and details of your vessel and so on. In the UK you must register your 406Mhz beacon with the MCA

Is added GPS a useful feature?

If the unit you buy has the added facility to transmit GPS location data as well then the accuracy is even greater – about +/-125m. It isn’t as accurate as your chartplotter GPS simply GEOSAR Dec2008 smallbecause the transmission of the GPS data is limited by the message length of the protocol being used. Even if your beacon is destroyed in the emergency it only needs to transmit for a few minutes for the satellites to pick it up and resolve the location. Pretty damn good I think:-)

The main satellite system for picking the beacon’s signal is the SARSAT system, but in addition the geostationary GEOSAR satellites that cover more than 80% of the earths surface also pick up signals and can relay the GPS location data even though they cannot compute location themselves using the doplar effect.

So how do you choose a 406Mhx beacon for your boat?

The choice is then between Category I (auto deployment) and Category II (manual deployment) 406Mhz beacons…and also units with or without GPS.

I have prepared a small table of units available in the UK market below. Click on the images for a larger view.




Clearly I think you should get one with built in GPS, and if you can get a 16 channel GPS all the better. I dont think the CatI auto deployment is worth the extra money…


Code of Practice or Flag of Convenience?

I have long lamented the poor service that boaters whether power or BMEAsail get when installing electronics on their vessels. Getting someone that understands a good installation, is honest enough to read the manual before starting, and doesn’t rip you off with unexpected “extras” is as rare as getting a good plumber or an honest politician.

I have recently been looking at the The British Marine Electronics Association web site and noticed that they do more than represent the trade. The obviously are a trade organisations that represents installers and manufacturers of electrical and electronic equipment for marine use.

But they do have a “Code of Practice for Electrical and Electronic Installations in Small Craft”. This code is produced by the BMEA as a guide to how installations should meet the Standards required for compliance with the Recreational Craft Directive (RCD). It is based on the ISO Standards for AC & DC installations. The Code of Practice is available to all including trade and DIY installers alike and can be obtained through the BMF technical department (phone 01784 223634 or email: cabel@britishmarine.co.uk)

They also run an accreditation scheme called BMET. British Marine Electronics Technician accreditation is a new scheme that has been introduced to recognise the qualifications and experience of those involved with the installation of electronic and electrical equipment in boats.The scheme consists of intermediate and advanced level examinations and, verification of a candidate’s practical competence.

One can but hope that by choosing a company with staff that have attained BMET accreditation …”you can be confident that you will get the highest standards of workmanship and expertise …”

hmmm…is this like the logos that builders put on the back of their vans – or is it a real qualification?….I would love to know…


Which bilge pump?

Bilge pumps are like flares… you never need them until you REALLY need them, and when you do, you will wish you had 2 fitted!

The recent test of bilge pumps carried out by Profs. at Southampton Solent University for Practical Boat Owner has a few gems in it. I didn’t realise for instance that the recommended discharge point is at the stern just like the engine exhaust. The discharge pipe has to be as short as possible because the energy required to overcome friction can exceed the energy required to lift the water!.

Johnson 2200gphMost of the pumps tested were 12v, manual switched, and under £50. The most impressive were the Attwood Tsunami and the Vetus EBP 80 . Both capable of lifting 40 litres (10 gals) of water 1 metre in 1 minute, and a good flow rate for power consumed.

Due to lift height / friction loss in outlet hoses, bilge pumps are only running at (estimate) 80% of their stated capacity. So a 1200 gph bilge pump, is in the real world only giving you 960 gph.

A wave that swamps the cockpit can easily dump 500 litres (132 gals) of water in the boat in one hit. I realise that that does not mean that the water goes into the bilge -it should drain out of your cockpit drains. But, just imagine for arguments sake that the water all goes below. The Attwood Tsunami rated at 1200gph (4,542 lph) running at full capacity would take 6.6 minutes to pump this out. If you say that friction losses cause by the length of pipe reduce efficiency to 80% then the time to pump 500 litres would be more like 8 minutes.

Of course if the water was from wave then at least you have the inter wave delay to pump water out – if the water was coming from a leak in the hull then there would be no respite to the water ingress and the pump may be fighting a losing battle, Nevertheless it would, in theory, buy you a few extra minutes to find the right sized bung!

I think I would rather blow the budget of £50 and fit a higher capacity pump such as the Johnson 2200 gph pump.