OCC Forums

Boat-to-boat DSC Calling - Individual & Group


By Allanr529 - 9 Mar 2016

Here is some information that I hope is useful for members crossing oceans or exploring island chains and coastlines.

There are very distinct advantages of using the DSC capability of ICOM 's M802(DSC) and M801(E/A) radios for boat-to-boat calling for General communications. But to get it working requires amendments to the default radio setup.

The default setup assumes that - apart from comms on 2 Meg MF frequencies - all communication from small-craft will be with coast stations. Therefore, the default DSC calling setup on the 4, 6, 8, 12 and 16 Meg DSC General calling channels is duplex, and cannot possibly work for boat-to-boat calling.

The reality is - according to my contacts in the GMDSS/IMO world - there are no government run coast stations anywhere in the world monitoring for DSC calls on these General calling frequencies. Government run HF/SSB coast stations only provide a listening service on the DSC Distress calling frequencies, which are simplex; so Distress calls can reach other nearby vessels, as well as distant coast stations.

But boat-to-boat DSC calling using the General receiver/transmitter in these radios creates significant day-to-day operational benefits for crews because these radios can be left on 24/7 in a speaker muted quiet mode, with the radio (not the crew) doing the work of listening for DSC calls - General (Individual or Group) and Distress (All call).

Three distinct advantages arise by maintaining HF/SSB radios in a 24/7 DSC watch:

1. Groups of yachts travelling together can provide quick response 24/7 mutual support for each other. Without needing to wait for the next voice sked.

2. Groups of yachts can immediate contact either another specific yacht (by sending a DSC Individual call to that yacht 's MMSI), or the entire group (by sending a DSC Group Call) to get advice about a dinner menu, anchorage, technical problem etc.

3. Yachts become immediately accessible S&R resources for any other mariners to contact via a DSC Distress call. This also applies to MRCCs making a DSC Distress call to find a nearby vessel to go to the site of an activated EPIRP or PLB.

To get these benefits from your M802(DSC) or M801(E/A) requires some straightforward changes that are detailed in the two attached documents.

Also attached is a document with a report from the skipper on a yacht participating in the ARC/WCC rally group crossing the Indian Ocean in 2015 regarding the process of getting the group to make effective use of their DSC capable HF/SSB radios to create a 24/7 mutual support network by first, making the necessary amendments, and second, utilising their Group Call ID to give all the crews the ability to send one DSC call to alert all the other radios in the group, simultaneously, to then make voice contact.

I hope this is useful. Any comments or questions, I 'll try to respond. Or email me at radio@bruneibay.net

Best wishes

Allan Riches
OCC Port Officer - Brunei
By dcaukill - 10 Mar 2016

Thanks for posting the mechanics.

What is your experience of leaving your Icom on standby in power consumption terms?

We kept a DSC watch in the last half of our circumnavigation but it proved to be such a drag on power reserves for some boats that we eventually agreed DSC listening watch periods morning and evening.

I don 't have the data here but my recollection is that on DSC watch, the draw was said to be a little less than half a kilowatthour.
By Allanr529 - 10 Mar 2016

Looking at the previously attached report from Peter, he advises that a yacht in their group tested consumption in DSC watch as less than 2 amps. Hence the comparison that running the radio requires less power than electric refrigeration or a few lights.

My understanding is it also depends on the radio. I 've been told by people more technically competent than I that the ICOM M802(DSC) is about 2 amps and the ICOM M801(E/A)is a little more, about 2.5 amps. Despite the M802(DSC) running a fan to pull dust and salt air through the radio for cooing purposes, the M801(E/A) - without fans but with a fully enclosed aluminium body that acts as a heat sink to dissipate the heat - draws more power in DSC watch because it has a more sophisticated power supply. This power supply can create 13.8 volts from lesser battery voltage so the radio can maintain transmit power despite the batteries losing voltage.

I understand this voltage stabilization ability of the power supply and the salt water, salt air and coffee proof sealed casing are why some communications authorities around the world require the M801(E/A) and will not approve the M802(DSC) for recreational vessels.

Apparently, the M802(DSC) was developed at the request of the USA fishing fleet for a lower-cost HF/SSB with DSC radio, based on the assumption they always have a generator running for constant voltage.

Hope this is useful.

By bbalme - 11 Mar 2016

This is all excellent information! I will be organizing the Southern new England Cruise this summer and will attempt to get everyone to program their radios for 24/7DSC operation - why not?!

It 'll be great practice for the Patagonian rally (if we manage to get that off the ground).
By Allanr529 - 12 Mar 2016

Hi Bill,

I 'm very pleased this looks useful for the OCC events.

Returning to the topic of power consumption, another OCC member contacted me direct and advised their M801(E) draws 3 amps, which for them is a lot to sustain 24/7.

Perhaps I can provide this information for members ' benefit:

1. Simon Boyde is based in Hong Kong and has been instrumental in development of the Special Regulations for Royal Hong Kong Yacht Club 's RORC race events ( eg: China Sea Race, Hainan to Vietnam Race). These now require a DSC capable HF/SSB radio for all events beyond coastal VHF (with DSC) range. And they require that the HF/SSB radio is always on, in DSC watch mode, with the MMSI IDs of all other yachts in the race entered in the radio, as well as the race Group Call ID. If you don 't have the radio or cannot maintain 24/7 watch, you cannot enter the events.

2. Simon owns a yacht and participates in RHKYC events. His own yacht has a ICOM M801(E/A).

3. He 's certainly been asked by numerous yacht owners - forced to install and maintain a 24/7 DSC watch on their DSC capable HF/SSB radio for RHKYC events - about the power demand. He has advised me that - through correct testing procedure - he has determined the power requirement for his ICOM M801(E/A) is 1.9 amps. Simon suggests a small solar panel will provide most of this requirement.

This is a similar power requirement independently reported by a member of the Indian Ocean rally group who had the knowledge & equipment to do an accurate check; less than 2 amps. So perhaps the power requirement is not so great as we have feared.

Peter (SY Exody) in his report advised to add the HF/SSB radio 's power requirement into a yacht 's overall power planning strategy. Because running the radios 24/7 was perceived by those rally participants to have mutual support advantages that made this worthwhile.

I hope this is useful.



PS: LATE ADDITION: Simon (RHKYC) also says it is important to turn down the radio 's speaker volume when in (speaker silent) DSC watch mode, as this does significantly lower power consumption.
By nicholas@dwyer.ie - 29 Mar 2016

Ignore this post :( B)
By nicholas@dwyer.ie - 29 Mar 2016

This seems like a neat innovation /application of DSC. I look forward to hear of wider sea trials.

By Allanr529 - 30 Mar 2016

Hi Nick,

I agree, it would be great to get feedback from OCC members trying DSC Group Calling with their VHF and HF/SSB radios.

In terms of other sea trials, I can advise that locally here we have a dive operator using a unique DSC Group ID for his operation, and their radios also have the NAVAREA Group ID entered. Therefore he can easily send/receive DSC group calls with his dive operation boats and his shore base. Contact with the boats is far more reliable, despite engine noise and the temptation to turn down the speaker volume. His radios are also listening for a NAVAREA XI Group DSC call from any visiting yachts etc. Using VHF marine radios with DSC

Once the yacht club here has their antenna tower up, they will be doing something similar, all the club members boats and base able to send/receive DSC Group Calls using the club 's unique Group Call ID. And also listing for NAVAREA XI Group calls from visiting yachts. Also on VHF marine radios with DSC.

I think the experience of the WCC/ARC rally group crossing the Indian Ocean in 2015 was a useful sea trial. (Document included with an early post)

Royal Hong Yacht Club has compulsory use of DSC capable HF/SSB radios in their events - including RORC events - since the start of 2015; when the event goes beyond coastal VHF (with DSC)range. They have an assigned club Group Call ID which all the yachts are required to enter into their radios prior to participating in events. They have now also distributed information on our NAVAREA based Worldwide Group Call Network to members and to participants in the recent China Sea Race. OCC members might be interested to read the attached documents from RHKYC (approved for distribution) related to this.

What also might be of interest to members are Simon 's comments about satphones at the end of the attached RHKYC- DSCRadioRequiremetns document.

Apart from being a yacht owner and a volunteer comms officer for RHKYC, Simon runs a business selling radios and satellite based systems to yachts, fishing trawlers, superyachts, commercial vessels, tugs etc. He gets a lot of feedback, and complaints when things don 't work. Therefore - despite the fact he could make a lot of money on the sale and call time recharges for satphones and satellite based equipment - he says first get a HF/SSB radio, and only consider certain satellite based systems; those he 's found generate minimal customer complaints.

Simon 's comment in the attached document regarding his experience with the lifespan of a satphone in a lifraft is also illuminating.

I hope OCC members can also try this system and give their comments.


By MikeReynolds - 20 Apr 2016

Thanks to Allan (also Terry Sparks and Bob Smith) for establishing the NavArea DSC Group IDs which will certainly enhance routine DSC calling.

Configuring Icom M802 / M802E transceivers for routine calling is a non-trivial task. Terry 's book provides instructions. My post at http://yachtzenagain.blogspot.com/2015/06/hfssb-dsc-routine-calling-with-icom.html also gives step by step instructions. With this done programming Individual and Group IDs is simple.

Configuration varies depending on whether the second (DSC Receiver) antenna is connected to the unit. If so then all DSC Watch scan frequencies can be changed to routine frequencies. If not then I recommend 3 routine and 3 emergency frequencies.

Likewise, learning how to make DSC calls and how to receive DSC calls isn 't entirely obvious. It is very, very easy to hit the wrong button. This is something to practice before starting cruises which will use DSC!!!

Hope the above is useful to someone!
By Allanr529 - 29 Apr 2016

Hi Mike,

Thanks for the very useful inputs.

In the UK, people have the significant advantage of RYA DSC radio courses and I certainly suggest this is very worthwhile training for long or short trips; basically anywhere beyond coastal VHF range and therefore where a HF/SSB marine radio with DSC and maintaining a 24/7 link (via VHF and HF/SSB radios) between yachts using group calls becomes relevant and important to create a mutual support network for general info and advice, as well as a quick response from nearby boats in the unlikely case of more serious problems.

Bob Smith at Yachtcom - www.yachtcom.co.uk - has been part of our team to establish the Worldwide Group Call Network and has lots of experience conducting radio training and with radio installations.

Having a copy on-board of Terry 's comprehensive book on the M802 (almost identical operation with the M801) is also strongly recommended as a ready reference. Vastly more useful than the manufacturer 's very basic manual. This book helped the WCC/ARC rally group in the Indian Ocean in 2015 get their radios functional and their 24/7 group call system working. Contact Terry at http://www.made-simplefor-cruisers.com/ to get a book. Or Bob may have some available in the UK.

My apologies for the commercial plug for these two people, but experience over this side - with far less land based S&R resources and support, and much lower shipping densities - shows that an effective radio linking yachts in a reliable 24/7 network can really make a big difference.