john_q
Well-Known Member
A very clear case you have put. My only comment is that I have an Icom 802 with DSC connected up but even in standby (receive only mode) it draws about 2 amps so I cannot afford to have the set on 24/7
What SSB do you have?
- Thread starter Oscarpop
- Start date
A very clear case you have put. My only comment is that I have an Icom 802 with DSC connected up but even in standby (receive only mode) it draws about 2 amps so I cannot afford to have the set on 24/7
blenkinsop
Well-Known Member
AllanR gives a good summary of the usefulness of SSB with DSC.
We had an 802 for our circumnavigation and it was one of our most useful bits of kit. I do not recall it using significant power in standby mode.
The only downside, if I recall the installation instructions correctly, is that to receive DSC alerts an extra antenna is needed.
We had an 802 for our circumnavigation and it was one of our most useful bits of kit. I do not recall it using significant power in standby mode.
The only downside, if I recall the installation instructions correctly, is that to receive DSC alerts an extra antenna is needed.
chuckr
Well-Known Member
i guess i should expand a bit -- we have an icom 802 with a at 140 turner and we use a GAM electronic antenna -- we did not want to cut our backstay and it works great -- all over the caribbean - mexico to colombia to jamicia to trinidad we were constantly told we had one of the strongest signals around
we did not install a ground plane but ran copper stripping along the bottom of the hull and attached it to the keel bolts
crossing the pond we were able to use winlink from quebec and halifax almost all the way across - and now in the med we use stations in swiz and austria
it works for us
we did not install a ground plane but ran copper stripping along the bottom of the hull and attached it to the keel bolts
crossing the pond we were able to use winlink from quebec and halifax almost all the way across - and now in the med we use stations in swiz and austria
it works for us
KellysEye
Well-Known Member
>Secondly, the satphone needs lots of money to operate. This becomes especially critical in an emergency, when the satphone can stop working because of a lack of credit or payment.
Emergency calls are free to a specific number.
Emergency calls are free to a specific number.
tri39
Well-Known Member
05.30Z Med Net on 8122kHz USB
06.00Z Dragnet on 6516kHz USB
08.00Z Uk Maritime net "Bill" on 14303kHz USB
Give these a call next season in the Med.
Spose there's a space for another one at 06.30Z !?
miyagimoon
Well-Known Member
Does the Med Net still run? I have never been able to pick it up.
What & Who is Dragnet?
Albert (MCZF6)
richardbayle
Well-Known Member
AllanR
New Member
Any existing antenna used for receiving only (NOT ANY TRANSMITTING) can be used for the Distress receiver function for an M801E and M802. For example, put a splitter in the antenna cable for the on-board FM/AM-radio/stereo and run one side to the DSC receiver input, with the other to the radio/stereo. It is not necessary to install another full HF/SSB antenna because this input to the radio is ONLY for receiving. Cmdr (US Navy ret) Terry Sparks - www.made-simplefor-cruisers.com , an experienced HAM and fixer of dodgy HF/SSB radio installations - also recommends a simple home-made antenna (made from stripped RG58 coax) hanging in a cupboard will be sufficient.
The idea of the seperate Distress receiver is that it operates constantly, always monitoring for DSC Distress alarms, even when you are using the main receiver/transmitter for a voice conversation or your SailMail or WinLink emails.
But, in terms of who you are in a position to assist, it's probably only vessels within a few hundred nm range, so having an antenna that will receive a DSC Distress alarm from vessels thousands of nm away is not realistic. If a distant MRCC sends a DSC alarm from their high-powered transmitters to request assistance for a vessel nearby to you, their signal will be strong and the smaller/simple antenna again sufficient.
AllanR
New Member
I understand that satphone calls to MRCCs around the UK/Europe could be free, but on this side of the world, I am not so confident. Please provide more information.
Nevertheless - on this side of the world - calling an MRCC for help with a satphone is not necessarily the proven recipie for a successful result when the MRCC lacks access to local area 24/7 standby, professional S&R services. For example see: http://www.sail-world.com/Cruising/...-to-find-shipwrecked-Australian-sailors/98741 and http://www.sail-world.com/Cruising/...-pay-hampers-search-for-missing-sailors/98618
Most MRCCs on this side of the world must enlist the services of nearby vessels to facilitate a response. This includes small-craft - yachts, fishing trawlers, coastal traders etc - that are not over 300 tonnes and therefore not required to have INMARSAT or similar satellite equipment so they can be tracked and called. There are many times more small-craft in the world than large commercial shipping, and most commercial small-craft operating offshore are required to have a DSC HF/SSB radio - eg: the ICOM M801(GMDSS) - on 24/7 standby. This creates a large network of moderately sized vessels which could assist a yacht. And to which a yacht could provide reciprical assistance, by also maintaining a 24/7 DSC watch.
We will not know which of these vessels are in the vacinity when we have a problem, and we will not know their satphone numbers. But a DSC distress alarm can be broadcast by the HF/SSB radio and will simultaneously and with one simple action, alert them all. They will all hear the voice responses and will be able to determine if they are in the best location and with the appropriate resources to assist.
Using a satphone for distress communciations on this site of the world - where MRCCs do not have RNLI resouces etc available - and in large ocean areas distant from coastal rescue services, seriously limits the ability to locate a nearby vessel for support, without making hundreds of calls; if you know the numbers.
A satphone call to an MRCC is not the simple answer. They still need to find a vessel in your vacinity and they need to get that vessel to commmunicate with you. The existing establishd maritime communicaitosn standard is the HF/SSB with DSC and the VHF with DSC. They may not have a satphone or may not have the credit - or authority from their boss - to use it.
And when it comes to managing the incident, all the HF/SSB or VHF radio communications between vessels lending assistance are free of charge, and they are broadcast, so everyone knows - simultaneously - what is happening and who is doing what. To achive the same inter-vessel communications via satphone will be very cumbersome, time consuming, sure to get details wrong/changed, and expensive.
These reasons are why MRCCs on this side of the world use and prefer HF/SSB radios. The relevent quote from MRCC Australia - with a very large S&R responsibnility area in the Pacific and Indian oceans - makes it clear: "While satellites and satellite-compatible distress beacons have significantly improved the effectiveness of S&R, the system is NOT a substitute for carrying appropriate marine or aviation radio. Depending on the circumstances, your initial distress alert should still be made by radio if possible. You should activate your distress beacon only if contact cannot be made by any other means, or when told do so by a rescue aurhority."
Why would they suggest the EPIRB should not be activated first; because the EPIRB has a limited battery life and it could take days to get a vessel to the location. Best to use the HF/SSB radio for as long as possible and only then switch on the EPIRB, eg when getting into the liferaft. Here is a recent example of a poorly equipped (for our side of the world) yacht in difficulty: http://www.mysailing.com.au/news/french-solo-yachtsman-rescued-off-tasmania-s-south-west-coast . No food or water in the liferaft, miniimal battery life for his VHF radio, and the ship diverted to assist took 50 hours to get there.
Yachts need to be more self-sufficient on this bigger, emptier side of the world. And have a HF/SSB radio with DSC as the principle form of medium to long distance communication. So they have quick access to prompt support from each other and nearby/local area commercial vessels for advice and assistance.
Neeves
Well-Known Member
ICOM M 800 with AT 120. Back Stay aerial and ground plate.
Now 23 years old and still going strong, needed to replace fibre optic cable twice and volume control once.
Not DSC enabled (before it was thought of?). Sufficiently parsimonious not to dump the existing equipment for DSC enabled.
In Oz and NZ we still have complete coverage of voice emergency channels, we can set up a voice reporting system with the same 'provider' across both NZ and Oz and there are a number of individual HF log on services. We need a separate Operators License for HF and a Station License (about Stg30/yr), though we have never been asked for either. I think we have given up on VHF Station Licenses but we are meant to have a licensed operator on board (but this is not strongly policed). Weather is given on a variety of 4 hour scheds covering all of Oz and surrounding oceans across a spectrum of HF frequencies and in the absence of VHF or Sat its the only sensible way to get marine weather here.
If you are straying outside Oz's major cities VHF rescue coverage is excellent (but not always 24 hours and drops off in our less populated parts of the coast, NW Oz, The Bight, west coast Tasmania) but HF is covered, as described above and we are, importantly still monitoring voice).
We would not be without it.
Jonathan
Now 23 years old and still going strong, needed to replace fibre optic cable twice and volume control once.
Not DSC enabled (before it was thought of?). Sufficiently parsimonious not to dump the existing equipment for DSC enabled.
In Oz and NZ we still have complete coverage of voice emergency channels, we can set up a voice reporting system with the same 'provider' across both NZ and Oz and there are a number of individual HF log on services. We need a separate Operators License for HF and a Station License (about Stg30/yr), though we have never been asked for either. I think we have given up on VHF Station Licenses but we are meant to have a licensed operator on board (but this is not strongly policed). Weather is given on a variety of 4 hour scheds covering all of Oz and surrounding oceans across a spectrum of HF frequencies and in the absence of VHF or Sat its the only sensible way to get marine weather here.
If you are straying outside Oz's major cities VHF rescue coverage is excellent (but not always 24 hours and drops off in our less populated parts of the coast, NW Oz, The Bight, west coast Tasmania) but HF is covered, as described above and we are, importantly still monitoring voice).
We would not be without it.
Jonathan
funk-an-bord.de
Active Member
I recomend a antenna with a flat = linear characteristic for DSC reception.
http://www.metzcommunication.com/weatherf.htm
When transmitting you tune the back stay antenna resistance to 50 Ohm for best power transmission.
But if you use e.g. a 5 meter long random wire for DSC reception,
you will get a antenna in resonance in the 20 meter HAM band = 15 MHz.
Then you will pick up the DSC at high frequencies 12 MHz (thats near to 15 MHz).
But the reception in lower DSC bands as 2,4,6 MHz will be poor.
The result is, that you get DSC alerts on 12 MHz. They are far away and of no importance for you.
So the alarm disturbs you.
And you will not be able to have a voice comunication with the station sending the DSC.
When you send a DSC call to a near by coast station on 2, 4 or 6 Mhz,
your watch receiver will not pick up the ACK
due to the reduced antenna gain of your DSC antenna on that bands.
So you can not use the DSC functions when you need in your neighborhood.
And where you would be able to get a voice comunication with the back stay.
A good way to test the DSC reception of your DSC antenna are the coast stations with automatic DSC test.
There is a new station in DOVER
http://www.gmdsstraining.co.uk/news-and-newsletter/
http://www.gmdssforum.net/index.php?topic=109.0
and Glenn Dunstan wrote that "the Australian and New Zealand stations offer automatic test calls."
I wrote that the US Coastguard is operating a DSC Testcall at 4 MHz.
If there are some more stations operating I would propose a new thread to this item.
Greetings Wilhelm
prv
Well-Known Member
Presumably it depends on the radio, but the commonly-used Icom models use the main receiver / antenna for the DSC routine watch. The separate DSC antenna is for distress alerts only.
Pete
funk-an-bord.de
Active Member
You are right:
You might use the DSC in routine calls and DSC function its working fine,
but without a apropriate DSC antenna you will miss the ACK on your Distress Alert.
For routine calls you have a two way radio with one tuned antenna.
You select the channel and when transmitting, the antenna gets tuned.
And the tuner will keep that settings during reception (in the general case of transmission and reception in the same band.
--
The watch receiver scanns the 2,4,6,8,12 and 16 MHz one after the other.
Therefore you need the additional antenna which can not be tuned to the frequency just received.
The gain of the antenna must be the same on all frequencies.
---
When you are sending out a DSC alert on all 6 frequencies you have
the concept of a two way comunication with two antennas.
When you have send DSC Alert on 2,4,6 MHz
and you are sending actually on 8 MHz your backstay is tuned for 8 MHz.
The coast station might send out an acknolewdge on 4 MHz,
but you will not receive the ACK when you have a 5 meter wire as DSC antenna
which is resonant at 14 MHz but has a poor gain on 4 MHz.
----
Not all coast station operate on all 6 bands.
Spanisch coast stations operate only on 8 and 12 MHz.
Thats another reason to look for a linear gain DSC antenna and to test it.
Wilhelm