DSC: Class D vs Class H?

[Cwens]

I note that Standard Horizon has replaced the HX-870, which was DSC Class D (among other things, a separate receiver always listening for DSC messages on Channel 70) with the HX-890, which is DSC class H (Among other things, it timeshares the receiver between Channel 70 and other channels.)


Should I, as the casual recreational sailor, care about the distinction? I think I understand the tradeoffs: lower power consumption and better battery life by not having a dedicated Channel 70 receiver, vs missing some (a little? a lot?) DSC traffic if the radio is busy on other channels.

[El Pinguino]

I found this to be of interest
https://continuouswave.com/forum/viewtopic.php?t=4428

[requiem]

Regarding the position polling, I have read that it was re-introduced with firmware update 1.12.

The unit I have here has the appropriate menu options to support it, and per the user manual: "The HX890 has the ability to automatically track seven vessels programmed into the individual directory, or to automatically send your position information to the programmed stations."

[capt jgw]

Has anyone here actually used DSC? I haven't, and couldn't care less if my radio had a dedicated or scanning ch70 receiver. I have my MMSI programmed in, but never called anyone with it nor had anyone call me. Commercial operators might use it all the time for company messages, but I doubt many pleasure craft do or even know how. The Mayday button is a different matter that makes it worthwhile to have DSC but that's got nothing to do with the original question.

[goboatingnow]

Class H was sponsored by the USA and was accepted by the ITU in 2019. The view ( from RTCM ) was that class D was not envisaged as suitable for hand helds as it was complex ( a view not shared by others )

The ITU standards for both class D and H don’t actually specify a dedicated “ watch receiver “ in either class. In Europe devices must both meet the ITU class D AND the relevant IEC technical standard which DOES mandate a separate watch receiver. In the US DSC radios do not need to abide by the IEC technical spec.

Ie ITU specs require reception of DSC alerts even if the receiver is being used to receive a voice call,but it does not , unlike IEC, specify a technical method of how to do that.

Hence class H handhelds MAY have reduced DSC functionality largely limited to sending distress alerts. ( class H , H for handheld , is only for handhelds )

But the radio must be capable of receiving ch70 messages , even if receiving a voice call.

It does this by rapidly multiplexing between the voice call and ch70 such that no ch70 traffic is lost thereby meeting the ITU primary requirement.

Ie from the standard horizon manual


The answer to your question is “no, you should not be worried “ other then a class H handheld “ may “ has less DSC features then a class D handheld ( in practice standard has put virtually all its class D features into the H model ) its functionally as capable as class D.

Note neither class D or class H are fully GMDSS compliant for GMDSS compulsory fit vessels. These must carry a class A unit.

[goboatingnow]

Originally Posted by capt jgw

Has anyone here actually used DSC? I haven't, and couldn't care less if my radio had a dedicated or scanning ch70 receiver. I have my MMSI programmed in, but never called anyone with it nor had anyone call me. Commercial operators might use it all the time for company messages, but I doubt many pleasure craft do or even know how. The Mayday button is a different matter that makes it worthwhile to have DSC but that's got nothing to do with the original question.

DSC is fantastic at sea because using ais you can get the ships MMSI and DSC them directly. I find “ ship at lat Lon “ calls are almost totally ignored these days , whereas if I DSC them I always get answered

Since the distress button is part of DSC you have to have DSC to get distress alerting

The issue is that DSC and GMDSS training is completely absent in the US due to lack of any operator training. DSC ( and GMDSS ) in Europe is far better understood as both are part of the CEPT training scheme for vhf operators license.


I also use DSC to contact my buddies in Greece and the coast guard radio stations ( when I was in Ireland )

[El Pinguino]

Originally Posted by capt jgw

Has anyone here actually used DSC? I haven't, and couldn't care less if my radio had a dedicated or scanning ch70 receiver. I have my MMSI programmed in, but never called anyone with it nor had anyone call me. Commercial operators might use it all the time for company messages, but I doubt many pleasure craft do or even know how. The Mayday button is a different matter that makes it worthwhile to have DSC but that's got nothing to do with the original question.

Nope, back in the day job we once had an 'almost local distress' come in on HF DSC- the rest of the time it was distress relays from the far side of the planet.
Back then and I suspect now any commercial traffic was done on Sat C.

VHF? also nope. Like you I bought mine - an 870 - for the distress function which is why I chose a handheld that can go in the grab bag.

[goboatingnow]

Distress relays are meant to be done using voice procedures only on MF HF. DSC should not be used to relay maydays.

Maybe it’s only me but I use DSC to call ships quite a bit especially in the English Channel.

[alctel]

I used DSC a lot when I was buddy boating. Saved cluttered up 16 constantly.

Also useful calling a certain boat on a crowded frequency as it sets off an alarm tone which is a lot easier to pick out rather than their name

[El Pinguino]

Originally Posted by goboatingnow

Distress relays are meant to be done using voice procedures only on MF HF. DSC should not be used to relay maydays.

Maybe it’s only me but I use DSC to call ships quite a bit especially in the English Channel.

Back in the early days of DSC distress relays were almost constant as the quickest ( only?) way to shut the damn thing up was to simply press the 'relay' button so you could get on with what you were doing ie berthing the ship or somesuch.
With a bit of luck new equipment has moved on a bit and now has a big red STFU button.

Note, I don't buddy boat or sail in the English Channel.

[El Pinguino]

Came across this on Panbo
https://panbo.com/standard-horizon-g...#comment-44549
'The Auto POS Polling function on the new Class H HX890 handheld is much different. The HX890 does not support the POS Request function. As a result, it cannot “poll” the fleet to elicit their positions.

Instead, it repeatedly transmits a POS Report (Safety Class) message to each of the “polled” stations reporting YOUR position to all of the other vessels, but not their positions to you. If their radios have not been configured to silence incoming POS Report messages (probably not a good idea for Safety messages), the radio of each of the polled stations rings off the hook until the message is acknowledged by the operator. A few minutes later, their radio is ringing off the hook again. And then again. And again.

In practice, the Auto POS Polling function on the HX890 should be called “Harass Your Fellow Boaters Mercilessly”.

Like GX2150, no transmitted messages are recorded in the TX Log. But unlike the GX2150, the HX890 receives nothing back from the polled vessels, so nothing is recorded in the RX Log either. In fact, except for an unobtrusive “A” icon on the display, it’s sometimes difficult to tell if the function is working or not.

Unless you’re in range to hear the howls of outrage emanating from your (former) “buddy boats”.'

[Uricanejack]

Originally Posted by El Pinguino

Back in the early days of DSC distress relays were almost constant as the quickest ( only?) way to shut the damn thing up was to simply press the 'relay' button so you could get on with what you were doing ie berthing the ship or somesuch.
With a bit of luck new equipment has moved on a bit and now has a big red STFU button.

Note, I don't buddy boat or sail in the English Channel.

Unfortunately STFU button still not standard on any set I’ve had the misfortune to use.
Not only no STFU button but they get worse if you try turning it off.

[requiem]

Originally Posted by capt jgw

Has anyone here actually used DSC?

Yep, mainly for buddy boating, particularly when they don't have AIS. The ability to "ring" someone up rather than being just background chatter is also convenient and skips the "switch to 6-8" routine.

[goboatingnow]

Originally Posted by El Pinguino

Back in the early days of DSC distress relays were almost constant as the quickest ( only?) way to shut the damn thing up was to simply press the 'relay' button so you could get on with what you were doing ie berthing the ship or somesuch.
With a bit of luck new equipment has moved on a bit and now has a big red STFU button.

Note, I don't buddy boat or sail in the English Channel.

No STFU button merely a ACK distress option

[hjohnson]

Originally Posted by goboatingnow

No STFU button merely a ACK distress option

I dunno, I find that momentarily keying the mic makes it shut up pretty quick.