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Author Topic: HX-851: Can cheap Marine VHF sets do emerg work on 2m?  (Read 12775 times)

Posts: 160

« on: October 14, 2011, 12:51:59 AM »

So, we can pay ~ twice as much for a multiband VHF/UHF radio with GPS, APRS, etc.
...but do we really NEED to anymore?

Hams who sail would have seen Standard Horizon's HX-850 & its recent successor,
the HX-851.

In a nutshell it combines feature from several Ham handhelds:

+ VX-7R's waterproof (up to 30 min's in <= 1m of depth)
+ It has a very bright LED "strobe" that can send SOS, in Morse
+ The strobe comes on if it senses that it's floating [in water]

+ VX-8GR's inbuilt 12-ch GPS & knows how to send your location "bread-crumbs"
+ It can ALSO receive others' digital "bread-crumbs" & lead you to one of them

+ 6-watt VHF transmitter like some older ICOM gear, etc.

+ reasonable battery-life (if not quite as long as HX-400's or, in AU, ICOM's IC41S,
   which is a UHF-CB radio)

+ It's easy-to-use, not unlike some other single-band Ham handhelds
+ It's priced near enough to other Japanese single-band Ham h'helds

NOTE: Some of the above features may be new to HX-851's,
as you'll see on this clip - on HX-851E - by Jake Kavanagh:


I guess the HX-851 is "cheap" because its maker anticipates that it
will sell in greater numbers than, eg, the multiband VX-8GR, which
is fair enough...

BUT is there ANY way Hams could Mod an HX-850 or HX-851 to 2m?

If so, could we Hams "import" the well-defined DSC standard (by
which all those GPS-based "bread-crumbs" are exchanged, now,
over Marine VHF channels), & give new Hams all that functionality
in a low-cost, single-band radio?

Having an HX-850/-851 converted to 2m would sure make land-based
positioning cheap & easy, ie, if there are no hitches to doing so.

Has anyone tried? ...or worked through the trade-off's that might
arise in trying? ...are there any technical or regulatory hurdles
to jump over here?

Yaesu might like to consider offering a similar radio to Hams, &
save us all the time pondering such questions, but - until they
do - what do you think? ;-)

Can we do it? If not, why not? If not now, when & how? ;-)

Has anyone done any first-look experiments or test?

I'd appreciate any feedback or results on the possibilities.


Chuck Vk5CQ, etc.

"Ham Radio Advocate"

Posts: 376

« Reply #1 on: October 14, 2011, 11:38:00 AM »

This is maybe more a question for the modification forum, but I just wanted to note a couple of things:

As far as I know, DSC isn't a replacement for APRS - it's not meant for constant beaconing positions or passing messages like APRS; it's meant to set up voice calls, to call stations to listen to a specific frequency. (For HF/MF, you can set up CW and data mode contacts with DSC too.) It also supports setting up phone patch calls automatically through coast stations. It allows you to send your position, or to inquire for a position, but it's more an aid to rescue work than a beacon system.

In the marine environment, it's AIS transponders which are used to constantly beacon positions. and other sites also show AIS info for ships.

If you want to completely transfer a marine VHF DSC that to amateur use, you would need to decide which channel to use for DSC signaling, you would need to listen to that frequency before sending out a DSC, and you would need to reach a consensus for how to channelize the FM simplex part of the 2 meter amateur band. You would also need to modify the mode somehow to send your amateur ID, and you would need to find some way to translate the MSI number into something which makes sense for amateur. You would probably also need to change its physical appearance, so it doesn't get mistaken for a functional emergency radio.

If there's a way to open the HX-851 up for amateur radio frequencies, that would be nice, but if that meant having to take it off marine VHF frequencies, or mess up the DSC, I wouldn't do it. If you're on the sea, having a marine VHF radio which can call other people on the ocean, send out a distress call with the push of a button, and set up phone calls, is a lot more useful for emergency use than a pure single-band amateur radio that looks like a marine radio.

A VHF marine radio is already a good emergency radio. If you want to modify something for emergencies, you could modify your amateur HT to transmit on channel 16 in emergencies, but remember that it's highly illegal to use that frequency on your amateur HT unless you're saving lives.

A marine MF/HF radio like the Icom M802 with DSC is easy to open up for amateur use, and it's a good idea to do it.

We already have a form of selective calling on VHF/UHF amateur radios, such as the VX-8R, but it requires the radio to be set to - or scanning - the calling frequency, and then you need to QSY after talking about what frequency to go to. Maybe the concept of including a suggested traffic frequency, could be carried over? For HF, amateur radio already has something called Automatic Link Establishment: Like in marine DSC, the radios in HFLink scan digital calling frequencies for digital calls.
« Last Edit: October 14, 2011, 11:54:21 AM by LA9XSA » Logged

Posts: 160

« Reply #2 on: November 02, 2011, 10:31:08 AM »

Thanks for your excellent, comprehensive reply.

I agree that a handheld wouldn't be the radio to modify (unless a simple freq change could do it); the fact that these (as well as other GPS-equipped configurations of DSC radios) can be polled for their locations might preclude the need for any changes to band plans, etc.

Someday, agreement on a national 2m DSC frequency might be enough (ie, if / when the numbers warranted it).

Its ability to relay weak, local signals seems to make APRS a superior technology, but the cost of radios with GPS + TNC built-in makes them less likely to be available where / when needed, at the moment.

(A Finnish ARC had a APRS beaconing kit, built around a single-band Chinese handheld. All-up the beaconing radio (with an external [OEM] GPS & custom [Tx-only?] TNC, all cables) cost about $250... just add an antenna & 12v DC to start sending, if at only 5 watts. I guess that could be modified to give back access to the handheld's voice functionality, in a pinch.)

I'd really prefer our Amateur Radio gear makers go the way of smartphones, ie, including GPS [+ Amateur-specific APRS] functionality by default, but D-STAR adds another [proprietary] incompatible (with APRS) standard to contend with, essentially fragmenting the Amateur digital community into at least 2 camps & making it harder to justify "include GPS, etc. by default" thinking in Ham gear, any time soon.

Meanwhile, I guess Hams can always do what we've always done to reduce prices: Get some surplus ex-commercial radio(s), make the freq mod's, add a TNC (like the Finnish club added a new, COTS (here, the C could also stand for Chinese ;-) handheld radio, & DIY.

In an emergency, it's just nicer to have some low-cost, COTS solutions to choose, if only so that operators would find it easier to set them up correctly, eg, when sending them out with, eg, non-Ham search teams, etc.

It must be deemed a big problem, otherwise, the ICOM / Kenwood / Yaesu's of this world would have offered cheaper, "incl's APRS + GPS by default" radios by now... :-)

Posts: 376

« Reply #3 on: November 02, 2011, 04:06:52 PM »

There are some amateur handhelds with built-in GPS, like the VX-8GR and Kenwood TH-D72A, but the market is much smaller than for cell phones or marine DSC radios. I think it's a simple question of supply, demand, and economies of scale.

There's not really any reason why a D-STAR radio can't have APRS as well - ICom could do it if they wanted. A further problem with D-STAR position reporting is that it's not standard, and it's only ICom radios that necessarily uses the data segment of D-STAR for GPS data. (For the time being, it's only ICom and a few individuals which make D-STAR radios at all, which might change if the Codec2 project reaches success.)

As for modifying commercial land-mobile radios for amateur use, that's done quite often. It'll be interesting to see if there will be much amateur use of commercial digital modes - there's already quite a few P25 enthusiasts if you look in the amateur digital voice forums.
« Last Edit: November 02, 2011, 04:13:40 PM by LA9XSA » Logged
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