connect DSC radio to a gps being used on PC using Opencpn nav software

[syjos]

To clarify:

I use a laptop to run my Nobeltec navigation software.

GPS data from a Furuno GP 32. Two wires to serial - USB to laptop.

Autopilot course data from laptop. Laptop to USB - serial two wires to Robertson AP 35.

The GPS and autopilot share the same Serial to USB adapter so the ground is shared.

AIS data from Standard Horizon GX2150. Two wires to serial - USB to laptop.

 

[sdowney717]

I have pretty much settled on buying the 12v gps with the 5 wires, simply dont believe the 5v one will work seeing the radio is 12v and I am not sure about sharing the grounds as in grounding the nema negative on the radio....

That is if I buy another gps just for the radio, i will still test my existing usb gps thru PC to radio. But I wont waste 10$ on a usb to rs422 converter when I can get a dedicated 12v gps for $17, to me that makes no sense.

I am a newbie at this for the moment, but I am a fast learner.

It will take a few weeks to get all these things figured out.

 

[STB]

Sounds like a plan!

 

[sdowney717]

Sounds like a plan!

I am pretty certain now it will work ok.
I notice they have a wiring diagram for a similar gps here, and it lists my Cobra radio. And it looks like wire info is very much the same, the thick black is ground for power, while the thin black is NMEA negative. Green is NMEA positive.

4800 baud is what marine vhf are looking for in gps data.
I can see why so many DSC capable radios are never hooked up to a gps, it is very confusing.
And on a PC, the strict rs232 protocols were not designed to work with NMEA rs422 but they sort of do work.

https://www.ebay.com/itm/GPS-RECEIV...2-VOLT-RS-232-SERIAL-CONNECTION-/222689774453

 

[STB]

sdowney717,

Yep! You've got it.

RS422, which what the present version of NMEA-0183 uses, was designed to be able to run wires over a longet distance and send the same data to multiple receivers. RS485 was designed to do the same and also allow multiple senders. The application for them were really industrial settings and embedded systems.

Home and office PCs just didn't need the ability to to either the distance to the peripherals is short and it usually one computer per each. So, there was little incentive for a more costly and less backwardly compatible serial port.

But, PC folks want speed. So, we got USB as a next gen serial port evolution of standards. I'll take it!

 

[sdowney717]

This DSC alert and calling is complex.
I found this procedure for our type boats,
Is it accurate in the USA?
https://assets.publishing.service.g...758898/GMDSS_DSC_VHF_Procedures_Nov._2018.pdf

And giving out the MMSI number verbally adds another number to remember.

 

[STB]

When communicating verbally, I think any identifier, e.g. name, call sign, or MMSI can be used. I'd probably relay the MMSI by reading it from the radio only if that is all I had.

USCG has various publications with instructions. One is here:

-- https://www.navcen.uscg.gov/?pageName=DSCDistress

The big win with DSC is that USCG gets identification and GOS location with one button press.

 

[sdowney717]

I opened up my 1970 Unimetrics vhf radio, and resetted 2 crystal boards
Its looks similar to very early model computers on the inside.

It is called a Seacom 55.

The inside of it looks really well made, they tied all the wires into bundles using a nice stitch cord.
And it works again.
So now I have 2 fixed radios, when I never really use radios. Wonder what to do with it, I will post a picture sometime today, I left it at the boat.
I did a Seatow radio check to channel 26 in Seaford, and my voice came back clear sounding. The only nice thing about that radio that lots of others dont have, it uses a handset with a switch that can direct sound to it or the units speaker. meaning no one has to hear whats being broadcast except you. It like an old land line telephone with a black handset. Its main detriment, its BIG, and heavy, it has a heavy aluminum case and again its big, and you can use channel 70 for voice, not allowed anymore.

found one on Ebay, so you can see what it looks like.
https://www.ebay.ca/itm/143318283182

 

[rgano]

s OP asked if after making a "private call" on DSC are you talking on a public channel? Yes. The "coded" call you make on DSC goes out on channel 70, but you NEVER talk on 70. Your call goes out as a hiss on 70 if you are listening and only rings the alert at the MMSI radio you are calling. The very best way to learn DSC is to get alongside another boat similarly equipped and try the various types of calling back and forth. If you are connected properly, the other boat can send you a POS message which will show upon your chart plotter/laptop/desktop. My brother and I once spent an afternoon playing with the four DSC radios we had on our two trawlers and found out that some radios (his Icomm in particular) did not play well with being called by a Uniden. We have cruised together at times, but rarely needed the DSC function because it was cumbersome requiring more buttons to push than we cared to mess with. We each had a channel 16 radio at hand plus another to chat on. If all else failed we had handhelds too.