Eschew obfuscation

[NOHOH]

I am trying to troubleshoot my electronics system.....and search as I might....I cannot find anywhere a simple, plain english answer to what I believe is a very simple question......

Namely......I have a Raymarine Raystar 125 Gps...

I want this to output NMEA directly to my DSC radio...... and nothing else......

My DSC radio has two wires going into it........nmea in+ and nmea in-

The Gps has 5 wires coming out of it.........red,yellow,brown, green, and shield.....

The gps manual says of the wires coming out of it

Red 12 volt + (obvious)
Yellow (nmea out +)......obviously connects to nmea+ in?
Brown (RTCM in/+) (whatever that is)(dont tell me...just tell me what to connect it to
Green (nmea in/+)........what does this connect to?
Shield (0V/ground/-)...what does this connect to....apart from the battery -ve?

Most importantly....what do I connect to the radio`s nmea in-..............I get the impression that Raymarine is deliberately obfuscating this when it ought to be completely straightforward...
Unambiguous Help please

 

[superheat6k]

My guess would be NMEA - on the VHF to the -VE / shield.

The green NMEA in on the Raymarine is for it to receive data from other devices.

 

[pvb]

The RS125 manual is quite clear. Connect the red wire to a 12v positive feed. Connect the yellow wire to the NMEA + input of your radio. Connect the brown, green and shield wires to the ground (12v negative) and to the NMEA - input of your radio.

 

[NOHOH]

Thankyou for that clear unambiguous explanation.............which I accept........but nowhere in the manual does it mention NMEA - I`ll give it a go tomorrow....

Again...many thanks

 

[pvb]

but nowhere in the manual does it mention NMEA

From the manual...

 

[NOHOH]

With all due respect.... I think you misread my last post....and mistook the minus sign after NMEA for a hyphen or a dash.......

(NMEA in/-) is not on the list in the GPS manual.......whereas the radio`s manual distinctly refers to NMEA (-)...not the power supplies negative......

Again... I think its just Raymarine attempting to obfuscate.......like labelling the output and input sentences GPGGA...etc.PRAYI etc.....rather than the commonly accepted `GGA`etc AYIetc

Anyway...thanks for your help

 

[laika]

(NMEA in/-) is not on the list in the GPS manual.......whereas the radio`s manual distinctly refers to NMEA (-)...not the power supplies negative......

Again... I think its just Raymarine attempting to obfuscate.......like labelling the output and input sentences GPGGA...etc.PRAYI etc.....rather than the commonly accepted `GGA`etc AYIetc

Your GPS follows an older NMEA standard. It is a "single ended" signal, that is whether data are 1s or 0s is measured by voltage relative to ground. The radio is designed according to a newer standard and expects a "differential" signal: Whether the line is transmitting a 1 or a 0 depends on the relative voltage between the NMEA + and NMEA - lines. The latter standard makes transmission more reliable over longer runs.

Fortunately for you this shouldn't really matter. If you connect ground/- on the GPS to NMEA IN - then the VHF will be looking at a relative signal between ground and NMEA +. It should just work.

As for naming, an nmea sentence is preceded by a talker ID. For a GPS this is normally "GP". Thus "GPGGA" *is* GGA with the (normal) GP talker id. "PRAY" would precede a proprietary raymaine sentence. I'm not familiar with a "standard" "AYI" sentence

EDIT: Quick look at the raystar manual shows that PRAYI is a proprietary sentence for configuring the GPS. That would be a sentence which you would send it (rather than one it outputs), presumably to configure it somehow (though no details given in the manual). Once again the "PRAY" denotes a P-ropritary (ie nonstandard) RAY-marine sentence

 

[NOHOH]

Anyway....... I seem to have made progress of a kind.......By eliminating the chartplotter, a multiplexer and an AIS....I managed to feed NMEA directly into the VHF radio (a Standard Horizon GX1500E)....and it still does not show time/ position data.... They had been talking to each other nicely for years......and suddenly stopped..so....it looks like the radios NMEA in/out port is the next item to be `looked at`

 

[laika]

I seem to have made progress of a kind.......By eliminating the chartplotter, a multiplexer and an AIS....I managed to feed NMEA directly into the VHF radio

Where did they fit into the picture then? To be a bit more unambiguous about the Raystar GPS to VHF...pvb wasn't making the mistake you thought was being made (although your confusion is understandable: most of us experience it the first time we encounter this situation). Connecting a device outputting single ended NMEA (ie one with only an nmea + out and ground rather than nmea + and nmea -) to one expecting differential input (ie nmea in + and nmea out -) your best bet is to connect the nmea out + to nmea in + and ground to nmea in -

 

[pvb]

Where did they fit into the picture then? To be a bit more unambiguous about the Raystar GPS to VHF...pvb wasn't making the mistake you thought was being made (although your confusion is understandable: most of us experience it the first time we encounter this situation). Connecting a device outputting single ended NMEA (ie one with only an nmea + out and ground rather than nmea + and nmea -) to one expecting differential input (ie nmea in + and nmea out -) your best bet is to connect the nmea out + to nmea in + and ground to nmea in -

How does that differ from my instruction?

 

[laika]

How does that differ from my instruction?

It doesn't. I was explicitly agreeing with you. I thought in post #6 NOHOH thought you'd made a mistake. I was saying you hadn't and expanded a bit to explain why you hadn't. Sorry if I misinterpreted post #6.