GPS to VHF wiring for DSC?

snal · Posted: Wed Sep 05, 2007 7:39 pm Post subject: GPS to VHF wiring for DSC?

I kinda feel like I'm taking advantage of you guys and gals with all of my questions, but that's my best education, so bear with me Laughing

I got my new chartplotter in today, got it all wired up and the antenna mounted, works fine. My problem is connecting the GPS to the VHF for DSC operation. The GPS is a Garmin 172C and the radio is a Standard Horizon GX2340S (most likely a 1994 model) that I do not have the manual for. Garmin shows the white wire from the harness going to the VHF/DSC TX wire...and the green wire going to the VHF/DCS RX wire....my VHF has one wire with an RCA pin jack marked "DSC"... one wire with an RCA jack marked "NMEA", and one wire marked "SENS". Garmin support says I only need to connect the white wire (DSC TX) to the RCA jack to make this work...but that doesn't make any sense to me. Any thoughts?

rogerbum · Posted: Wed Sep 05, 2007 8:03 pm Post subject:

I assume that the signal is on the white wire and that since both units share a common ground that Garmin is correct and you only need connect the one wire.

snal · Posted: Wed Sep 05, 2007 8:09 pm Post subject:

But would this mean that I can transmit my DSC signal, but not receive one? Pardon my ignorance, but my understanding is that I should be able to receive a distress signal that may enable me to be of service?

gljjr · Posted: Wed Sep 05, 2007 9:09 pm Post subject:

That radio isn't on the Standard Horizon site. But here is a link for the Owners manuals they have on line. Maybe the GX2355s manual would help you out with the wiring (I'm assuming the 2355 is the replacement).

rogerbum · Posted: Wed Sep 05, 2007 9:18 pm Post subject:

That's somewhat dependent on both the radio and the GPS unit.

From http://continuouswave.com/ubb/Forum6/HTML/000726.html - "Not all VHF Marine Band radios have the ability to both send and receive DSC data. Typically, this feature is only offered on the more expensive models of DSC radios. Look for an indication that a particular radio has DSC position polling reception.

Also, not all chart plotters have the capability to display or plot the position of other vessels. Look for an indication that a particular chart plotter has an NMEA-0183 INPUT and will plot vessel position data it receives."

My guess is that you can transmit but not receive.

thataway · Posted: Wed Sep 05, 2007 9:31 pm Post subject:

I have two Standard Horizon radios (for practical purposes identical) but I can only recieve the position of the transmitting vessel on my Standard Horizon 175, and not on the Lowrance LCX 26.

Generally Standard has two wires for the input and two for the out put of the NMEA 0183 data. The ground circuit cannot not be always depended on to be the "-" of the NMEA data stream. Some of the manuals say that the out put will only work on the Standard Horizon chart plotters.

This is why it should all get better when everyone adopts NMEA 2000--but, it seems that RayMarine, still has "Sea Talk" and Furuno still has "Nav Net etc....so we are still not to a single standard. The reason is that the manufactures want to hook you into their entire product line.

The good news is that you will most likely not cause any damage by hooking up these wires. I would put a volt meter on first--and check to see that there are only millivolts and not 12 volts on the circuit.