Lowrance HDS-7 to VHF NMEA 2000

[chopperdog]

Have a 2007 Lowrance HDS-7, which has an unoccupied NMEA 2k slot.
I have purchased a Cobra VHF with GPS input.
Instructions are to come out of the GPS (Lowrance) with NMEA 2000 cable.
Connect to this NMEA cable with a red wire and black wire that attached to a plug that fits in the back of the VHF.
Sounds simple enough, but I do not know which cable to buy.

Do I need to buy the Lowrance NMEA starter kit?

I am assuming, possibly incorrectly, that I just need a cable.

Can I buy an NMEA cable with an open end, or can I cut the end off of an NMEA cable that has plug and connect to the black and red?

Thank you,
Rob

 

[jhebert]

Re: Lowrance HDS-7 to VHF NMEA 2000

Have a 2007 Lowrance HDS-7, which has an unoccupied NMEA 2k slot.
I have purchased a Cobra VHF with GPS input.

It is unlikely that the Cobra-brand VHF Marine Radio has a NMEA-2000 network port. If it does not, then you cannot connect the Cobra VHF Marine Band radio to the Lowrance HDS-7 chart plotter with a NMEA-2000 connection. You would have no need to buy a NMEA-2000 starter kit for this purpose.

I try to stay informed on the topic of VHF Marine Band radios with NMEA-2000 interfaces, and I do not recall any Cobra-brand radios having a NMEA-2000 interface. In looking at some Cobra literature about their radios, they seem very unclear about any sort of specification for the interface.

It is more likely the Cobra-brand radio has a NMEA-0183 LISTENER port. You can connect the HDS-7 chart plotter to that port by wiring an NMEA-0183 TALKER output from the chart plotter to the radio. This connection can be made by wiring the two ports together in some manner, choosing your own connectors or terminals. You just need to follow the guidelines for interface of NMEA-0183 devices. See

continuousWave: Whaler: Reference: NMEA-0183 Interconnection Guide

 

[chopperdog]

Re: Lowrance HDS-7 to VHF NMEA 2000

Yes, I just assumed that the instructions were referring to NMEA 2k.
All this is new to me.
Seems like it would be easier to get the GPS location to the VHF.
I have attached a photo of the Cobra instruction page.
Instructions refer to the Red connecting to the NMEA out positive, and the Black connecting to the NMEA out negative.
would i have access to these wires if using an NMEA-1083 interface?
I didn't see reference to these 2 colors.

Thank you very much,

 

[chopperdog]

Re: Lowrance HDS-7 to VHF NMEA 2000

Jherbert,

Great info sheet.
Thanks for writing it!

Would you please tell me if this sounds correct?
I could get a Lowrance NMEA 2000 cable, something like:

Lowrance NAC-FRD2FBL NMEA Network Adapter Cable

Then make a trip to radio shack to get pins, that fit in the cable, that could be soldered to the Cobra wires, or cut the end of the cable and use connectors.
Connect as follows:
Lowrance Yellow to Cobra Red.
Lowrace Blue to Cobra Black

Should work?

Just want to be safe with GPS in VHF offshore.

Thank you very much,

 

[jhebert]

Re: Lowrance HDS-7 to VHF NMEA 2000

On the Cobra radio, based on their instruction manual--I could not read that photograph of a page you posted--the NMEA 0183 interface (here I am assuming that is what is provided, as Cobra does not make this clear) the wiring is as follows:

If the input is a differential input then:
LISTENER A = RED
LISTENER B = BLACK

If the input is a single ended input then:
LISTENER A = RED
LISTENER B = (not provided)
GROUND = BLACK

You should verify with Cobra what sort of input they have provided. I don't see any information in their manuals that says what sort of interface is used. Is it differential or single-ended? Ask them.

ALSO VERY IMPORTANT: verify with Cobra what NMEA data the radio must receive, that is, what specific sentence must be sent via the NMEA protocol to the radio from the GPS. A typical sentence will be $GPRMC.

On a Lowrance HDS-7 you will not need any wiring related to NMEA-2000. The device should have a PWR/DATA cable. The NMEA-0183 signals will be on that cable.

I looked up some data about the HDS series at

http://www.lowrance.com/Root/Lowrance-Documents/US/HDS_INSTALL_IM_EN_988-10043-001_w.pdf

and found the HDS-7 is always in RS-422 (differential mode). That means the NMEA-0183 port wiring is as follows

HDS-7 in RS-422
TALKER A = YELLOW
TALKER B = BLUE

LISTENER A = ORANGE
LISTENER B = GREEN

Because the Cobra-brand radio has only half of the port--it is only a LISTENER--you will not be using the HDS-7 LISTENER port at all. You are going to wire as follows

HDS-7 TALKER to COBRA LISTENER

You will wire:
HDS-7 TALKER A to COBRA LISTENER A

If the interface on the Cobra is differential, then you will follow the guide and wire:
HDS-7 TALKER B to COBRA LISTENER B

but if the Cobra is not differential, then you will follow the guide and wire:

HDS-7 TALKER B to nothing, let it float
COBRA LISTENER B to HDS Chassis or GND or power negative

The safest approach is to assume the Cobra input is single-ended. Let TAKLER B from the HDS float. Connect the Cobra BLACK wire to the HDS chassis or GND or power negative. See if it works.

You should not connect the HDS TALKER B to ground in any configuration. If there is not a corresponding LISTENER B differential input, then let the TALKER B float.

To configure the HDS to send the correct sentences, see

http://continuouswave.com/whaler/reference/HDS_Menu.html#NMEA0183

A good place to start is with $GPGGA and $GPRMC

 

[Pez Vela]

Re: Lowrance HDS-7 to VHF NMEA 2000

If it were me, I'd go to Plan B and return the Cobra and then purchase a NMEA2000 capable VHF such as the Lowrance described here: Link-8 DSC/ VHF Marine Radio - LOWRANCE | Marine Electronics You would then set up an easy-to-do, modern day, Lowrance NMEA2000 cabling system capable of expansion into the new era of marine electronics.

 

[chopperdog]

Re: Lowrance HDS-7 to VHF NMEA 2000

It WORKS!
Thanks for all the input.

I hooked it up. On the back of the Lowrance is a double cable, labeled Power / NMEA 1083.
The NMEA cable ended in open (but covered) wires, right behind the control panel.
I connected the Yellow NMEA to the Red Cobra, and the Blue NMEA wire to the Cobra Black.
Success!

Thanks Jherbert!
I couldn't have done it without your assistance.
An additional benefit is that I had a chance to learn a little about my boats electrical system, and a little about NMEA 2k vs 1083.
A good Saturday project.

Have a great night,
Rob

 

[jhebert]

Re: Lowrance HDS-7 to VHF NMEA 2000

It WORKS!...Thanks Jherbert!

My last name is H?bert. Not Herbert. I am of French-Canadian ancestry.

You're welcome. Glad to help. NMEA-0183 is miserably supported by both the NMEA organization and many manufacturers (like Cobra). They must think boaters are more interested in becoming serial data interface experts than expert fishermen.

What sentence did you send to the Cobra from the Lowrance?

 

[Pez Vela]

Re: Lowrance HDS-7 to VHF NMEA 2000

I'm glad to hear Plan A worked out, with the indispensable expertise of Mr. H?bert. Congratulations to you both.