GPS input to DSC VHF radio

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FairweatherDave

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The previous owner of my boat had a handheld Garmin unit outputting to the XM DSC VHF.
I am now setting up my AIS +GPS receiver (Quark A026) and realised maybe I can use that GPS output for the radio instead, but I wanted to check.

The Quark blurb says it has "NMEA 0813 input/output connectors. QK-A026 can be connected to other AIS compatible equipment , like wind/depth or heading sensors, via the NMEA inputs. The NMEA 0183 messages (4800kbps) from these devices can be multiplexed with QK A026 received messages and then sent out through WiFi,USB and NMEA outputs simultaneously.

My question is would that NMEA output be suitable for my VHF? (Elsewhere it says that NMEA output is 38400 bps).
The DSC radio is made (badged) by XM and was new in 2005, I have no other information about it at home.
Thanks for any answers, hope I can understand them.........


PS. My motivation for moving away from the handheld GPS as a source is that the connection is vulnerable to the elements up in the cockpit. The new GPS aerial for the AIS unit will be an internal one, a Universal 5.5mm SMA GPS Antenna like this

https://www.amazon.co.uk/gp/product/B008QV2ESG/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
Hope it works but a cheap enough experiment.
 
FairweatherDave said:
The previous owner of my boat had a handheld Garmin unit outputting to the XM DSC VHF.
I am now setting up my AIS +GPS receiver (Quark A026) and realised maybe I can use that GPS output for the radio instead, but I wanted to check.

The Quark blurb says it has "NMEA 0813 input/output connectors. QK-A026 can be connected to other AIS compatible equipment , like wind/depth or heading sensors, via the NMEA inputs. The NMEA 0183 messages (4800kbps) from these devices can be multiplexed with QK A026 received messages and then sent out through WiFi,USB and NMEA outputs simultaneously.

My question is would that NMEA output be suitable for my VHF? (Elsewhere it says that NMEA output is 38400 bps).
The DSC radio is made (badged) by XM and was new in 2005, I have no other information about it at home.
Thanks for any answers, hope I can understand them.........


PS. My motivation for moving away from the handheld GPS as a source is that the connection is vulnerable to the elements up in the cockpit. The new GPS aerial for the AIS unit will be an internal one, a Universal 5.5mm SMA GPS Antenna like this

https://www.amazon.co.uk/gp/product/B008QV2ESG/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
Hope it works but a cheap enough experiment.
Click to expand...

I do just that. It works for me. It's going to cost nothing virtually plus a very little time to try it. I think I needed the slow baud rate to get it to work.
 
FairweatherDave said:
My question is would that NMEA output be suitable for my VHF? (Elsewhere it says that NMEA output is 38400 bps).
The DSC radio is made (badged) by XM and was new in 2005, I have no other information about it at home.
Thanks for any answers, hope I can understand them.........
Click to expand...

You can try it, but you may find that your radio won't accept the NMEA data at 38400baud. Presumably you're feeding the AIS data in to a plotter - doesn't that have a GPS output you can use?
 
pvb said:
You can try it, but you may find that your radio won't accept the NMEA data at 38400baud. Presumably you're feeding the AIS data in to a plotter - doesn't that have a GPS output you can use?
Click to expand...

No. The AIS data is going via WiFi to a tablet....
But as long as I can't damage the radio by trying the NMEA data from the AIS receiver then it sounds like it is worth a go.
 
It won't damage the radio but I'd think it very unlikely that it will accept NMEA at 38400 baud, which is the only output option on the Quark (this is reasonable as it is primarily AIS data). Don't think there's a VHF that will take 38400 input.
 
Does the Quark have 1 or 2 NMEA Ports? I have just fitted a Digital Yacht AIS and it has two ports, both independently configurable. I have one port configured at 38400 baud going to the plotter and the other configured at 4800baud via a switch as a backup gps source to the radio. The primary source being the plotter.
 
MikeCC said:
It won't damage the radio but I'd think it very unlikely that it will accept NMEA at 38400 baud, which is the only output option on the Quark (this is reasonable as it is primarily AIS data). Don't think there's a VHF that will take 38400 input.
Click to expand...
Standard Horizon GX2000/2200 and their siblings do if configured that way
 
Reading the original post again, it talks about multiplexing other devices at 4800 baud through the Quark. It's unusual to have a port with different speed on its TX & RX. It sounds as though there may be two Ports. The slow speed port should have the GPS sentence on its tx.

Edit- ignore that just found the Quark A026 manual and it only has a single NMEA tx and rx
 
Last edited:
FairweatherDave said:
The previous owner of my boat had a handheld Garmin unit outputting to the XM DSC VHF.
I am now setting up my AIS +GPS receiver (Quark A026) and realised maybe I can use that GPS output for the radio instead, but I wanted to check.

The Quark blurb says it has "NMEA 0813 input/output connectors. QK-A026 can be connected to other AIS compatible equipment , like wind/depth or heading sensors, via the NMEA inputs. The NMEA 0183 messages (4800kbps) from these devices can be multiplexed with QK A026 received messages and then sent out through WiFi,USB and NMEA outputs simultaneously.

My question is would that NMEA output be suitable for my VHF? (Elsewhere it says that NMEA output is 38400 bps).
The DSC radio is made (badged) by XM and was new in 2005, I have no other information about it at home.
Thanks for any answers, hope I can understand them.........


PS. My motivation for moving away from the handheld GPS as a source is that the connection is vulnerable to the elements up in the cockpit. The new GPS aerial for the AIS unit will be an internal one, a Universal 5.5mm SMA GPS Antenna like this

https://www.amazon.co.uk/gp/product/B008QV2ESG/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
Hope it works but a cheap enough experiment.
Click to expand...

I feed my VHF its GPS data from my AIS transceiver. However, as said above, the AIS unit has to be set to 38,400 to output the AIS data so I feed it into a DY multiplexer (bought cheap on eBay) and use the 4,800 output for the VHF.

Richard
 
Well thanks for the further replies. I can't say I fully understand the 38400 to 4800 technicalities yet. More questions are likely to follow when I have had another play. I will google what a DY multiplexer is :),....

Hmmmm Any pointers on a DY multiplexer? A swift Googling did not yield results I understand.......
 
Last edited:
FairweatherDave said:
Well thanks for the further replies. I can't say I fully understand the 38400 to 4800 technicalities yet. More questions are likely to follow when I have had another play. I will google what a DY multiplexer is :),....

Hmmmm Any pointers on a DY multiplexer? A swift Googling did not yield results I understand.......
Click to expand...

Don't get too distracted with all this talk of multiplexers, it's an expensive solution. If your VHF can't accept the high-speed NMEA data (38400 baud), your cheapest solution is a standalone GPS receiver.
 
RichardS said:
I wouldn't have said that £50 was that expensive but different strokes, I guess. :)

Richard
Click to expand...

I found a second hand stand alone Garmin GPS35 hvs to do that job for about £15.00 - Wide power supply tolerance and the radio DSC function is totally independent of the rest of the boat network. It doesn't need to cost a fortune!
 
Well this is all interesting, I do understand the value of £50....or £87.46
As in my OP I do have access to my handheld so I'm unlikely to be shelling out for a multiplexer. But if the back up handheld and the handheld have both packed up then it is good to know the options. At the moment I want to get the AIS receiver doing its AIS thing first.....
 
For anyone like me who didn't know what a NMEA multiplexer is, I just nicked this off the Cactusnav website.....


Digital Yacht MUX100 Dual Channel NMEA Multiplexer

With modern AIS receivers and transponders outputting high speed NMEA0183 data at 38400 baud, it is often difficult to connect AIS data and low speed GPS or instrument data at 4800 baud to some chart plotters and/or PCs that have just one NMEA 0183 input. With the MUX100, all data received on the two input ports is multiplexed and transmitted on output 1 at 38400 baud. It Is pre-configured so that Input 1 accepts AIS data at 38400 baud and input 2 accepts GPS/instrument data at 4800 baud.

Often low speed GPS data is required to give position information to a DSC VHF, but when an AIS transponder is fitted the GPS data is often only available at 38400 baud which will be ignored by the VHF. The MUX100 intelligently takes the GPS data from the AIS present on input 1 and re-transmits this on output 2 at 4800 baud – which can then be connected to the VHF. As a safety feature, should GPS data on input 1 be invalid or lost, the MUX100 will automatically switch to the GPS data on input 2 and transmit this on output 1 and output 2. To avoid duplicated data confusing other equipment, the MUX100 automatically blocks duplicated data on Port 2.

Using intelligent priority switching, the MUX100 gives priority to input 1 but if GPS data is invalid or lost on input 1, it will automatically switch to input 2. When valid position data is received again on input 1, it will automatically revert.

Two LEDs on the face of the unit give indication of the data status, with a solid LED showing which port is currently providing GPS position and a flashing light on the other port to show that data is being received. If either LED is not lit of flashing it indicates no NMEA data present.

FEATURES

Dual input/output NMEA0183 multiplexer – simplifies NMEA integration and installation
Accepts 38400 baud data on input 1 and 4800 baud data on input 2
Combines all received data and transmits this data on output 1 at 38400 baud
Extracts the GPS data from the high speed input 1 and re-transmits at low speed on output 2
Important safety feature - gives priority to GPS on input 1 but switches to input 2 if position lost on input 1. Will switch back to input 1 when valid position fix data is received again
Easy to install IP54 black box solution
Opto isolated inputs and true NMEA differential output capable of driving several devices
 
I had a very similar problem. My existing GPS, which talks to my computer, running my charts, didn't "speak" to my new DSC radio as they used different versions of NMEA 0813. I bought a HH Garmin GPS just to get the position onto my radio. It's now my principal GPS as the display is so much better than that on my older Magellan.
 
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