Connecting cheap GPS to DSC

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Slycat

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Hi all

I have a Cobra DSC which looks to have a GPS input along these lines:

https://www.cobra.com/products/marine/428-005

I'd like a cheap GPS option to meet the DSC GPS needs. There are a LOT of different basic GPS units on ebay etc but don't quite know which will output in the format the Cobra needs.

Anyone know of a model or how to identify one?

Many thanks!

Chris
 
I'm going to have a go at it myself sometime soon...

In protocol terms, it is probably safe to say that all GPS modules offered on eBay will be compatible with the input requirements of your radio. The situation in electrical terms is less clear - many of the cheap GPS breakout boards offered at £10 to £20 on eBay operate at 5v or even 3.3v and will, therefore, require a step-down power supply to drop the 12v rail of the boat. There may also be a question over their ability to output the NMEA signal at a high enough voltage to satisfy your radio - they are generally designed to link to other low voltage devices such as Arduino and Raspberry Pi single board computers and may not be able to drive an RS232 input port such as will be on your radio reliably.

I have a couple of cheap eBay GPS boards laying around and intend to try it out when I have time to spare. I shall initially try just hooking the output of the board to the input of the radio, but I will not be too surprised if it does not work. If that is the case, I'll insert a suitable level shifter - probably something based on a MAX232 chip.
 
I have a Garmin eTrex (like this one https://www.amazon.co.uk/Garmin-eTrex-GPS-Personal-Navigator/dp/B00003WGP5) connected to my DSC radio. It works really well, I find.

I have a lead that powers the GPS, and supplies the position to the radio. In the set up of the eTrex, you can select the output, so I just selected the one that the radio required as stated in the manual.

The little GPS unit can run on two AA batteries if necessary, and because they are old, they can be bought really cheaply. I keep the display on speed and direction , with the lat and long at the bottom which I plot on the chart. Useful as a back up log, compass, and clock, as well supplying a GPS position to your radio.
 
The Cobra will need NMEA0183 GPS data, which most receivers will supply. If you want a simple 12v plug-and-play solution, the Evermore SA-320 receiver is often suggested, at about £70.
 
pvb said:
The Cobra will need NMEA0183 GPS data, which most receivers will supply. If you want a simple 12v plug-and-play solution, the Evermore SA-320 receiver is often suggested, at about £70.
Click to expand...

And if you don't have a moderate amount of experience in hobby electronics, that is probably the best option. It is undoubtedly possible to make it work with a UBlox GPS module and a handful of other components available from eBay for less than £20, but there will be some assembly required and sufficient understanding of electronics to design and build a simple circuit which adds a power supply and, possibly, some level shifting to the module.
 
pvb said:
The Cobra will need NMEA0183 GPS data, which most receivers will supply. If you want a simple 12v plug-and-play solution, the Evermore SA-320 receiver is often suggested, at about £70.
Click to expand...
for that price youd probably be better buying an etrex or cheap garmin handheld.
 
ghostlymoron said:
for that price youd probably be better buying an etrex or cheap garmin handheld.
Click to expand...

Well, I'll have to take your word for it, but I didn't think the etrex could output NMEA data. As for a cheap Garmin handheld, they seem to go on eBay for around £45-£75, and you might need to buy a data lead in addition, and you'd still have an old secondhand unit with no warranty.
 
Most GPS pucks are NMEA 0830 as said but are alse USB. When I connected a GPS puck to my SH GX2000 the one I used was an older GPS with RS232 output at 4800 bps.

Make sure you get the correct type.

The RS232 GPS puck also needs a separate power supply. mine has a mini PC mouse plug for the 5Vdc that is needed where as USB incorporates the power and signal in one plug.
 
When I bought my current boat, the first thing I did was to replace the radio with a new Navman 7100, purely for the DSC functionality. I wired into the radio an old Garmin GPS60 I found in a locker, which powers from the radio's 12V supply. I don't recall the cost of the cable, but it wasn't expensive from eBay.
 
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