Lowest cost way of getting GPS feed into DSC VHF

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Alfie168

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My little boat is going from inland to sea shortly, so the brand new Navman 7100 VHF that has sat in its box for ages (oops) will been installed soon.

To use the DSC function I need a GPS aerial with NMEA output. The aerials seem to be more costly than the VHF!! Is there a more economical way of provided a GPS feed or am I stuck with my using it as a non DSC unit unless I spend about £100 notes?

I havn't got a plotter, just a basic Garmin etrex with no outputs of course.

Tim
 
Alfie168 said:
My little boat is going from inland to sea shortly, so the brand new Navman 7100 VHF that has sat in its box for ages (oops) will been installed soon.

To use the DSC function I need a GPS aerial with NMEA output. The aerials seem to be more costly than the VHF!! Is there a more economical way of provided a GPS feed or am I stuck with my using it as a non DSC unit unless I spend about £100 notes?

I havn't got a plotter, just a basic Garmin etrex with no outputs of course.

Tim
Click to expand...

mine is non dsc as well ;)
 
Try eBay and get a value gps aerial - or wonder why THEY want us to have these dsc radios anyway.
At some point, set free upon the briny, you will want a fixed GPS with an aerial so do it now.
 
How about using a GPS mouse?

You can also get them with USB connectors if that would help. But, I don't have (or want) a DSC VHF, so I have never tried connecting one to a radio. They work fine on my PC as a chartplotter & for active OS maps tho'.
 
Alfie168 said:
I saw those, but I don't think these have an NMEA output, well its not mentioned anyway, so i'm not 100% sure it would work.
Click to expand...

It wouldn't work! You're going to have to get a proper GPS receiver. If you're buying new, look for something like the Evermore SA320, for around £95. (Don't get the USB version). If you're buying secondhand, you could get one of the small Garmin sets for £40 or so, but you'd probably be better off in the long run getting a new unit.
 
Well, I've had a look at the manuals - and the usual fat lot of use they were, but as far as I can tell, the NMEA is an output option. The GPS connection will probably be SIRT3, which is what the GPS receivers above output. But what the connection socket provided is was not revealed in the manuals (WFT use is that then?) Have a look at your radio & see what standard the GPS input socket uses.
 
Alfie168 said:
I havn't got a plotter, just a basic Garmin etrex with no outputs of course.
Click to expand...

Are you sure you haven't got an NMEA interface on your eTrex? Does it have a rubber cover on the bottom that hides some large brass (coloured) contacts? If so, you will need an eTrex data cable (some come with a 12V 'cigar lighter' connection as well).

The data cable will provide the NMEA position sentence required by the radio.
 
Hi Tim,
I don,t know if your Garmin etrex will connect via nmea, I got myself a Garmin 72 on ebay and a data power cable for around £50 and works fine. Manuals are easily downloaded on tinternet. Hope this helps.
 
As far as I can see, the only advantage of linking DSC for you is that the lifeboat will arrive a bit quicker, maybe. I would be thinking about which bit of safety gear was the most important for me to spend my £100 on, and if my cruising were only coastal I don't think it would be a priority for me. A good lifejacket and up-to-date flares might be better.
 
johnalison said:
As far as I can see, the only advantage of linking DSC for you is that the lifeboat will arrive a bit quicker, maybe. I would be thinking about which bit of safety gear was the most important for me to spend my £100 on, and if my cruising were only coastal I don't think it would be a priority for me. A good lifejacket and up-to-date flares might be better.
Click to expand...

Thats rather my thoughts too, but if it were simple and low cost it would be sensible to use the safety features available so that one button press sends it all if it comes to that.

Searush, yes I'l have to check up the manual and harnesses provided. The manual seems to just mention nmea+ and nmea - as GPS conections.

Tim
 
The eTrex handbook, appendix F, shows the connections for a PC interface cable so it looks like it will output NMEA if selected in the interface options, and also power from the boat battery. Could not find a means of setting the NMEA data speed.
 
What a minefield!

pedantic mode on >

A GPS aerial or antenna doesn't output anything apart perhaps from a few microvolts of amplified radio frequency signal from some satellites.

Metaphor a vinyl LP on a turntable, the needles on the record. What comes out of the back of the needle is all but useless to the human ear.

A GPS receiver turns the signal into a sensible, useable format.

Back to our metaphor ... the pre-amp and main amplifier connected to the turntable.

Although its popularly called a GPS antenna in fact something like the Raymarine Raystar 125 is a combined antenna, to grab the signals, and a receiver to turn the signals into sensible data.

So you need a GPS receiver.

Now NMEA.

NMEA sentence data were originally intended to be delivered on a two wire serial interface . The spec actually says its a balanced signal line. ( NMEA + and NMEA - ). Confusion begins to creep in because PC users think that serial data signals out of the RS232 port are directly compatible with a NMEA port. They aren't, it works but electrically its all wrong and occasionally it just wont work with two particular pieces of equipment.

A USB GPS mouse ( antenna + receiver combination ) delivers its data, formatted according to the NMEA sentence configuration across a USB interface. USB is not a 2 wire serial balanced interface nor is it an RS232 serial port. It's something totally different and WILL NOT attach to any vhf radios currently available.

A metaphor may be a CD and our vinyl LP. The album on each is the same performance but the CD doesn't work at all on a turntable.

A garmin eTrex should have an output available and it's NMEA signal compatible. The cable connection plug is behind a rubber tab on the rear face of the unit at the bottom. If you buy a cable from Garmin it's likely to cost a few ready foldings, look for one on eBay. When you set the output to NMEA 0183 on the etrex the speed is fixed at 4800 baud ..... it's the standard.
This cable looks suitable and will allow you to connect to the ships battery to power the eTrex too

Pity. I threw away a box of about 5 big old 1st generation receivers a couple of weeks ago. Almost worthless these days.
 
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Hi Tim,

I had the same problem as you - needing to put GPS into my Icom radio to enable the DSC function. I had an old Garmin GPS 48 kicking about, and the power cable also has NMEA outputs. I had to configure the outputs using the setup menu and spend a bit of time trying to reconcile the Garmin and Icom wiring manuals, but got it all to work fine. I just have the GPS 48 on its bracket along side the Icom and it all works a treat, as well as providing a useful back up GPS unit. I am sure that if your etrex isn't suitable you will find a cheapo GPS unit on ebay..

Good luck

piers
 
I went own this route a year or so ago contacted a data cabling company (can't recall who) that did NMEA/Data cables to various handheld GPS units but alas, they didn't / couldn't do one for the Etrex... will have a dig and see if I can find them as they had a very usual website that explained a fair bit
 
Evermore SA 320

+1 for Evermore SA 320

http://cgi.ebay.co.uk/EVERMORE-SA-3...502886&cguid=74fe3b841260a0e2036661c6ff9c5000

Easily wired into any DSC radio.
Ours wired into the same power circuit as the radio so it is on whenever the radio is turned on. (it is very quick in aquiring satellites)

You also get the back up of an additional lat long display if your portable gps fails or you leave it at home!

In my case( Icom) I had to fit a coaxial plug from maplins to the appropriate wires which then plugged straight into the set.


Simples:)
 
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