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Splitting a GPS Signal

1st June 2003

 Article by Dave Burrows


I've been using a Garmin GPS Receiver for quite some time now (a GPSMap76S), and I've also been connecting it to a Compaq 3870 and find it's a great paired solution and works well.  One thing that struck me about 3 months ago, I tend to like to put GPS Receivers through their paces, and also Pocket PC's and cable sets.  Although as much as you try, you need to run comparison tests at the same time.  Seeing that the Road Angel is a GPS Receiver and also allows an output to a serial interface where you can plug in a Pocket PC and piggy back the NMEA stream, it then put my thought process into motion.


Wouldn't it be good if we could use one GPS Receiver and split the GPS signal to multiple PDA's ? 


I spoke at length with Ronald at PC-Mobile, and he agreed it should be possible.  Low and behold a couple of weeks later, I receive an email from Ronald saying he's manufactured the cables he's testing it and they work well with most PDA's!  I must say I'm really impressed.  PC-Mobile have now started selling these as the GDY2 cable.  Do you want to see why I'm so impressed with these cables ?  Take a look at what Ronald achieved!  This really is staggering!



Now unfortunately as much as I'd like to I don't have 8 Pocket PC's, but it really does go to show what you can attempt to do with GPS!  Basically the new GPS splitter cable allows you to connect two or more PDA's to a GPS Receiver.  Some PDA's due to their design cannot share the input data with one another.  The main Pocket PC that had issues was the Dell Axim, which strangely enough does have problems with GPS Receivers anyway, all the other tested above worked perfectly fine.


In my tests I managed to hook up three Pocket PC's, a Compaq iPAQ 3630, 3850 and 3870 all to a Garmin GPSMap76S and you'll see my test below.



I have also included a close-up of each of the Pocket PC screen, although they are difficult to read in bright light, you'll get the picture that I'm not trying to cheat you here!




This is of no use to me!

Actually it may be of use to you.  Most people when they upgrade to the latest Pocket PC tend to not sell their older Pocket PC and it starts gathering dust in the bottom draw.  If you were to purchase some splitter cables and connector's you could have two systems in-car, one on the drivers side, and one on the passenger side perhaps.  Or even one in the front, one in the back, or if you want to be really greedy, just have them both to yourself but run different applications on each taking the same GPS NMEA feed from a single GPS Receiver.




What cables would you need ?

First off you would need a cable to fit the GPS receiver, you can either go for the GRDC (Garmin Round plug), or GEDC (Garmin square plug), or the GMDC (Magellan plug).   See below.

Garmin Rounded Plug R-Type (GRDC)

Garmin Oblong Plug E-Type (GEDC)


This plug supports the following GPS Receivers:-


This plug supports the following GPS Receivers:-


Garmin GPS II

Garmin GPS III

Garmin GPS V

Garmin GPS 12

Garmin GPS 30

Garmin GPS 40

Garmin GPS 45

Garmin GPS 48

Garmin GPS 89

Garmin GPS 90

Garmin GPS76

Garmin GPSMAP76

Garmin GPSMAP76S

Street Pilot III


Garmin eTrex

Garmin eTrex Camo

Garmin eTrex Summit

Garmin eTrex Vista

Garmin eTrex Legend

Garmin eTrex Venture

Garmin Geko 201

Garmin eMap


PC-Mobile Magellan cable (GMDC)


Once you have the GPS cable, you can then look at purchasing your PDA cable.  You will need this as this will be what interfaces with your PDA.  Check out the PC-Mobile website and pick the correct interface cable.  For example, if you wanted to connect it to your Compaq iPAQ 3800, you would go with a GQ38 or a GQ36 for a Compaq iPAQ 3600.


PC-Mobile PDA data cable



Now you have the correct cables, what you'll need to do is purchase the splitter cables.  These are GDY2 and are available on the GDY2 PC-Mobile page. 


PC-Mobile GDY2 data cable


Each GDY2 cable will allow you to link up to 2 PDA's to your receiver, so 2xGDY2, each extra cable you add will add support for 1 extra PDA, so 2xGDY2's will support 3 PDA's and 3xGDY2's will support 4 PDA's.


If you would like some assistance on which cables to purchase, check out our Connecting a Handheld GPS Receiver to your PDA article as this shows you which GPS pages to look at on PC-Mobile and better explains how to connect the cables together.


If you are looking to use a Compaq iPAQ, then I would certainly suggest you look at using the GQ36P or GQ38P cables as these are powered versions and also off a Y split at the Pocket PC end allowing you to connect up a GPS Receiver but also to connect an in-car charger to charge and power the Pocket PC at the same time.


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