Using a Nextel GPS-enabled phone to feed an APRS tracker

It's simple to use your Nextel i58, i88, or other GPS-enabled phone for your tracker. All it takes is money, and a few key presses.

First, you will need the phone; as this is written, the only GPS-enabled (meaning "has GPS in it") phones being built by Motorola for Nextel are the i58sr and i88s. I went with the i88s, but the i58sr is "ruggedized"... i.e., it can take more of a beating.

Next item is a data cable. Motorola's "OEM" cable usually sells for $30, and has provision for adding power... albeit with an awkward 90 degree angle connection, 8" below the phone. There are after-market cables available for as little as $15, but not all can provide power... and the GPS draws a significant amount of juice from the battery.

That's it for hardware, at least to replace a GPS in a tracker such as the KPC-3 Plus or KPC-3 tracker, covered elsewhere on this site. Well, other than you will probably want a car charger to power the phone.

If, however, you have one of the Motorola "car kits", you will also need one of their data splitter cables. This fits between the phone and everything else, and provides ports to plug the data and car kit cables together. I haven't gotten mine yet... because the car kits are on back-order.

Setup is easy. You need to enable GPS output, by using [Menu], scroll to GPS, [SELCT], scroll down to Interface, [SELCT], [CHNGE], scroll to On, [SELCT], and back out of the menu. You must do this once for each time you power up the phone; the NMEA interface is turned OFF when the phone goes off. (apologies for poor pictures below; I didn't have the right lighting to do it right.)

Now, each time you plug the data cable into the phone, you will get a prompt saying the NMEA interface is on. Select the continue button, and GPS information will start to stream out to the tracker.

The new KA9VNV-1 has been using this for nearly a month. There has been the occasional glitch; for two days, I could not get the phone to output GPS information, even though it said it was ready to. I believe I've tracked this down to the interface cable itself, or, more specifically, what you plug it into.

If the cable is plugged into something that does no hardware handshacking (such as a tracker), no problems occur. However, if it is plugged into a computer, the phone will detect the hardware handshaking signals, and stop sending information when they go away. The only fix seems to be going back through the menu and forcing the NMEA output to ON... Even though it will still say it is on. Select [CHNGE], highlight On, and hit [SELCT]. This turns the output back on... until the next time you use the phone with a computer.

Always check for the GPS active icon when plugged in, because it tells you that you're feeding the tracker.


[Second draft (pictures added and explained), March 2003]
Copyright 2003 by Jeff Brenton KA9VNV
Last updated on: October 25 2013 19:14:01.