I am using my Samsung Galaxy SII (Japan Docomo version) for the development and test of U2APRS. As you know, there are many variants in the Android devices, each of which will have different characteristics and behaviors. Please do not be upset if U2APRS is not working properly on your device :)

U2APRS is freeware. The author of this software accepts no responsibility for damages resulting from the use of this product and makes no warranty or representation, either express or implied, including but not limited to, any implied warranty of merchantability or fitness for a particular purpose. This software is provided "AS IS", and you, its user, assume all risks when using it.

Version history

U2APRS version 0.65 or earlier is not compatible with U2APRS version 0.70 or later. If you have one of the older versions installed in your device, you must uninstall it first, and then install newer versions.

Tapping the version number gets the download started, but there is no install window poped up. What happens?

Try Chrome browser or Opera browser to view this page.

I have upgraded the Android version. The setup menu button of U2APRS disappeared. What happens?

U2APRS uses an old template. Long tapping the home button in the main window brings you the setup menu up.
Version Date Note
0.8.3b October 7, 2015 Changed the text color of the notification bar.
0.8.3a December 20, 2014 Changed the app development environment from Eclipse to Android Studio.
0.8.2i October 19, 2014 Changed the colors of the message packets and friend packets (TNX to JL1QXE).
Changed the pop-up location of notification of friends packet (TNX to JL1QXE).
0.8.2G August 8, 2014 Fixed minor glitches
0.8.2E April 6, 2014 Changed the colors of the satellite view.
0.8.2D March 6, 2014 Slightly changed the message display appearance.
0.8.2C November 29, 2013 Long tapping the home button (house image) calls the menu (TNX to JA7JEC).
0.8.2A September 14, 2013 Added an option that hides the aprs.fi tab (TNX to JL1QXE).
Added an option that clears cache data on application exit (TNX to JH7UJI).
The stations registered in the friends list show up in the main window.
0.8.1o July 5, 2013 Fixed GPS satellite view bug.
0.8.1M April 4, 2013 Fixed minor problems.
0.8.1L September 30, 2012 Added the mic gain slider to the AFSK decoder. Fixed minor bugs.
0.8.1E July 22, 2012 Change TTS routine for ICS.
0.8.1D July 21, 2012 Fixed minor bugs.
0.8.1C June 30, 2012 Fixed minor bugs.
0.8.1a June 2, 2012 Reconstructed U2APRS web pages

U2APRS, whatH

U2APRS is an APRS client application running on Google Android OS.

U2APRS is delivered only at this web site. It is not on the Android market.


Initial setup

Beacon setting

Friend sensor

Server setting

Other options

AFSK decoder


First of all, you should set the permission to your device to install applications that are not in the Android market.

Call Settings and tap Security.

Check Unknown sources.

Next, turn the Google location service and GPS on.

Download U2APRS.apk from this page. Click on the version number you want to install.

When the apk has been downloaded to your device, click on it to install.

Now, you have a U2APRS icon on the application desktop. The installation is completed.

Initial setup

Tap the icon. A small window is popped up and ask you to input your call sign and five-digit passcode. You might want to use a callsign with SSID, for example, JA7QRA-5.

Press OK to start U2APRS operations. U2APRS is automatically going to connect an APRS-IS server.

Beacon setup

The default APRS symbol used by U2APRS is telephone (/$).

You can change the symbol by tapping Station symbol. Select one of those listed here. You could define the two letter APRS symbol code at the top of the list if necessary.

If you want to display your position by the APRS symbol in the main window, check Use APRS symbol.

There are two ways to locate your position, that is, 3G/WiFi and GPS. Select Radio for 3G/WiFi or Gps.

Beacon interval (sec) defines the beacon transmission interval in the automatic beacon mode.

Traveling distance (m) defines the beacon distance. When you have traveled more than the distance defined here, U2APRS transmits a beacon.

Turn angle (deg) defines the direction change for beaconing. When your moving direction has changed more than the degree define here, U2APRS transmits a beacon. Putting 0 to this field disables this function.

Minimum beacon interval (sec) defines the shortest interval of beacons. The example below is 120 seconds, which means U2APRS will not transmit a beacon for at least 120 seconds even if you have traveled over the defined distance or your moving direction has changed more than the defined direction.

GPS on demand activates the GPS receiver in the Android device only after the defined time interval in order to save energy. When the interval timer expires, U2APRS turns the GPS on and waits for the location fix.

It should be noted, however, that this function does not work well on my Galaxy SII, which takes substantial time to get the GPS fixed. I no longer use this function on my Galaxy SII. It used to be working very well on my old Sony Ericsson device, which was able to get the GPS fixed very quickly. Thus, please use this function carefully.

Friend sensor

Friend sensor is "watching" APRS traffics on the APRS-IS network and notifies you of your friends' activities.

Tap friend list to edit friends' list.

Input callsigns you want to keep an eye out for. You could use the wild card "*" which matches any sequence of characters. JA7D* matches JA7DNO and JA7DNO-9 for example. Check boxes on the left hand side of the window enable and disable each entry.

Check the Sensor operation to start the operation. With Voice notice checked, U2APRS notifies you of the friend's activity by voice. With Vibrate checked, U2APRS vibrates the device when it detects the friend's activity.

At the same time, a toast notification appears in the center of the display.

When the Status bar notification is checked, an icon appears in the status bar at the top of the display.

Server setup

You can change the APRS-IS server address if you wish.

If Show server messages is checked, the messages from the server are shown in the Message tab.

Other options

Keep screen on disables the screen time-out lock.

If Run as service is checked, U2APRS runs in the service mode.

While U2APRS is running, you can start another application. U2APRS then continues running as a background job. However, U2APRS may be killed by OS when the memory resource falls short. This is quite normal in the Android OS. The OS is at first going to kill applications, then services, so that U2APRS in the service mode has greater chance to survive.

You must restart U2APRS to take this change effective.

When in the service mode, the titles in the tabs are preceded by *.


APRS is a registered trademark of APRS Software and Bob Bruninga, WB4APR. Thanks WB4APR for APRS. Thanks OH7LZB for aprs.fi.