Manuals, Timing, Ham Radio, Test Equipment

Help keep this site free:
(More Info)

Thunderbolt Monitor Android app

This app is designed to work with the Thunderbolt Monitor kit but will also work through the Lady Heather monitor software. The app has been tested on Android 5 through Android 10.

It is not a replacement for the full featured Lady Heather but it is sufficient to ensure that the Thunderbolt is running under nominal conditions. 

Main page

I wrote it mainly to help me check the WiFi option on the new kit but it has a few useful features:

  • Packet capture
  • Event Log
  • GPS Week Rollover correction
  • Send commands such as Self Survey or changing the time mode between GPS and UTC and other

The Packet Capture is only running when selected from the menu as it uses memory relatively fast. When enabled, the packet capture saves and stores the binary packets received from the Thunderbolt. The saved data can then be emailed or saved to a cloud storage account like Dropbox or Google Drive. The data can then be used for post processing on a desktop computer.

Event Log

The Event Log is always running but optionally displayed on screen by clicking on the View Log button. The Event Log saves an entry each time one of the main status indicators of the Thunderbolt changes, like Critical Error, Minor Error, GPS Status or Disciplining Status. Additionally, when "Track SVs in fix" is enabled through the Settings menu, the Log will record the number of satellites used in the fix and their SV number, which could be used to track poor performance that may be related to antenna location.

Note that leaving the main screen will immediately close and clear the Event and Capture logs so if you want to save this data, you must do it before leaving this screen.

However, as long as you are on the main screen and the app is connected to the Thunderbolt, the screen will not go to sleep so recording can continue. If the battery drops below 50%, the app will go to sleep if left unattended to preserve the battery.

Event Log

Capture Log

The Capture Log and Event Log can be saved to the app folder on the Android device itself or sent via email using the menu:


Satellites in View

Satellites In View (Used for Fix)

Send Command

The Send Command menu entry allows you to send certain pre-programmed commands to the Thunderbolt. At the moment, the list includes:

Commands like "Set Time to xxx" are not automatically saved to the Thunderbolt and therefore may revert to the previous setting when the Thunderbolt is reset or power recycled.

Note that if you click on a command, it will be sent immediately so be mindful of what you are asking for :)


The IP address (or URL) of the target device can be entered through the Settings menu.

Settings for a new host

The GPS Week offset is set to 1, which should be good until some time in 2038. The Thunderbolt Monitor kit will issue an alarm when the time to change this setting will get close.

The Debug mode is used to save additional information in the Log. It is a developmental feature so it may or may not be used in successive versions of the app.

You are not limited to monitoring a device on your home network. It can be used to monitor any Thunderbolt through the Lady Heather software. Refer to John Mile's Lady Heather page.

The app remembers the previous hosts so you can just click on one to select it, or do a long click to remove an entry from the list.

Most Recently Used Hosts

Click the Android Back arrow or in the IP Address box to close the list and enter information for a new host. As shown above, the IP Address box accepts a numeric address or a dns recognized host name and domain name.

The GPS Week Rollover issue is detailled in this page.

The User Guide points to this web page and requires an internet connection.

Public Access

Both John Miles (KE5FX) and myself offer on-line Thunderbolts at the URLs shown in the screen shot above so you can experiment. John's is connected through Lady Heather and accepts a certain (large?) number of simultaneous connections. Mine is connected through a TBMon kit and can only accept up to 3 simultaneous connections, so if it is busy, you will have to wait and try again later. Once you do connect, be nice with others and do not stay connected forever :) It is only intended to check that the app is working.

Active Mode

The app needs 3 packets to display all information it is designed for: The Primary Timing packet, the Secondary Timing packet and the Satellites in View packet. The Primary Timing packet is normally enabled by default in the Thunderbolt. The other two are optional. If your Thunderbolt is not configured to send these packets by default, simply select the Active Mode in the Settings page. When in Active mode, the app will send packet requests for these two packets at regular intervals.

When connecting to Lady Heather rather than the Thunderbolt Monitor Kit + WiFi, Active Mode should be selected in Settings otherwise Lady Heather will disconnect the socket after a few seconds even if the Thunderbolt is configured to send these packets. It is a feature of the Lady Heather network code so that a hung host will not clog the socket. These packet requests are sufficient to keep the socket open and the Supplemental Timing packet is necessary anyways for the app to display useful information.These commands are not normally necessary when using the Thunderbolt Monitor Kit + WiFi (as long as the Thunderbolt is configured to send these packets automatically). It does not hurt anything to select Active mode even if not necessary, it just causes a small amount of additional network traffic. On the other hand, if the network connection is dropped on the kit+WiFi without a clean disconnect, it may take up to 5 minutes before being able to access this socket again.


Finally, the app also has a handy Scanner utility that lets you check the IP address of your kit in case you have told the WiFi module to use DHCP.


The scanner will simply try to open a TCP connection to each IP address in sequence at the selected port number and report those ports that accept the connection. The port is closed immediately. There is no exchange of information.


The TBMon app is available from the Google Play Store, search for "TBMon" or click here.