How to open Spektrum .TLM telemetry files

What a .TLM file is

A .TLM file is a binary telemetry log written by the transmitter. It stores the values that the telemetry receiver and the sensors in your model sent during the flight: radio link quality, signal strength, receiver voltage and, depending on your hardware, motor current, battery cells, height, climb rate, GPS position and more. Every time the receiver powers up, a new session starts in the file.

Get the files from an NX or iX transmitter

1. Switch the transmitter on and connect it to your computer with a USB cable.
2. In the transmitter's USB settings, choose the option to access the internal storage.
3. Open the drive that appears. Your logs are .TLM files named after the model, plus the AutoLog folder, where recent firmware writes a log automatically for each flight session.
4. Copy the files you want to your computer.

The transmitter tidies up its automatic logs. According to Spektrum's change log for NX, it keeps only the newest few files, so copy a log soon after a flight if you want to keep it.

Get the files from a DX transmitter

DX transmitters with telemetry logging store the logs on the SD card. Make sure logging is switched on in the transmitter's telemetry settings, fly, then take the card out and copy the .TLM files to your computer. The exact menu names depend on the model and the firmware version.

Open the files in TLMscope

1. Open TLMscope in any current browser.
2. Drop one or more .TLM files onto the page, or click to choose them.
3. Pick a session in the list. Each power-up of the receiver is one session; flights, ground tests and short power-ups are labelled.
4. Use the tabs for height, motor and energy, battery, radio link and the aircraft. Switch on “Show details” for exact values.

Large logs with many flights take a few seconds to read. Everything happens on your device, nothing is uploaded.

If a file does not open

• Check that it is a Spektrum file. EdgeTX, OpenTX and other radio systems write different log formats, which TLMscope does not read yet.
• Damaged files are read as far as possible: TLMscope skips broken records, shows a warning and keeps the rest.
• A session without a height sensor or GPS still opens; the views that need that data tell you what is missing.
• Files larger than 256 MB are refused. Real logs are a few MB.

Want to try it first?

Load the demo flight on the home page: a synthetic flight with GPS and a thermal that shows every view.

To find out what the numbers mean, read Understand your Spektrum telemetry. For the list of tested transmitters, see Supported transmitters and sensors.

Frequently asked questions