Frequently asked questions

TLMscope is a free, browser-based viewer and analyzer for Spektrum .TLM telemetry logs. It runs on Windows, macOS, Linux, Android and iOS without installing anything, and the files stay on your device.

From a log it shows:

• a plain-language summary of each flight
• charts of height, climb, motor, battery and radio link
• a GPS map with 3D replay
• thermals
• battery ageing across flights

A .TLM file is the telemetry log a Spektrum transmitter saves while you fly. It holds what the receiver and the sensors in the model reported, for example signal strength, battery voltage, motor current, height and GPS position. See How to open Spektrum .TLM files.

1. Copy the .TLM file from your transmitter to your computer or phone.
2. Drop it onto the start page, or click to choose it.
3. TLMscope reads it in your browser and shows a summary of each flight.

No log at hand? Load the demo flight. The step-by-step guide shows where the files are on NX, iX and DX transmitters.

On its internal storage:

• logs named after the model, as .TLM files
• automatic logs for each session, in the AutoLog folder

Connect the transmitter by USB and choose the option to access the internal storage to copy them.

Yes. TLMscope is a web page, so it runs in a current browser on Windows, macOS, Linux, Android and iOS. Nothing needs to be installed. The map and the 3D replay use WebGL, which current browsers support.

No. Files are read in your browser and never leave your device.

Only for logs with GPS, the map loads map images from OpenFreeMap, which therefore sees roughly where you flew. See the privacy notice.

Yes, after one visit with internet:

1. Open TLMscope once with internet.
2. Wait until the footer says Works offline.
3. From then on it also opens without a connection, for example at the flying field.

On iPhone and iPad, add TLMscope to the home screen so Safari keeps it. Only the map in the Flight path tab needs internet.

TLMscope runs in the browser, so there is nothing to download from an app store. You can still add it like an app:

• Android (Chrome): open TLMscope, tap the menu ⋮ and choose Install app or Add to Home screen.
• iPhone and iPad (Safari): tap Share, then Add to Home Screen. This also keeps the offline copy, which Safari otherwise deletes after some days without use.
• Laptop with Chrome or Edge: click the install icon at the right end of the address bar.
• Mac with Safari: choose File → Add to Dock.
• Firefox: a bookmark is enough.

Then open TLMscope once with internet and wait until the footer says Works offline. After that it also opens without a connection; only the map needs internet.

Your log files are never uploaded or stored.

Logs from Spektrum NX and iX transmitters are tested. DX logs should work but are not tested yet. Radio link, motor, battery, height, GPS and more show up depending on the sensors your model carries. See Supported transmitters and sensors.

• Normal: Spektrum receiver manuals describe up to about 100 per minute in the air as normal.
• High quality: TLMscope rates up to about 20 per minute as high quality.
• Holds, about a second without signal, should not happen.

More in Understand your Spektrum telemetry.

A hold is about a second without any signal at the receiver. The receiver then applies its hold or failsafe setting. TLMscope always rates a hold during flight as critical.

A common rule of thumb is to retire a pack when its internal resistance reaches about 15 mΩ per cell. TLMscope estimates this value from the voltage sag in flight and follows it across flights for Spektrum Smart batteries.

TLMscope is free, needs no account and is an independent hobby project by a model flyer. It is not made or endorsed by Spektrum or Horizon Hobby. How it compares with other viewers is in Spektrum TLM viewers compared.

Yes. The main options:

• TLM Viewer: a long-standing, open-source Windows program with export to CSV and KML.
• TLMscope: free, runs in the browser on any device and explains each flight in plain words.
• Log Explorer: a paid desktop program that also reads other radio systems.

See Spektrum TLM viewers compared.