# Tether Diagnostics extension documentation **URL:** \ **Category:** Blue Robotics Software\ **Created:** [July 26, 2025, 10:30pm UTC](https://discuss.bluerobotics.com/t/tether-diagnostics-extension-documentation/21088 "2025-07-26T22:30:16Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![StrikeLines](https://avatars.discourse-cdn.com/v4/letter/s/0ea827/32.png) [@StrikeLines](https://discuss.bluerobotics.com/u/StrikeLines)\ **Post date:** [July 26, 2025, 10:30pm UTC](https://discuss.bluerobotics.com/t/tether-diagnostics-extension-documentation/21088/1 "2025-07-26T22:30:16Z")
Blue, We are trying to use the Tether Diagnostics extension to diagnose our tether, but we can’t find any documentation that explains what we should be looking for in the [results.](https://discuss.bluerobotics.com/t/choppy-video-and-connection-issues/19299/2) Searching the forums turns up [multiple](https://discuss.bluerobotics.com/t/connection-issues-with-fathom-x/17959/2) threads where Blue asks users to [share screenshots](https://discuss.bluerobotics.com/t/how-to-check-the-quality-of-a-tether/18635/2) of their Tether Diagnostics results. Could you please share some screenshots of what a normal and abnormal Tether diagnostics graphs looks like? The first graph in the results seems pretty self explanatory. My values just jump up to about 140 mbps and stay there. The second graph is less clear what is going on… ---
**Author:** ![StrikeLines](https://avatars.discourse-cdn.com/v4/letter/s/0ea827/32.png) [@StrikeLines](https://discuss.bluerobotics.com/u/StrikeLines)\ **Post date:** [July 26, 2025, 10:44pm UTC](https://discuss.bluerobotics.com/t/tether-diagnostics-extension-documentation/21088/2 "2025-07-26T22:44:05Z")
Here are my two graphs from a test this afternoon. This is with a 300 foot standard BlueRobotics tether. Are my values in these graphs normal? And could you explain what we are looking for in the second graph? ![tether diagnostics mbps](https://us1.discourse-cdn.com/flex019/uploads/bluerobotics/original/2X/c/c2103f3ae3433769f040ca064e2d3a4730b5c183.png) ![tether diagnostics output](https://us1.discourse-cdn.com/flex019/uploads/bluerobotics/original/2X/8/848f93bcd1ab1765e9426be3267646f592b8ffd0.png) ---
**Author:** ![tony-white](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.bluerobotics.com/tony-white/32/13297_2.png) [@tony-white](https://discuss.bluerobotics.com/u/tony-white)\ **Post date:** [July 28, 2025, 5:43pm UTC](https://discuss.bluerobotics.com/t/tether-diagnostics-extension-documentation/21088/3 "2025-07-28T17:43:06Z")
Hi @StrikeLines - Apologies, we don’t have any guide material for interpreting the extension (yet) as we are still learning what the results mean ourselves! Generally, if the purple and blue lines are approximately equal and higher than 50, you have a good connection. The second graph looks correct, except the few spikes to 0 are a bit concerning. Are you having issues with your tether connection? Have you measured the resistance or tried using a different tether pair, swapping the connection in the ROV and FXTI box? ---
**Author:** ![StrikeLines](https://avatars.discourse-cdn.com/v4/letter/s/0ea827/32.png) [@StrikeLines](https://discuss.bluerobotics.com/u/StrikeLines)\ **Post date:** [July 29, 2025, 4:56pm UTC](https://discuss.bluerobotics.com/t/tether-diagnostics-extension-documentation/21088/4 "2025-07-29T16:56:35Z")
@tony-white I’ll reply in another thread, because I think my problem is probably unrelated to the tether. ---
**Author:** ![francisco\_cori](https://avatars.discourse-cdn.com/v4/letter/f/8c91f0/32.png) [@francisco\_cori](https://discuss.bluerobotics.com/u/francisco_cori)\ **Post date:** [July 30, 2025, 10:21am UTC](https://discuss.bluerobotics.com/t/tether-diagnostics-extension-documentation/21088/5 "2025-07-30T10:21:53Z")
Hi!! I find this thread really useful. As far I understand I have some issue with my tether and I should expect values of 50 or higher. Sorry for the bad picture quality, I will try to get a better one. ![Imagen de WhatsApp 2025-07-28 a las 11.04.51_0bb3ab4f](https://us1.discourse-cdn.com/flex019/uploads/bluerobotics/original/2X/5/552c10a0b1d65c66f5b5dc1f742b26bf7a8414fe.jpeg) ---
**Author:** ![tony-white](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.bluerobotics.com/tony-white/32/13297_2.png) [@tony-white](https://discuss.bluerobotics.com/u/tony-white)\ **Post date:** [July 30, 2025, 4:50pm UTC](https://discuss.bluerobotics.com/t/tether-diagnostics-extension-documentation/21088/6 "2025-07-30T16:50:21Z")
Hi @francisco_cori - That bandwidth does look a little low. How long and what type of tether are you using? Can you share screenshots from the tether diagnostic extension? Have you measured your tether’s twisted pair resistance with a multimeter, from Fathom-X in the vehicle to Fathom-X in the topside FXTI box? ---
**Author:** ![francisco\_cori](https://avatars.discourse-cdn.com/v4/letter/f/8c91f0/32.png) [@francisco\_cori](https://discuss.bluerobotics.com/u/francisco_cori)\ **Post date:** [July 30, 2025, 5:12pm UTC](https://discuss.bluerobotics.com/t/tether-diagnostics-extension-documentation/21088/7 "2025-07-30T17:12:58Z")
Thanks a lot @tony-white for pointing me out on the good direction cause I was using the wrong diagnostic tool. Now. I have been able to use the tether diagnostic extension and I am getting good result for my 200m length two pair cable. So I can be more confident about the signal quality of my tether. Thanks!! ![imagen](https://us1.discourse-cdn.com/flex019/uploads/bluerobotics/original/2X/5/55c08b3878eabf3e46460cf3f9c2fc0cf2c54c2c.png) ---
**Author:** ![tony-white](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.bluerobotics.com/tony-white/32/13297_2.png) [@tony-white](https://discuss.bluerobotics.com/u/tony-white)\ **Post date:** [July 30, 2025, 5:18pm UTC](https://discuss.bluerobotics.com/t/tether-diagnostics-extension-documentation/21088/8 "2025-07-30T17:18:26Z")
Hi @francisco_cori - I wouldn’t call those good results! Generally, you want the blue and purple lines to be on top of each other, not separated like this. I’d double check your tether resistance and connections… ---
**Author:** ![francisco\_cori](https://avatars.discourse-cdn.com/v4/letter/f/8c91f0/32.png) [@francisco\_cori](https://discuss.bluerobotics.com/u/francisco_cori)\ **Post date:** [July 30, 2025, 7:20pm UTC](https://discuss.bluerobotics.com/t/tether-diagnostics-extension-documentation/21088/9 "2025-07-30T19:20:37Z")
Thanks a lot for your quick answer. I will follow your instructions and perhaps change all the cable for a new one that I bought. ---
**Author:** ![EliotBR](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.bluerobotics.com/eliotbr/32/6937_2.png) [@EliotBR](https://discuss.bluerobotics.com/u/EliotBR)\ **Post date:** [July 14, 2026, 4:19pm UTC](https://discuss.bluerobotics.com/t/tether-diagnostics-extension-documentation/21088/10 "2026-07-14T16:19:49Z")
Came across this post while looking for something else. Noting that there’s (now) documentation available [in the README](https://github.com/Williangalvani/plc-extension#plc-diagnostics) of the Extension, which should also show up in the BlueOS extensions manager when installing it 🙂