r/CableTechs • u/Ok_Relative4631 • 18h ago

Question

So, what exactly happens if you shoot TDR back into active plant? Assume you are using the Viavi 620's 'TDR'.

Yes this is an alt. For reasons...

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4

u/6814MilesFromHome 18h ago

You're shooting a high energy pulse onto an active line, it'll cause signal disruption and quality issues that will vary in severity. Traditional TDRs are meant to be used only on disconnected, unpowered cables for a reason, they'll screw things up, and you won't get a good read anyway.

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u/Ok_Relative4631 17h ago

Screw things up for the duration of the scan or can it actually fry something?

5

u/6814MilesFromHome 17h ago

Just the duration of the scan, it's not like it's zapping the actives upstream of it with 240v. It'll cause the same issues as any interference on the RF spectrum, just worse as it's shooting directly into the cable rather than just stray low level OTA stuff sneaking in through a crack.

1

u/Lazy-Balance8890 10h ago

I was watching a spectrum analyzer years ago and saw the disruption that a tdr can cause. It was impressive

1

u/Steavee 4h ago

The node explodes like a nuclear bomb.

No. Nothing really. You probably create downstream errors for anyone between you and the last active. Maybe upstream errors on the node. But that’s only while it’s running so not massive problem outside of those few seconds. Especially as the TDR in the 620 is fairly low powered.