Calculate the length of the line from DSLAM to BOX

Hello, I find this post a bit late.

If I remember correctly the words of the itinerant technician from FREE who came to my place,

by connecting the multimeter to the cable pair, we should observe about 50 nanofarads per kilometer of cable

That is, 100 nanofarads if there are two kilometers
150 for 3 kilometers...

These are just my memories. It’s information to be confirmed.

I hope this can help you.

Hello,
capacity measurement (multimeter capacitance meter) is only possible on an open line (disconnected at both ends) and the measured value (capacitance in nanofarads between the wires) only indicates a very approximate value of the length as it is highly dependent on the type of cable used (4/10 or 6/10) and over what length?
Indeed, a line typically passes through one, two, or three sub-distributors and changes cable each time.
An ohmmeter multimeter does not allow for precise measurement at this level: a short circuit would need to be created at the other end and the loop resistance measured, then divided by 2 to find an approximate length based on the known resistivity of the cable, as this too, like capacitance, is not significant until the proportion of each type of cable in the line's constitution is known.
The only reliable value for length is therefore the constitution found in the FT databases and used for accessibility estimates.
The attenuation is theoretically calculated from this constitution by adding the theoretical attenuation of each type of cable in relation to the length used on your line.

--
and... There you go!

If it works, I'm interested to know how it feels :)

Otherwise, there is a device that allows you to see your distance as well as whether you have a short circuit or an open circuit, but it's expensive and I forgot the name :D (I'll mention it if I remember)
However, from what I used, if I remember correctly, the measurements correspond well to what degrouptest indicates (within a few tens of meters).

As for the calculation, it seems to me that with the diameter of the cable, the impedance over 100m, or something like that, there must be a magic formula ^^
Maybe a message to post on an electricity forum.

Also to test Nahu's method :)

Hello,

This information is usually referenced in the database of the historical operator: France Telecom, since it is FT that is responsible for this cabling.

It is this database that is normally queried by eligibility tests to estimate which services will be feasible.