Solution:

The wire length is not the only factor that affects the connection. The wire impedance and environment that the wire runs through has a bigger impact than the wire size and length. The Extender connection is 100 Ohm impedance, and the connecting wire needs to match that. If there is an impedance mis-match, signal degradation will occur. The VDSL is an analog signal that is sensitive to noise. If there is a magnetic field, or electrical noise around the wire, the performance will be affected. Shielded FTP/STP cable is recommended. The claimed distance is based on the ideal situation and it may differ from the real world at user's site. The testing is done on the regular CAT5 24 Gauge wire in our lab. The line needs to be a dedicated line not to share with voice. If there is any filter or splitter added then the performance will be affected.