Ofcom Find “no evidence” for Claims of Interference from VDSL Broadband

A new study from the UK telecoms regulator has found “no evidence” to support claims made by the Radio Society of Great Britain (RSGB), which had complained that Openreach’s (BT) VDSL2 based Fibre-to-the-Cabinet (FTTC) broadband technology had “resulted in interference to radio reception.”

In an FTTC setup Openreach will generally run a fibre optic cable to your local street cabinet (DSLAM), while the remaining connection into homes is done over existing copper cable via Very High-bit-rate Digital Subscriber Line (VDSL2) technology. The VDSL2 technology, as currently implemented in the United Kingdom via BT, harnesses up to 17.66MHz of spectrum frequency.

The “noise” from a DSL line can often be detected by tuning an analogue radio to the right setting and then holding it near to your DSL modem/router, although this should only be audible when in very close proximity and will fade away with distance. However faulty kit (e.g. AC adapters) can separately cause problems like Repetitive Electrical Impulse Noise (REIN), which may interfere with VDSL and radio amateurs.

In this case the RSGB, which predominantly represents radio licensed amateurs, highlighted three examples to the regulator where it believed that Openreach’s roll-out of VDSL2 was causing interference for their members in bands from 1.8-14MHz and at distances of between 20 – 160 metres. Ofcom agreed to assess the claims by carrying out surveys (a physical examination of the affected station and tests using calibrated apparatus) at the locations: 2 in North London and 1 in Nottinghamshire.

The regulator’s “overall conclusion” was that there was “no evidence” that emissions from Openreach’s VDSL copper drop wires were causing harmful interference to amateur radio reception. However it’s noted that Openreach engineers had previously “carried out tests at each site and identified and rectified some issues, i.e. rebalanced lines.”

Ofcom’s Conclusion

The test methodology was designed to assess the effect of electromagnetic emissions from BT Openreach VDSL technology on amateur radio reception.

Noise floor measurements were taken from all three sites and compared with that of Baldock radio monitoring station, this showed that the base noise floor levels were comparable at all locations.

Tests at the two North London test sites on the bands that the complainant’s regularly use and where suitable antennas were in use, showed that there were no abnormal levels of electromagnetic disturbance capable of causing harmful interference to radio reception.

Tests carried out at the third site indicated that the problems affecting [REDACTED] were likely to be associated with the extremely close proximity of his antenna to an BT Openreach drop wire ([REDACTED] stated he would ask Openreach to reconfigure their system to relocate the particular cable).

The study itself is short and quite interesting to read (here), although its conclusions probably won’t put a complete end to the concerns expressed by some radio amateurs.