ADSL and AM radio interference ... once again (18 September 2000) There was a Sunday Times article yesterday on complaints being made to the Government by the broadcasting industry and Radiocommunications Agency on the possibility of ADSL interfering with AM radio. This is most odd, as there have been lengthy OFTEL consultation processes on broadband Internet access. Although we have complained before about the slowness of such processes, the extreme length of time they take at least allows every conceivable issue to be discussed, and interference issues were indeed examined at huge length [1MB Adobe Acrobat file] but without definite conclusions. Unfortunately, public documents appear not to exist after mid-1999. In any case, what equipment and frequencies are to be used has been common knowledge for some time, so why wait until after BT Openworld and other services are launched before complaining? Furthermore, from Web searches, we can find a lack of documented instances of AM interference although it is recognised as a possible problem. Even the Radiocommunications Agency is casting around for concrete examples; a currently incomplete draft of its position is inconclusive. We wonder whether the engineering tests which supposedly demonstrate the AM radio problems were carried out in real homes or on a laboratory bench. (In passing, it is worth noting that most references are to AM radio causing xDSL interference, not the other way round!) A particularly telling study is on the Radiocommunications Agency's own site, which states (5.4): Most of the future items talked about involved a connection with the Internet in some way. This would involve an increase in bandwidth. Asynchronous Digital Subscriber Line (ADSL) technology could be used to provide broadband Internet access as it will allow a superfast connection which is 'always on'. As it is unlikely that only one company will install these lines, there is an increased potential for interference between mismatched cables running through underground ducts. There is some worry that Internet connections through ordinary phone lines will be endangered by electromagnetic interference if many companies offer this service. However, it is conceded that competition is required to prevent one company, such as BT, from maintaining a monopoly. No mention of problems within the home - and not unbundling the local loop is, it would seem grudgingly, considered more of a problem than that of electromagnetic interference. One of our mailing list subscribers pointed out that neither solution mentioned in The Sunday Times' article would be satisfactory. Installing a choke on the line would change its impedance, probably reducing the available bandwidth; cutting the line power would result in the range from the local exchange being reduced, thus resulting in fewer people being able to receive ADSL. Frankly, the possibility ('engineers believe', 'potentially affecting') of interference to an AM radio next door at furthest seems a feeble reason to kick up a fuss. It seems, from the Option 2 Implementation Subgroup site (the definitive source on how local loop unbundling is shaping up), that the Radiocommunications Agency, rightly or wrongly, lost the battle [30KB Word file] with the telecommunications industry but is continuing hostilities.