The uncertainties of digital terrestrial broadcasting technologies have been highlighted on both sides of the Atlantic in the last couple of days. Survey house Centris, as reported in the Boston Globe, suggests that millions of US homes will get fewer or no off-air TV signals once digital switchover is complete next February. The study (I can't cite it directly as it appears to be unpublished and even unidentified on the company's website) claims to have investigated signal characteristics in many US cities and estimated reception probabilities accordingly. The BG article claims that at least 50% of viewers using set-top aerials will fail to get a digital signal. Others will have problems with trees and walls. There is nothing new in any of this. The problems with the ATSC system have been well rehearsed over many years. It's not that it doesn't work. It is just that it is impossible to know when it will or won't work. And that is a killer when it comes to selling digital TVs, converter boxes and new digital channels. Is a similar issue now spelling the end for DAB, the digital radio standard used in the UK and some other countries? Yesterday GCap, one of the UK's leading commercial radio broadcasters, announced that it will close two of its leading DAB stations, TheJazz and Planet Rock (the latter ironically described as "award-winning" in the CEO's website introduction), and sell its 63% stake in Digital One, the DAB promotional group, to Arqiva, the broadcast infrastructure provider. According to GCap DAB "cannot be an economically viable platform" with its current cost structure. As I noted previously, DAB has had some success in the UK: it now accounts for 10% of all radio listening. But the network rollout has been frustratingly slow and patchy, and while "coverage" is claimed at 85% of the population, residents outside major towns and cities still struggle to get a usable service. The problem is similar to that in the US DTV market, in that users in marginal areas are encouraged to install a roof-top antenna to enable reception. And a professional installation multiplies the £40 invested in the DAB receiver several times over. I'm sure DAB is a wonderful thing if you can get it (although there have been complaints about reduced audio quality). My neighbour 10 yards across the road is pleased with her set. But I had to return mine to the retailer because it wouldn't receive a signal. That's how uncertain the system is, and it's not good enough for a service that aims eventually to replace analogue broadcasting through a retail, open standards model. The many millions of investment needed to correct those problems are one of the factors GCap will have looked at, and why they have the passed the buck back to the owners of the broadcast infrastructure. Likewise in the US, as the DTV convertors leave the retailers' shelves and reach customers' homes, the real test will be when they start getting returned as unusable, or simply gather dust. Some users will be lucky: many others will simply give up and switch to cable or satellite, or indeed stream or download from the Internet. Client Reading: Broadcast Under Threat: Over-The-Top Video Distribution