Interference on the medium waves generated by battery-powered cars has prompted several manufacturers (Audi, BMW, Mini, Tesla, and Volkswagen) toeliminate the AM tuner in their battery-powered models (we’ve already discussed it here). But new radio disturbances are on the horizon on which it would be difficult to act. Raising the alarm is the ITU (International Telecommunication Union): induction charging systems generate harmonic frequencies between 500 and 700 kHzthat cannot be eliminated by shielding because they are picked up by the antenna. In theory, U.S. law prohibits interfering with licensed stations, so if electric cars disrupt broadcasters, it is up to manufacturers to comply. Technically, however, it is not easy, and since the electric market moves huge interest (by 2030 in the U.S., one out of every two new cars should be electric) the game is wide open.
Heavy interference, but there may be a solution
Induction charging is convenient because it avoids the use of a cable. But the high powers involved (10 kW for a car, 100 kW for a public service bus) produce “robust” phantom signals. There is also DWPT, based on the same technology, which is used to extend the range of cars (now limited to a few hundred kilometers). It relies on coils placed under the asphalt that transfer energy directly to vehicles that do not have to stop at designated charging stations. What to do then? According to Xperi, stations could transmit digitally with the HD Radio system (for which the company owns the patent) because signal processing and error correction provide greater immunity to noise. (Written by Fabrizio Carnevalini)
The abandonment of thermic engines is a mandatory goal to reduce CO2 emissions. The automotive industry is getting ready and among the aspects that are being discussed, there is also radio listening. On electric cars, HF interference is generated primarily by the frequency converter, a device that controls the amount of power delivered by the electric motor by turning the voltage on and off thousands of times per second. This generates signals that fall in the medium wave broadcast band: electrical noises (such as distortion and crackling) similar to those emitted by smartphones, TVs, computers, vacuum cleaners and hair dryers. In addition, static electricity, which creates crackles, increases with the power of the motors. So much so that some manufacturers, such as BMW, Mini, Tesla and Volkswagen have eliminated the AM band on their current cars. Others, like General Motors, are studying the problem, but the solution isn’t around the corner. Xperi Corporation, a leading digital radio company, whose HD Radio standard (a patent it owns) is used both in the FM and AM band, claims that its transmission system is not afraid of interference. And it presented test results at NAB Broadcast Engineering and Information Technology, the annual conference of American broadcasters. According to Pooja Nair, an engineer at Xperi Corporation, a fully digital AM signal resists interference much better than an analogue one.