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Saturday October 28, 2006
Hearing things 
| | Citing widespread interference on broadcast frequencies used by its member stations, National Public Radio has asked the Federal Communications Commission to order recalls of millions of FM modulators that drivers use to play satellite radios and iPods through their car stereos. |
| | A field study by NPR Labs found that nearly 40 percent of those devices have signal strengths that exceed FCC limits, enabling them to break into FM broadcasts in nearby cars with unwanted programming. A separate investigation by the National Association of Broadcasters found that more than 75 percent of the devices it tested violated the power limits. |
| | The interference has spurred complaints from listeners whose favorite public radio and Christian broadcasts have been briefly interrupted by satellite radio shock-jock Howard Stern and other offensive fare. |
| | The illegal FM modulators "have contributed to ... unacceptable degradation of the audio quality of public radio stations," NPR's chief executive officer, Ken Stern, said in an Oct. 12 letter to FCC Chairman Kevin J. Martin. A copy of the letter was obtained by The Sun. |
| | "Left unaddressed," he continued, "these modulators pose a significant threat to the provision of public radio's free, over-the-air public and community service." |
| | On the one hand, NPR has a case. I've noticed that my Sirius satellite radio puts out a signal strong enough to hear up to 30 or 40 feet away, while my Belkin TuneCast II has a signal that barely makes it form the front seat to the back. |
| | There was a report (now 404'd), referenced in posts by Mary Lu and myself last June, that said 3/4 of all tested personal FM transmitters put out signals above the FCC-mandated limits. Mary Lu was pleased with the report, and urged he FCC to enforce its limits. I responded, |
| | I understand and respect Mary Lu's concerns. But I don't know of a single instance where reception of licensed stations has been harmed by one of these little transmitters. Moreover, I own two of the tested devices — the Belkin TuneCast II and the Sirius Sportster SPTK2 — and the original iRock, which is an ancestor of the tested iRock 450FM. All three of those devices failed the test (by being too strong). In practice, however, the iRock and the Belkin are so weak they verge on useless. The Sirius is, I'll agree, pretty strong. For those reasons, I add missing antenna lengths to the iRock and the Belkin (here's that hack, with much more background on the matter) and subtract it from the Sirius, which is also capable of transmitting on 87.7 and 87.9, which are below the used parts of the FM band which most digital and analog receivers are capable of getting. The only station in the country, in fact, licensed to 87.9 is a little (10-watt) station at St. Francis High in Mountain View, CA. Channel 6 audio is on 87.75, and can either interfere with one of these transmitters, or receive interference from them. |
| | But I suspect there are approximately zero problems in this exceptional condition, since even the relatively powerful Sirius radio is blown away at 87.9 by either Channel 6 audio (which I pick up from the station in San Luis Obispo when I drive through that area between here and San Francisco) or by legitimate FM stations on 88.1. In urban regions such as Los Angeles, which are packed wall-to-wall with strong signals (starting with KKJZ on 88.1), most of these little transmitters are at a huge disadvantage. |
| | I still stand by that. What I'd add, at this point, are two recommendation for the FCC: 1) require that car radios carry an AUX input, so sound sources can plug right into a car's amplifier; and 2) require the transmitters to work on 87.7 and 87.9. |
| | Meanwhile, this is almost a complete non-issue. |
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