SICK SIGNAL
posted by James Reel
For the past couple of days, sometimes it’s sounded like a lot of CDs have been mistracking—“skipping”—as have, strangely, our spoken announcements. The problem, as it turns out, has nothing to do with bad CDs, stuttering announcers or anything else originating in the control room. It’s about a malfunction along the path the signal takes from the studio to the transmitter.
Our studio is on the University of Arizona campus. Our transmitter is several miles away, atop Mt. Bigelow in the Catalinas. In olden times, to get the audio out of the control room and up to a transmitter some distance away, radio stations had to use telephone lines—the frequency range was slightly better than the lines that fed into your home phone, but not much, and that’s why the audio quality on CD reissues of some old radio broadcasts (like those of Pierre Monteux with the San Francisco Symphony) is so poor, even by the standards of the 1940s and ’50s. In the 1970s, most of those phone lines were replaced by satellite transmission for national and international coverage, and microwave transmitters/receivers at the local level. Yes, microwaves, the same technology that helps you reheat your coffee in the morning. Now, these are signals that are beamed from one specific point to another (the studio to the transmitter site), and you cannot pick them up on your radio. Once the signal gets out of our signal and is delivered by microwave to the transmitter, then it’s transformed into a different kind of radio wave that’s beamed out in a wide pattern from an antenna atop the transmitter tower, and that’s something you can pick up on your home or car radio.
It’s nice to have a transmitter on a mountaintop, because that means broad coverage in the valley below. But it’s not so nice in the summer, when lightning strikes frequently knock the signal out, and it’s especially troublesome in the winter, when ice builds up on the antenna. If the ice gets too thick, the transmitter will automatically lower its output power to compensate for reflected power under the ice. That means a weaker signal to you.
And there’s another problem: When ice builds up, our microwave studio-transmitter link is, in the official phrase, “susceptible to interruptions.” In other words, it cuts out or sounds like hell—as you’ve heard over the past couple of days. The engineers seem to have things under control at the moment, but Mt. Bigelow is a lot colder and wetter than down here where we live. Expect more trouble over the next three months.
Of course, you can avoid all this by listening to us online.
