AM radio uses the low frequencies where radio began, which have much longer wavelengths. While FM antennas are relatively small and mounted high on towers, AM’s longer wavelengths use the entire tower as an antenna, along with a network of underground wires that typically surround the tower in a circle as wide as the tower is high. Experts in the black art of AM facility design recommend that AM towers’ height be a precise fraction, such as one-quarter, of the station’s wavelength so that the tower will resonate with the frequency. Stations with lower frequencies tend to have higher towers. Old-timer KOAC in Corvallis, Ore.
Talk about collaboration! A typical FM/TV tower can be home to dozens of antennas for stations and other spectrum users. Five full-power TV stations and five FM broadcast from Pinnacle Hill in Rochester, N.Y. (right). Some FM translators and two-way radio and mobile users also share the tower. Pubcaster WXXI owns the middle tower and uses it to broadcast its TV signal and two FMs.
1 These are UHF TV antennas, typically 40-50 feet in length.
Iowa Public Radio’s KUNI-FM in Cedar Falls is again broadcasting at full power after several weeks of suffering from ice-storm damage. The network’s classical KHKE-FM, also in Cedar Falls, remains at low power after sustaining damage in another storm.
At Mountain Lake Public Broadcasting in upstate New York, Alice Recore put $1.2 million into reinforcing and preparing WCFE’s 30-year-old tower for the DTV age. Across the continent at KSPS in Spokane, Wash., Bob Wyatt assiduously maintained and upgraded the station’s 40-year-old tower. But that wasn’t enough in either case. Both towers suffered catastrophic collapses within the past year, at costs that are still mounting. Theoretically, towers don’t have to fail.