In the recent letter, “KRKO needs stronger signal,” the writer complained that currently KRKO’s signal is full of static during the day and that it fades at night.
KRKO is an AM (amplitude modulation) station. It uses what we hams (amateur radio operators) call ancient modulation.
Two-thirds of the power of an AM signal is in the informationless carrier wave. Only one-third goes to the modulated portion of the signal – that part that provides the music or voice in the signal. On the other hand, with FM, frequency modulation, all of the signal power is devoted to the information portion of the signal. There is no carrier wave.
The writer complained that KRKO’s signal was full of static. Please conduct the following experiment: The next time there is a thunderstorm listen to an AM station and then listen to a FM station. You will hear tremendous static crashes on AM with each lightning stroke. On FM you may not even hear anything unusual. This is because the tremendously high amplitude of the electrical discharge is meaningless to a receiver designed to respond to changes in frequency.
Fading at night might be the result of phase shift of the AM signal – the back end of the signal arriving at the receiver before the front end of the signal.
The antenna structures for the AM broadcast band are roughly 100 times larger than for the FM broadcast band because the wavelength at the AM broadcast band is about 100 times longer than for the FM broadcast band.
KRKO does not need a stronger signal. Although it is terribly late in the game, KRKO needs to migrate away from the dinosaur era of AM radio by seeking an FM frequency assignment from the FCC.
In the meantime, those citizens impacted by these proposed towers should start boycotting all AM stations. If the revenues dry up the towers will disappear.
Edmonds
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