tag:blogger.com,1999:blog-8104908437911552400.post7342760391624260084..comments2024-03-13T10:36:05.451-07:00Comments on The Mighty 1090 KAAY: The Beatles On KAAY (Teenage Wasteland I)http://www.blogger.com/profile/17570209125522920917noreply@blogger.comBlogger1125tag:blogger.com,1999:blog-8104908437911552400.post-9606212429046136752013-05-25T14:56:18.528-07:002013-05-25T14:56:18.528-07:00Felix was right. Anything below 100 cycles or so ...Felix was right. Anything below 100 cycles or so on AM radio is wasted power. And because low frequencies stay there longer, they eat power that could be applied to the "music frequencies."<br /><br />In general, telephones are limited to 300-3000 Hz and we all agree that this is inadequate, so the choice of a low-frequency cutoff is a judgment call. <br /><br />On the other hand, the FCC requires Am stations to pass (relatively) flat and (relatively) distortion-free frequencies down to 50 Hz, so it may be that KAAY would not pass an audio proof of performance with the 70 Hz hi-pass filter in place. But KAAY of my era would not pass an audio proof at all.<br /><br />Capacitors get old and the first thing to go is the low frequencies. Because the circuit is designed to work with the proper value of capacitance, the result can be low-frequency distortion of the low frequencies. Because distortion tends to generate harmonics and because those harmonics fall up in the "music frequencies," low frequency distortion can raise havoc with processing and the audio.<br /><br />It gets worse. Harmonics aside, Intermodulation Distortion can cause one part of the audio to "modulate" another part of the audio. As an example, if you were speaking while I was injecting a distorted 50 hz wave that was rich in harmonics, you might not be able to hear it but it might modulate your voice at a 50-hz or even a 150-hz rate, Even if we couldn't identify the effect, we would all agree that it sounds pretty weird in an undefinable way. When you hear an AM station that sounds weird, they probably have some Intermodulation Distortion thin their chain.Hollis W. Duncannoreply@blogger.com