Hey, keep the 'lecture' going, I was just beginning to understand! Seriously, thanks to all for clearing up what this is (a capacitor), what rating it is and how to interpret, and its function. I remember now that a capacitor is wired (across/in series with?) the terminals of a tweeter to act as a high-pass filter, so perhaps that's how it works in the antenna, filtering out high frequency 'noise'.

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1986 560SL
2002 Toyota Camry
1993 Lexus