Re: Questions on impedance matching


Another way to think of bridging systems, used in audio broadcasting and measuring instruments such as oscilloscopes and voltmeters, is to compare them with your incoming AC power line. You would not want to try to match the source impedance of the line (unless you were Nikola Tesla in Colorado Springs). Bridging allows a large number of devices to be connected and disconnected from a source at random while having a minimal affect on the source or the other connected devices.

For audio, this simple system generally works well in a moderately sized building where connecting lines are limited to about a hundred feet. Longer lines began acting like transmission lines as the characteristic impedance of typical telephone and audio wire is a few hundred ohms at most. For transmission over longer lines, such as in a movie lot with scattered sound stages, low-impedance transmission, and possibly equalization, may be required to maintain high-frequency response.

Bruce, KG6OJI

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