ANSI SCTE 66-2016 pdf free download – Test Method for Coaxial Cable Impedance.
1.1. Scope
The purpose of this procedure is to provide instructions for measuring coaxial cable impedance.
The cable impedance as a function of frequency is calculated from a vector (magnitude and phase) return loss. The average of this impedance across the desired frequency range is the cable impedance. This may be automated, but requires a vector network analyzer, and may be subject to errors due to the cable connection.
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3. Abbreviations and Definitions
3.1. Definitions
Return Loss: The ratio of reflected signal to incident signal, expressed in dB Network Analyzer An instrument used to measure the swept frequency response of a cable
4. Test Samples Cable impedance is typically tested on whole reels of coaxial cable and two (2) tests are performed, one from each end of the cable. The cable to be tested must be terminated with a precision connector and a fixed, precision 75 ohm load for normal cable lengths. The effect of reflection from the end termination is reduced by twice the cable loss, such that for long lengths of cable, the precision of the end termination is not significant. For shorter lengths of cable, the end termination return loss plus twice the cable loss must be included in error analysis.
The input cable connector must be a good impedance match to the cable impedance or the measurement results will be affected. The cable must be prepared according to both the cable and connector manufacturer’s instructions. Improper cable preparation can be a major source of error in impedance measurements.
5. Equipment
Network analyzer with impedance measuring capability, such as Agilent ENA Series, including fixed impedance (75 ohm) test bridge or equivalent
Calibration kit, such as Agilent 85036B or equivalent
Computer or built in analyzer functions to process fixed impedance data
Termination (75 ohm load) for far end cable termination (the load in the calibration kit may be used)
Two (2) test port to cable precision adapters for the size of cable under test
Equipment setup is shown in Figure 1.ANSI SCTE 66 pdf download.