ANSI SCTE 03-2016 pdf download
ANSI SCTE 03-2016 pdf download.Test Method for Coaxial Cable Structural Return Loss
4. Compliance Notation
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6.1. SRL
SRL on cables is typically tested on whole reels. The tests are to be performed from each end of the cable. The cable to be tested must be terminated in a proper load. A fixed 75 ohm termination is sufficient for normal cable lengths. The effect of the end termination is reduced by twice the cable loss, such that for long lengths of cable, the end termination is not significant. For shorter lengths of cable, the end termination return loss plus twice the cable loss must be added to the error analysis.
It may be possible to take a single sweep of the network analyzer with sufficient resolution to see the SRL peaks. The resolution of the measurement can be increased by making several full band sweeps with slightly offset start frequencies, changing the start and stop frequency to obtain the required resolution each sweep, until the entire range is covered. For example, 995 MHz divided by 1601 points yields about 600 kHz per point, thus four sweeps starting at 5.00 MHz, 5.15 MHz, 5.30 MHz and 5.45 MHz would be needed to ensure proper coverage. As an alternate method the band can be broken into 4 segments 5-250 MHz, 251-500 MHz, 501-750 MHz and 751-1002 MHz. Some newer network analyzers will be able to have a higher number of points (e.g., 6404) and can make the measurement in one sweep. For some analyzers, it may be necessary to slow the sweep time to ensure good measurements, especially on long cables. Consult manufacturer’s information for recommended sweep times.
8.6. Sample Display
Notice that the trace may rise at higher frequencies. This is often caused by connections used to make the transition from the Network Analyzer to the cable. The best possible connection is necessary for good results. Connector compensation techniques (capacitance adjustment) may be used to reduce connector effects. Time domain gating (such as found on many performance Vector Network Analyzers) can also remove connector effects, but care must be taken not to exceed the many constraints of the time domain transforms; consult with manufacturers’ instructions.
For short lengths of cable, an additional term must be added to the above error equation. The value of this term is the return loss of the far end termination (in dB) plus twice the loss of the cable at the frequency of interest. This term is treated in the same way as the directivity and connector terms. This term is typically negligible for whole cable reels.
