ANSI SCTE 03 pdf free download
ANSI SCTE 03 pdf free download.Test Method for Coaxial Cable Structural Return Loss.
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, 25 1-500 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.
8.2. Perform a Calibration
Perform a calibration (error correction) for each frequency range following the manufacturer’s instructions. For a vector network analyzer, this is a 1-port open/short/load calibration.
8.3. Connect to Network Analyzer
Connect the cable under test to the network analyzer test port. Terminate the far end of the cable with a 75 ohm matched termination. Measure the return loss over the frequency span.
8.4. Re-Normalize the Return Loss
Using a computer, or built in analyzer function, re-normalize the return loss to the average impedance value of the cable, as measured in ANSI/SCTE 66 2008.
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 V ector 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. Notice that test equipment generally displays the decibel representation of the reflection coefficient, which is a negative number whenever the reflected power is less than the incident power (Prenected < Pincident). Esentially, the test equipment is displaying the return“gain” rather than the return “loss.” Thus, the results are often displayed as negative numbers, even though the“returm loss” will always be positive when Prenected < Pineident.
The difference between this maximum value and the measured SRL level is the maximum positive error. These are only example values; consult with the equipment manufacturer to determine the actual error values. 11.3. Add Cable 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.ANSI SCTE 03 pdf download.
