ANSI SCTE 62-2018 pdf free download.Measurement Procedure for Noise Figure
1.2. Scope
This procedure defines a method of measurement for Noise Figure of active Cable Telecommunications equipment. It is intended for measurement of 75-ohm devices having type “F” or 5/8-24 KS connectors,and for the measurement of true broadband noise as opposed to narrowband disturbances.
Test equipment characteristics limit this procedure to frequencies no lower than 10 MHz. See Appendix 3 – Low-Frequency Measurements for a further discussion of evaluation below 10 MHz.
1.3. Benefits
Uniform method of testing and measuring noise figure of active devices.
1.4. Intended Audience
Manufacturers and technical operations.
1.5. Areas for Further Investigation or to be Added in Future Versions
As networks evolve this procedure may be updated to encompass future needs.
2. Normative References
The following documents contain provisions, which, through reference in this text, constitute provisions of this document. At the time of Subcommittee approval, the editions indicated were valid. All documents are subject to revision; and while parties to any agreement based on this document are encouraged to investigate the possibility of applying the most recent editions of the documents listed below, they are reminded that newer editions of those documents might not be compatible with the referenced version.
4. Compliance Notation
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8. Procedure
1. With the DUT connected into the setup and powered, allow time for the DUT to warm up and
stabilize before making measurements.
2. Set the ANFM according to the manufacturer’s instructions for measurements at the desired
frequencies. Generally, the measurement mode selected will be corrected NF. In this mode, the
system calculates the DUT NF from measurements of uncorrected NF and DUT gain. The
concept is explained in Appendix 1 – Uncertainties and Corrections.
3. If desired, an oscilloscope (connected to the ANFM outputs provided for that purpose) can be
used to graphically display the variation of NF and gain versus frequency. Also, a measurement
of uncorrected NF can be made to show the magnitude of the correction being made for second-
stage noise.
4. Record the test results. A suggested format is given in Appendix 5 – Test Report.
The modern ANFM makes measurement very quick and convenient. However, in order to properly evaluate the results, some knowledge of the sources of error and means to minimize them is necessary. To begin with, we should differentiate between avoidable and unavoidable errors. One class of avoidable errors results from poor setup conditions. A noisy environment and inadequate shielding can allow extraneous signals to pollute the measurement. An oscilloscope connected to the ANFM scope / recorder output will usually show this. Before resorting to the ultimate solution of a shielded room, the integrity of all connections and quality of cables should be checked in order to eliminate or minimize the problem. Dirty or worn items can cause signal loss or intermittent readings, and must be cleaned or replaced. Another avoidable error stems from the fact that the noise figures of many devices vary with source impedance. Since the noise source is switched between “on” and “off” states in making measurements, its output impedance could vary and affect the reading. Using a quality noise source such as that suggested can make this effect negligible.
