ANSI SCTE 16 pdf free download

ANSI SCTE 16 pdf free download.Test Procedure for Hum Modulation.
1.3. Benefits In a coaxial telecommunications system, AC power and radio frequency (RF) signals can exist on the same conductor. As a result, amplitude modulation of the transmitted signals at the power line frequency (hum modulation) can occur in both active and passive equipment due to excesive ac voltage at the output of a local power pack (in the case of an active device) or from parametric modulation of magnetic components (used in circuitry to separate power and signal voltages) in active or passive devices. In North American NTSC analog television systems, the frame repetition rate is 59.94 Hz and the commercial power frequency is 60 Hz. Amplitude modulation of the transmitted signals at the power line frequency (hum modulation) can cause picture disruption in the form of horizontal bars or brightness variation. Excessive hum modulation could also disrupt AGC circuitry commonly used in RF amplifiers, causing excessive RF level variations in the HFC plant. The FCC (Title 47, Part 76.605) requires that hum modulation does not exceed 3% of the visual signal level. This test procedure for hum modulation, when executed according the procedure, will yield confidence in the measured hum modulation performance of the active or passive broadband RF telecommunications equipment under test. Use of this test procedure provides a means for the user to verify acceptable performance of the unit under test. 1.4. Intended Audience The intended audience for this test procedure includes manufacturers, corporate engineers, technical operations, and technicians.
6. Background In a coaxial telecommunications system, where AC power and radio frequency (RF) signals exist on the same conductor, hum modulation of a television signal is measured as a comparison between the modulation envelope (created by line power distortions of the RF carriers), and the peak voltage of the sync tips of the video signal. In a laboratory test environment, the video signal is replaced with a sine wave RF carrier. Under these conditions, the only modulation existing on the carrier is the line power related distortion (created by the device under test) of that carrier. Hum modulation is determined as a function of the line frequency current passing through the device by comparing the peak to peak modulation envelope of the power line distortion to the peak voltage of the carrier by utilizing a diode detector. Due to the non-linear characteristics of any diode detector, it is inaccurate to simply compare the AC modulation voltage and the rectified DC carrier voltage directly due to the voltage drop across the diode. Instead, the modulation voltage is compared to a calibrated change in the rectified carrier. There are two time- domain methods for measuring hum modulation in a laboratory environment, which are detailed in this procedure. These methods are commonly referred to as the 1 dB delta method, and the differential voltage method. These methods are described in Appendix 5.ANSI SCTE 16 pdf download.