§ 76.609   Measurements.

   (a)  Measurements  made to demonstrate conformity with the performance
   requirements set forth in § § 76.601 and 76.605 shall be made under conditions
   which reflect system performance during normal operations, including the
   effect of any microwave relay operated in the Cable Television Relay (CARS)
   Service  intervening between pickup antenna and the cable distribution
   network.  Amplifiers  shall be operated at normal gains, either by the
   insertion of appropriate signals or by manual adjustment. Special signals
   inserted in a cable television channel for measurement purposes should be
   operated at levels approximating those used for normal operation. Pilot
   tones, auxiliary or substitute signals, and nontelevision signals normally
   carried on the cable television system should be operated at normal levels
   to the extent possible. Some exemplary, but not mandatory, measurement
   procedures are set forth in this section.

   (b)  When it may be necessary to remove the television signal normally
   carried on a cable television channel in order to facilitate a performance
   measurement, it will be permissible to disconnect the antenna which serves
   the  channel  under  measurement and to substitute therefor a matching
   resistance termination. Other antennas and inputs should remain connected
   and normal signal levels should be maintained on other channels.

   (c) As may be necessary to ensure satisfactory service to a subscriber, the
   Commission may require additional tests to demonstrate system performance or
   may specify the use of different test procedures.

   (d) The frequency response of a cable television channel may be determined
   by one of the following methods, as appropriate:

   (1) By using a swept frequency or a manually variable signal generator at
   the  sending  end  and a calibrated attenuator and frequency-selective
   voltmeter at the subscriber terminal; or

   (2) By using either a multiburst generator or vertical interval test signals
   and either a modulator or processor at the sending end, and by using either
   a demodulator and either an oscilloscope display or a waveform monitor
   display at the subscriber terminal.

   (e) System noise may be measured using a frequency-selective voltmeter
   (field strength meter) which has been suitably calibrated to indicate rms
   noise or average power level and which has a known bandwidth. With the
   system operating at normal level and with a properly matched resistive
   termination substituted for the antenna, noise power indications at the
   subscriber terminal are taken in successive increments of frequency equal to
   the  bandwidth of the frequency-selective voltmeter, summing the power
   indications  to obtain the total noise power present over a 4 MHz band
   centered within the cable television channel. If it is established that the
   noise level is constant within this bandwidth, a single measurement may be
   taken which is corrected by an appropriate factor representing the ratio of
   4 MHz to the noise bandwidth of the frequency-selective voltmeter. If an
   amplifier is inserted between the frequency-selective voltmeter and the
   subscriber terminal in order to facilitate this measurement, it should have
   a bandwidth of at least 4 MHz and appropriate corrections must be made to
   account for its gain and noise figure. Alternatively, measurements made in
   accordance with the NCTA Recommended Practices for Measurements on Cable
   Television Systems, 2nd edition, November 1989, on noise measurement may be
   employed.

   (f) The amplitude of discrete frequency interfering signals within a cable
   television channel may be determined with either a spectrum analyzer or with
   a frequency-selective voltmeter (field strength meter), which instruments
   have been calibrated for adequate accuracy. If calibration accuracy is in
   doubt, measurements may be referenced to a calibrated signal generator, or a
   calibrated variable attenuator, substituted at the point of measurement. If
   an amplifier is used between the subscriber terminal and the measuring
   instrument, appropriate corrections must be made to account for its gain.

   (g) The terminal isolation between any two terminals in the cable television
   system  may be measured by applying a signal of known amplitude to one
   terminal and measuring the amplitude of that signal at the other terminal.
   The frequency of the signal should be close to the midfrequency of the
   channel being tested. Measurements of terminal isolation are not required
   when either:

   (1) The manufacturer's specifications for subscriber tap isolation based on
   a representative sample of no less than 500 subscribers taps or

   (2) Laboratory tests performed by or for the operator of a cable television
   system  on a representative sample of no less than 50 subscriber taps,
   indicates that the terminal isolation standard of § 76.605(a)(9) is met.

   To  demonstrate compliance with § 76.605(a)(9), the operator of a cable
   television system shall attach either such manufacturer's specifications or
   laboratory measurements as an exhibit to each proof-of-performance record.

   (h) Measurements to determine the field strength of the signal leakage
   emanated by the cable television system shall be made in accordance with
   standard engineering procedures. Measurements made on frequencies above 25
   MHz shall include the following:

   (1) A field strength meter of adequate accuracy using a horizontal dipole
   antenna shall be employed.

   (2)  Field  strength  shall  be expressed in terms of the rms value of
   synchronizing  peak for each cable television channel for which signal
   leakage can be measured.

   (3) The resonant half wave dipole antenna shall be placed 3 meters from and
   positioned  directly below the system components and at 3 meters above
   ground. Where such placement results in a separation of less than 3 meters
   between the center of the dipole antenna and the system components, or less
   than 3 meters between the dipole and ground level, the dipole shall be
   repositioned to provide a separation of 3 meters from the system components
   at a height of 3 meters or more above ground.

   (4) The horizontal dipole antenna shall be rotated about a vertical axis and
   the maximum meter reading shall be used.

   (5) Measurements shall be made where other conductors are 3 or more meters
   (10 or more feet) away from the measuring antenna.

   (i) For systems using cable traps and filters to control the delivery of
   specific channels to the subscriber terminal, measurements made to determine
   compliance with § 76.605(a) (5) and (6) may be performed at the location
   immediately  prior to the trap or filter for the specific channel. The
   effects of these traps or filters, as certified by the system engineer or
   the equipment manufacturer, must be attached to each proof-of-performance
   record.

   (j) Measurements made to determine the differential gain, differential phase
   and the chrominance-luminance delay inequality (chroma delay) shall be made
   in accordance with the NCTA Recommended Practices for Measurements on Cable
   Television Systems, 2nd edition, November 1989, on these parameters.

   [ 37 FR 3278 , Feb. 12, 1972, as amended at  37 FR 13867 , July 14, 1972;  41 FR 10067 , Mar. 9, 1976;  42 FR 21782 , Apr. 29, 1977;  49 FR 45441 , Nov. 16, 1984;
    57 FR 11004 , Apr. 1, 1992;  57 FR 61011 , Dec. 23, 1992;  58 FR 44952 , Aug. 25,
   1993]

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