Attachment 1 Reference Test Methods for Examination of Cable Broadcasting and Television

Attachment 1 Reference test methods for examination of cable broadcasting and television systems

1.Test method for electric wave leakage:

(1)Instruments required:

1.Half-wave dipole antenna, calibrated;

2.Band-pass filter;

3.Pre-amplifier; and

4.Wave leakage tester.

(2)Test procedure:

1.Test 3/4 or more of the total length of aerial lines above feed lines (included) in the entire area and document the locations where the upper limit of maximum wave leakage is exceeded,amount of wave leakage, wave leak age frequency and measurement distance.

2.The test result shall not exceed the upper limit of wave leakage specified in the Specifications. Exceeding the upper limit is considered failing to meet the Specifications.

3.For frequency bands within the range from 225 to 400 MHz, the accumulated wave leakage index exceeding 64 is failure to meet the Specifications, and will be reported to the competent authority immediately.

1 n

Accumulated wave leakage index=10·log(－ 2)

i=1

ｎ:Number of locations where the eave leakage is greater than or equal to 50μV/m.

:Wave leakage measured greater than or equal to 50μV/m at the measurement distance of 3m.

:Fraction of length of cable accutally used for wave leakage measurement equal to length of wave leakage cable divided by the length of cable in the entire area (no less than 0.75)

(3)Test steps:

1.See Figure 1 for test setup.

2.Adjust the length of dipole antenna to half of the wavelength to be tested multiplied by 0.95; or adjust the antenna length according to the frequency length chart provided by the antenna manufacturer for the antenna used, if any.

3.Place the antenna 3m from the coaxial cable to be tested and more than 3m from the ground or other conductive body.

4.Rotate the antenna on the horizontal plan and document the maximum wave leakage. The wave leakage is calculated as: E=V+D+L-G

Ｅ: wave leakage (dBμV/m)

Ｖ: spectrum analyzer reading (dBμV)

Ｄ: dipole antenna factor (dB/m)

Ｌ: loss from antenna to spectrum analyzer(dB)

Ｇ: pre-amplifier gain (dB)

In case that the dipole antenna factor is not provided, it can be determined as:

D=20log(f)-33.7

Where ｆis the test frequency in MHz.

5.For wave leakage test on a frequency lower than 54MHz or higher than 216MHz, if the measurement at 3m is greater than 67μV/m, move the antenna to 10m from the coaxial cable, repeat Step 4 and document the maximum wave leakage.

2.Test method for carrier level:

(1)Instruments required:

1.Adjustable band-pass filter or band-pass filter for the channel to be tested (with noise bandwidthofat least 6 MHz).

2.Variable attenuator.

3.Spectrum analyzer(with resolution bandwidth of 300kHz)

(2)Test procedure:

1.At least 6 points shall be taken for examination based on the number of villages/boroughs in the examination area as per ordinary level 1 of AQL 4.0 standard.In addition, for the distribution network for which microwave is used for transmission, one additional examination point shall be taken at the end of that microwave transmission network. One examination point is taken from every sub-carrier station for the areas of no arrival for a reason, and up to 6 points can be taken.

2.The test points selected shall be representative of the video and audio quality of the entire system. 1/3 or more of the test points shall be selected from the subscribers at the very end of the distribution network.

3.Measurement shall be taken at every subscriber terminal (or tap) selected for the testing. The system fails to meet the Specifications if any of the test points selected fails to meet the criteria set for the Specifications.

(3)Test steps:

1.See Figure 2 for test setup.

2.Tests shall be done using aspectrum analyzer.

3.Test method for carrier to noise ratio:

(1)Instruments required:

1Adjustable band-pass filter or band-pass filter for the channel to be tested (with noise bandwidthofat least 6 MHz).

2.Variable attenuator

3.Pre-amplifier (gain: 20 to 30dB, noise index < 10dB)

4.Spectrum analyzer(with resolution bandwidth of 300kHz)

5.Thermometer (capable of measuring from -20°C to +60°C)

(2)Test procedure:

3.5 channels shall be selected for each examination point for systems with bandwidth smaller than 750MHz. For bandwidth greater than 750MHz, one additional channel shall be selected for every additional 100MHz. The bandwidth less than 100MHz is considered 100MHz. The channels selected for testing shall be distributed evenly across low, medium and high bands. The system’s carrier to noise ratio fails to meet the Specifications if any channel selected for testing at any point fails to meet the criteria specified for the Specifications.

(3)Test steps:

1.See Figure 2 for test setup.

2.Document the temperature at the time of testing.

3.Adjust the spectrum analyzer as follows:

Resolution bandwidth: 300kHz

Video bandwidth: 100Hz (do not exceed300Hz)

Vertical scale: 10 dB/grid

Horizontal scale: 1 MHz/grid

Scan time: set at automatic

4.Without any input, adjust the input attenuation of the spectrum analyzer so that the lower limit of noise ratio is 70dB or more lower than the top of the scale.

5.Adjust the analyzer to the video carrier frequency of the channel to be tested.

6.In case that the channel to be tested is modulated, adjust the analyzer as follows:

Resolution bandwidth: 1MHz or 3MHz

Video bandwidth: 10kHz

Vertical scale: 2dB/grid

Spread spectrum rage: 10kHz

Scan time: set at automatic

7.Adjust the band-pass filter and fine-tune the analyzer to capture the maximum reading other video carrier.

8.Adjust the variable attenuator so that the peak of video carrier falls on the topmost scale line of the analyzer. This line is the reference line for the test.

9.Re-adjust the analyzer as in Step 3.

10.Adjust the analyzer so that the video carrier peak is located at the center of display.

11.Turn off the channel to be tested or at least remove the modulation signal (for the purpose of this test, do not select the carrier used for automatic gain control or automatic slope control).

12.At where the frequency is greater than the video carrier frequency, select a point of which the energy is the minimum on the analyzer. This point is usually located approximately 2-3MHz to the right hand side of video carrier. Adjust the center frequency of the variable band-pass filter to this point and document the dB difference between this point and the topmost scale line.

4.Test method for carrier composite beat ratio:

(1)Instruments required:

1.Variable attenuator

2.Adjustable band-pass filter or band-pass filter for the channel to be tested (with noise bandwidthof1 to6 MHz).

3.Spectrum analyzer(with resolution bandwidth of 30kHz and video bandwidth of 10Hz)

(2)Test procedure:

3.5 channels shall be selected for each examination point for systems with bandwidth smaller than 750MHz. For bandwidth greater than 750MHz, one additional channel shall be selected for every additional 100MHz. The bandwidth less than 100MHz is considered 100MHz. The channels selected for testing shall be distributed evenly across low, medium and high bands. The system’s carrier composite beat ratio fails to meet the Specifications if any channel selected for testing at any point fails to meet the criteria specified for the Specifications.

(3)Test steps:

1.See Figure 2 for test setup.

2.Adjust the spectrum analyzer as follows:

Resolution bandwidth: 30kHz

Video bandwidth: 10Hz

Vertical scale: 10 dB/grid

Horizontal scale: 50kHz/grid

Scan time: 0.2 sec/grid

3.Adjust the center frequency of the spectrum analyzer to video carrier frequency to be tested.

4.Adjust the input attenuation and reference level of the analyzer so that the carrier peak falls on the topmost scale line on the analyzer. This line is the reference line for the test.

5.Turn off the carrier to be tested. What is shown on the analyzer at this moment is the composite triple beat (CTB) and its difference from the reference level is the composite third order (CTO).

6.Adjust the center frequency of the analyzer to video carrier frequency to be tested plus 0.75MHz.

7.What is shown on the analyzer at this moment is the composite double beat (CDB) and its difference from the reference level is the composite second order (CSO).

8.Adjust the center frequency of the analyzer to video carrier frequency to be tested plus 1.25MHz.

9.What is shown on the analyzer at this moment is also CDB and its difference from the reference level is CSO.

10.The carrier composite beat ratio is the smallest of measurements from Steps 5, 7 and 9.

5.Test method for cross modulation ratio:

(1)Instruments required:

1.Continuous wave generator or multi-channel signal generator (capable of 100% synchronized square-wave modulation at 15734 ±20Hz)

2.Spectrum analyzer

3.Band-pass filter for the channel to be tested or adjustable band-pass filter (with bandwidthof1 to 6 MHz)

(2)Test procedure:

3.5 channels shall be selected for each examination point for systems with bandwidth smaller than 750MHz. For bandwidth greater than 750MHz, one additional channel shall be selected for every additional 100MHz. The bandwidth less than 100MHz is considered 100MHz. The channels selected for testing shall be distributed evenly across low, medium and high bands. The system’s cross modulation ratio fails to meet the Specifications if any channel selected for testing at any point fails to meet the criteria specified for the Specifications.

(3)Test steps:

1.See Figure 2 for test setup.

2.Adjust every carrier to the lowest level required by the system.

3.Modulate all carriers with 87.5% square wave except the channel to be tested.

4.Adjust the center frequency of the spectrum analyzer to the video carrier to be tested.

5.Adjust the analyzer to show±15kHz of sideband.

6.Measure and document the difference in amplitude between 15kHz sideband and center frequency.

7.The cross modulation is calculated by subtracting 10dB from the difference in amplitude.

6.Test method for carrier hum noise modulation ratio:

(1)Instruments required:

1.RF signal generator or television modulator capable of generating continuous waves, television converter.

2.RF level meter (with video output)

3.Low-pass filter (1kHz)

4.Spectrum analyzer

(2)Test procedure:

3.5 channels shall be selected for each examination point for systems with bandwidth smaller than 750MHz. For bandwidth greater than 750MHz, one additional channel shall be selected for every additional 100MHz. The bandwidth less than 100MHz is considered 100MHz. The channels selected for testing shall be distributed evenly across low, medium and high bands. The system’s carrier hum noise modulation ratio fails to meet the Specifications if any channel selected for testing at any point fails to meet the criteria specified for the Specifications.

(3)Test steps:

1.See Figure 2 for test setup.

2.Use the RF signal generator to input a continuous wave to be tested at the head end. Its level shall be the same as the system’s video carrier level.

3.Test with the spectrum analyzer.

7.Test method for carrier beat ratio:

(1)Instruments required:

1.Variable attenuator

2.Band-pass filter for the channel to be tested (bandwidth from 10 to 14 MHz)

3.Spectrum analyzer

(2)Test procedure:

3.5 channels shall be selected for each examination point for systems with bandwidth smaller than 750MHz. For bandwidth greater than 750MHz, one additional channel shall be selected for every additional 100MHz. The bandwidth less than 100MHz is considered 100MHz. The channels selected for testing shall be distributed evenly across low, medium and high bands. The system’s carrier beat ratio fails to meet the Specifications if any channel selected for testing at any point fails to meet the criteria specified for the Specifications.

(3)Test steps:

1.See Figure 2 for test setup.

2.Adjust the center frequency of the spectrum analyzer to the video carrier frequency to be tested.

3.Adjust the input attenuation and reference level of the analyzer so that the carrier peak-to-peak value falls on the topmost scale line of the analyzer. This line is the reference line.

4.Turn off the carrier to be tested. Adjust the resolution bandwidth and video bandwidth of the analyzer to show the peaks of all signals on screen.

5.Compare the signal values shown against the required value.

8.Test method for subscriber terminal isolation:

(1) Instruments required:

1.Signal generator

2.RF level meter

(2)Test procedure:

3.All channels of the system shall be tested. The system’s subscriber terminal isolation fails to meet the Specifications if any channel selected for testing at any point fails to meet the criteria specified for the Specifications.

(3)Test steps:

1.See Figure 3 for test setup.

2.Connect the output of signal generator directly to the RF level meter.

3.Adjust the frequency of the signal generator to the video carrier frequency to be tested.

4.Adjust the output level of the signal generator to 18dBμV.

5.Connect the output of signal generator and input of RF level meter to each of the test ports to test the subscriber terminal isolation. (The difference between the reading of RF level meter and 18dBμV is the subscriber terminal isolation.)

9.Test method for distribution network frequency response:

(1)Instruments required

1.Sweep frequency generator

2.Spectrum analyzer

(2)Test procedure: