Satellite Link Connection with C6M-II-SE

Transcription

1 3-8 Installation Satellite Link Connection with C6M-II-SE Figure 3-5 shows the connection between the C6R-VCII satellite receiver and the C6M-II with the Stereo Encoder option installed. Figure 3-5 Satellite link connection with stereo encoder

2 Installation 3-9 Video Scrambling The C6M-II can be connected to a General Instrument Modulating Video Processor (MVP II) for video and audio scrambling as displayed in Figure 3-6. Note: General Instrument recommends using the C6U dual upconverter to interface with the MVP II. Figure 3-6 MVP II / C6M-II IF interfacing When connecting the MVP II to the C6M-II, use the IF set up in the MVP II Installation Manual and the following steps for connecting the C6M-II: Verify that the MVP II is in standby mode. Select video A input (INPT VA) on the Main menu and activate IF AGC on the Option menu display Tune to a test channel. Ensure that appropriate test equipment is connected to RF OUT on the rear panel. Measure the RF output and check for the following conditions: If the RF video carrier output is less than 60 dbmv, adjust the RF output on the C6M-II for 60 dbmv. Deactivate the IF AGC on the Option menu display and select auxiliary IF (INPT AUX) on the Main menu as the input. When sync suppression scrambling is used, IF AGC must be turned off in the C6M-II Monitor the test equipment to verify 60 dbmv is still present at the RF output.

3 3-10 Installation If the RF level is not 60 dbmv, the COMP IF control on the MVP II can be adjusted. Do not exceed 32 dbmv at the IF output of the MVP II. If the RF level is still not 60 dbmv, use manual IF gain control on the Option menu to set RF level. Do not use RF level control to set the RF output level at this stage. CW Output The CW output is a MHz carrier signal that can be used with the MVP II when it is necessary to insert a coherent IF carrier for phase-locked upconversions. Figure 3-7 illustrates the connection of the C6M-II and the MVP II in a phase-locked upconversion. Figure 3-7 MVP II / C6M-II interfacing using the CW output

4 Installation 3-11 Stereo IF Interfacing The CMTS stereo encoder can be used with the C6M-II as shown in Figure 3-7 if the MOB option board is installed. To activate the subcarrier input, select the Input selection menu item INPT SUB on the Main menu or short the subcarrier terminal on the rear panel to the ground terminal. Use the level adjustment on the CMTS front panel to adjust the RF output sound carrier level. Figure 3-8 C6M-II / CMTS IF interfacing

5 3-12 Installation Composite Baseband Interfacing If the MOB option board is installed, an external composite baseband can be accepted. To use the external composite baseband input, connect the unit as shown in Figure 3-9. To activate, select the Input selection menu item INPT CMP on the Main menu or short the subcarrier terminal on the rear panel to the ground terminal. Menu selection is recommended. The short on the rear panel is not required if the INPT CMP option is selected via the menu. Figure 3-9 External composite baseband connection

6 Installation 3-13 CMTS / MVP II / C6M-II Connections Figure 3-10 shows the connections between the CMTS, MVP II and C6M-II. Figure 3-10 C6M-II / MVP II / CMTS interfacing

7 3-14 Installation C6R-VCII / CMTS / MVP II / C6M-II Connections Figure 3-11 shows the connections between the C6R-VCII, CMTS, MVP II and C6M-II. Figure 3-11 C6R-VCII / CMTS / MVP II / C6M-II connections

8 Section 4 System Block Diagrams This section describes the operation of the C6M-II through a series of block diagrams. The text is keyed to letters on the block diagrams. Video to IF Modulation System Figure 4-1 Video to IF modulation system A B C D E F G H If the modulator option board is installed, baseband video input switching is available. The video switch includes a Video A level sensor which automatically switches to Video B when the Video A signal level is low or absent. Audio input switching follows the video input selection. A rear panel connection provides external control. Video AGC is provided with the modulator option board for use with varying video signal levels and when switching between video sources at different levels. The video system is applied to a dc clamp circuit. The dc clamp can be disabled through the menu. The clamped signal is applied to a variable gain stage to permit depth of modulation adjustment. Video modulation is controlled through the video modulation entry on the main menu. A dual diode bridge circuit provides amplitude modulation. The modulated IF output is buffered and then applied to an all-pass delay equalizer which corrects the total group delay response error generated by the C6M-II system. The signal is bandpass filtered to remove unwanted frequencies at the PIF OUT connector on the rear panel. The unmodulated MHz carrier is generated by a phase-locked loop which locks a voltage controlled oscillator to an internal 2 MHz reference.

9 4-2 System Block Diagrams Audio to IF Modulation System Figure 4-2 Audio to IF modulation system A B C D E F G H Left and right audio signals are encoded per BTSC standards when the stereo encoder option is installed. If the modulator option board is installed, audio switching is provided. The audio input will follow the switched video input. The audio input range is selected from the Audio range (AUDR) entry on the Audio menu. Either the low range (AUDR LOW) which is 10 to +10 dbm, or the high range (AUDR HI) which is +5 to +25 dbm, may be selected. The audio input impedance is selected from the Audio impedance (AUDZ) entry on the Audio menu. Either low impedance (AUDZ LOW) which is 600 Ohms balanced, or high impedance (AUDZ HI) which is 15 kohms, may be selected. A variable gain stage sets the FM deviation to the required ±25 khz. This can be adjusted through the Audio deviation entry on the Main menu. An optional AGC capability is provided for situations involving an unstable audio source or switching between audio sources of different levels. This capability is enabled through the Audio AGC entry on the Audio menu. The standard broadcast television pre-emphasis can be disabled. Frequency modulation is accomplished by applying the processed audio signal to a 9.0 MHz voltage controlled oscillator (VCO). The center frequency of the sound carrier is precisely maintained by a phase-locked loop with an internal 2.0 MHz reference. The audio VCO s frequency is divided by two to produce the standard 4.5 MHz aural subcarrier

10 System Block Diagrams 4-3 frequency. I J K An optional external 4.5 MHz input switch is furnished to utilize a 4.5 MHz audio source. The subcarrier is mixed with the unmodulated MHz signal to create the MHz sound IF frequency. The sound IF carrier is bandpass filtered and applied to an amplifier whose gain is controlled by the A/V separation entry on the Main menu. This control sets the desired picture/sound carrier level ratio.

11 4-4 System Block Diagrams IF Switching and AGC System Figure 4-3 IF switching and AGC system A B C D E F G H I J The picture IF signal input is taken from the rear panel connectors. This signal is amplified to compensate for the loss of the surface acoustic wave (SAW) filter that follows. This filter generates the required television vestigial sideband response shape and eliminates unwanted frequencies. The sound IF signal input is taken from the rear panel connectors. A SAW bandpass filter removes unwanted frequencies. The filtered IF signals are combined to produce a composite IF signal. The signal is split and buffered. One of the signals is a composite IF output while the other is fed to a two-input IF relay switch. When not in use, the composite IF output should be terminated with 75 Ohms. The second input to the relay is normally from the AUX-IF input connector. After IF switching operations, the signal is applied to the Automatic IF Level Control (ALC) subsystem. This circuit assures constant input level to the output converter system when switching between IF signal sources that do not have equal level. The ALC function can be disabled when required for processing non-standard signals. The composite IF signal is buffered and filtered to remove any spurious signals and delivered to the IF-to-channel converter system input. A sample of that signal is provided at a front panel test point at 0 dbmv. With the option package installed, an additional relay is provided. The switch takes its two inputs from the rear panel AUX-IF and PRGM-IF inputs and delivers its output to the second input of the first relay switch.

12 System Block Diagrams 4-5 IF to Channel Converter System Figure 4-4 IF to channel converter system A B C D E F G H The IF input signal is applied to the first mixer. The local oscillator signal for the first mixer is generated by a voltage-controlled oscillator that is PLL controlled. The PLL frequency is programmed by the microprocessor to accommodate the selected channel plan or frequency setting. The local oscillator mixes with the IF input to produce the high IF which is then bandpass filtered and amplified. The high IF is applied to the second mixer. The circuit for the second local oscillator must be tunable over a 1000 MHz range to produce RF output picture carrier frequencies. The microprocessor programs the second LO PLL according to the channel or frequency setting. The channel frequency output signal from the second mixer is applied to a variable loss PIN attenuator. The circuit s loss is controlled by the RF output level entry on the Main menu. This permits trimming of the combined headend system carrier level for each channel. The signal is applied to the output bandpass filter bank. The appropriate filter is selected based on the selected channel number. The filter system minimizes the broadband output noise and allows unlimited broadband combining without need for external filters. The system maintains a combined headend carrier-to-noise ratio of 60 db. The RF output signal is supplied to the rear panel while a sample at 20 db below actual is brought to a front panel connector for monitoring the final output signal. The RF signal is amplified by a wideband low distortion amplifier module to provide the 60 dbmv specified picture carrier output level.

13 Appendix A Specifications RF Output Channels Frequency Range Frequency Accuracy Output Level Recommended operating range Spurious Output Return Loss Sound Carrier Level (adjustable) C/N Ratio (normalized to 4 MHz) In-band Adjacent Channel Wideband 2 to 161 (HRC, IRC, STD, EIA frequency plans or 12.5 khz steps) 50 to 1000 MHz ±5 khz maximum, ±500 Hz typical +60 dbmv minimum 57 to 61 dbmv 60 dbc 60 dbmv (50 to 1000 MHz) with sound carrier at 15 dbc 14 db minimum within channel (50 to 750 MHz) 13 db minimum within channel (750 to 1000 MHz) 10 to 20 db relative to video carrier 68.0 db minimum, 70.0 db typical 72.0 db minimum, 74.0 db typical 75.5 db minimum, 76.0 db typical IF Picture IF Output Frequency Picture IF Output Level Sound IF Output Frequency Sound IF Output Level CW IF Output Frequency CW IF Output Level Composite IF Output (picture IF level) MHz % modulation MHz 15 to 25 dbmv MHz 50 dbmv ±5 db 30 dbmv ±1 87.5% modulation Video

14 A-2 Specifications Standard Baseband Input Encoded Video Input Level Video Input Impedance Video Input Return Loss K Factor S/N Ratio (lum. weighted) Chroma Delay, relative to standard precorrection Frequency Response Differential Gain Differential Phase Tilt 0.5 to 2.0 Vp-p for 87.5% modulation 1.0 Vp-p for 87.5% modulation 75 Ohms 30 db minimum 2% maximum 64 db minimum ±50 nsec ±0.5 db from 0 to 4.1 MHz 87.5% modulation 1.0 degree p-p 87.5% modulation 1% maximum Audio Input Level Range Low High Input Impedance Low High Frequency Response Preemphasis Harmonic Distortion Hum and Noise Subcarrier Frequency Subcarrier Input Level 10 to +10 dbm, Z 0 = 600 Ohm +5 to +25 dbm, Z 0 = 600 Ohm 600 Ohms balanced 15 kohms minimum ±1.0 db from 30 Hz to 15 khz 75 µsec, defeatable 1% maximum from 30 Hz to 15 khz at ±25 khz 60 dbc maximum with ±25 khz 4.5 MHz ±500 Hz +35 to 45 dbmv General ac Voltage Requirements Power Requirements Operating Temperature Weight Dimensions 100 to 240 Vrms, 50 to 60 Hz 40 watts maximum 0 to 50 C 13.5 lbs maximum 19 W x 1.75 H x 17.5 D

15 Appendix B Frequency Plan GI Channel Number Picture Carrier Frequency (MHz) EIA Channel Historical Reference HRC IRC Standard EIA A A A B C D E F G H I J K L M N

16 B-2 Frequency Plan GI Channel Number Picture Carrier Frequency (MHz) EIA Channel Historical Reference HRC IRC Standard EIA O P Q R S T U V W X Y Z DD EE FF GG HH II JJ KK LL MM NN OO PP QQ A A-4

17 Frequency Plan B-3 GI Channel Number Picture Carrier Frequency (MHz) EIA Channel Historical Reference HRC IRC Standard EIA A A A RR SS TT UU VV WW XX YY ZZ

18 B-4 Frequency Plan GI Channel Number Picture Carrier Frequency (MHz) EIA Channel Historical Reference HRC IRC Standard EIA

19 Frequency Plan B-5 GI Channel Number Picture Carrier Frequency (MHz) EIA Channel Historical Reference HRC IRC Standard EIA

20 B-6 Frequency Plan GI Channel Number Picture Carrier Frequency (MHz) EIA Channel Historical Reference HRC IRC Standard EIA

21 Appendix C Changing a Menu Item The following example illustrates how to change the frequency. Display the frequency on the Main menu as described in Section 2, Overview. The illustration below shows the frequency Press the right arrow key. In this case, the digit 3 flashes as shown below. Press the up arrow key. The digit 4 appears and flashes as shown below. If this is the change you want, press the ENT key to implement the change. If you decide not to make the change, do not press ENT. The frequency will return to the previous value after a short delay.

22 C-2 Changing a Menu Item If you wish to return to the previous value immediately, press the left arrow key until the previous value appears. In this case the left arrow key is pressed three times, and, as shown below, the 0 flashes, the 5 flashes, and then the previous value appears. A summary: To reach any item in a menu To get into a submenu (e.g., Option) To get out of a submenu To change a menu item Use the up or down arrow key (menu wraps vertically). Use the right arrow key. Use the left arrow key. Use the right arrow key to cause the item to flash. Use the up or down arrow key until the desired value or function is reached. Press the ENT key to implement a change. Use the left arrow key to exit the menu. If no change is made, the value reverts to the previous setting.

23 Appendix D Signal Priority Chart

24 D-2 Signal Priority Chart

25 Signal Priority Chart D-3

26 D-4 Signal Priority Chart

27 Signal Priority Chart D-5

28 Appendix E Application Notes C6-LPF600 This application note is to assist you in the operation of the C6M in headends operating above 600 MHz. Summary The C6M incorporates a dual high IF conversion technique that minimizes spurious and distortion products within the 50 to 600 MHz operating bandwidth of the C6M. The high IF local oscillator, which is used to downconvert the high IF to the desired output RF carriers, operates above 600 MHz. This local oscillator frequency may be present at the C6M RF output and may cause interference with analog and digital channels, or data carriers operating above 600 MHz. To minimize this potential problem, install a C6-LPF600. The C6-LPF600 is a high performance, low-pass filter (10 to 600 MHz) that may be used to attenuate spurious carriers occurring at 600 MHz and above frequencies. The specifications on this filter are included with this application note. Discussion The C6-LPF600 (GI Part No ) is installed either at the RF output of the C6M, or may be installed at the C6M RF combined output before the insertion of channels operating above 600 MHz. Typical installations with the C6M and the C6M-II are displayed below. Figure E-1 Typical installations of C6-LPF600

29 E-2 Application Notes Specifications Passband Stopband Bandwidth 10 to 600 MHz 600 to 1000 MHz Insertion Loss 2.0 db maximum 40 db 673 MHz Return Loss 14 db minimum N/A

30 General Instrument Corporation GI Communications Division Printed in U.S.A , 3/97