UBS Axcera LU100AT 100-Watt UHF Transmitter User Manual

UBS-Axcera 100-Watt UHF Transmitter 377400

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Chapter 4

UHF Analog Driver/Transmitter    Chapter 4, Circuit Descriptions LX Series, Rev. 0  4-1 Chapter 4 Circuit Descriptions  4.1 (A2) Modulator Module (1301929; Appendix B)  NOTE: Not used in a translator system.  4.1.1 Analog Modulator Board (1301797; Appendix B)  The board takes the audio and video inputs and produces a modulated visual IF + aural IF output.  Main Audio and Aural IF portion of the board  The analog modulator board takes each of the three possible audio inputs and provides a single audio output.  4.1.1.1 MONO, Balanced Audio Input  The first of the three possible baseband inputs to the board is a 600-Ω, balanced-audio input (0 to +10 dBm) that enters through jack J41A, pins 10A (+), 12A (GND), and 11A (-), and is buffered by U11A and U11B. Diodes CR9, CR10, CR12 and CR13 protect the input to U11A and U11B if an excessive signal level is present on the input. The outputs of U11A and U1B are applied to differential amplifier U11C. U11C eliminates any common mode signals (hum) on its input leads.  A pre-emphasis of 75 ms is provided by R97, C44, and R98 and can be eliminated by removing jumper W6 on J22.  The signal is then applied to amplifier U11D whose gain is controlled by jumper W7 on J23.  Jumper W7 on jack J23 is positioned according to the input level of the audio signal (0 or +10 dBm). If the input level is approximately 0 dBm, the mini-jumper should be in the high gain position between pins 1 and 2 of jack J23. If the input level is approximately +10 dBm, the mini-jumper should be in low gain position between pins 2 and 3 of jack J23. The balanced audio is then connected to buffer amplifier U12A whose input level is determined by the setting of the MONO, balanced audio gain pot R110, accessed through the front panel.  The output of the amplifier stage is wired to the summing point at U13C, pin 9.  4.1.1.2 STEREO, Composite Audio Input  The second possible audio input to the board is the composite audio (stereo) input that connects to the board at J41A Pin 14A (+) and J41A Pin 13A (-).  NOTE: For the transmitter to operate using the composite audio input the Jumper W1 on J4 must be between Pins 2 and 3, the Jumper W2 on J6 must be between Pins 2 and 3 and the Jumper W4 on J5 must be between Pins 1 and 2. These jumpers connect the composite audio to the rest of the board.  Jumper W14 on jack J26 provides a 75Ω-input impedance when the jumper is between pins 1 and 2 and a high impedance when it is between pins 2 and 3. Diodes CR17, CR18, CR20 and CR21 protect the input stages of U14A and U14B if an excessive signal level is applied to the board. The outputs of U14A and U14B are applied to differential amplifier U13A, which eliminates common mode signals (hum) on its input leads. The composite input signal is then applied to amplifier U13B; whose gain is controlled by the STEREO, composite audio gain pot R132, accessed through the front panel. The composite audio signal is then connected to the summing point at U13C, pin 9.  4.1.1.3 SAP/PRO, Subcarrier Audio Input  The third possible input to the board is the SAP/PRO, SCA audio input at J41A pin 16A(+) and 17A(-). The SCA input has an input matching impedance of 75Ω that can be eliminated by removing jumper W15 from pins 1 and 2 of J28. The SCA input is bandpass filtered by C73, C74, R145, C78, C79, and R146 and is fed to buffer
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Document ID377407
Application IDQC713b4X7M+PFd56CshcQg==
Document DescriptionChapter 4
Short Term ConfidentialNo
Permanent ConfidentialNo
SupercedeNo
Document TypeUser Manual
Display FormatMicrosoft Word - pdf
Filesize24.61kB (307619 bits)
Date Submitted2003-12-02 00:00:00
Date Available2004-01-28 00:00:00
Creation Date2003-12-03 07:31:33
Producing SoftwareAcrobat Distiller 5.0.5 (Windows)
Document Lastmod2003-12-03 07:31:33
Document TitleMicrosoft Word - 377407.DOC
Document CreatorPScript5.dll Version 5.2
Document Author: fcc
FCC ID Filing: OUSLU100AT

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