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Broadcast Warehouse TX 150/300 Technical Manual

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Broadcast Warehouse
TX 150/300 FM BROADCAST TRANSMITTER
Technical manual
No part of this manual may be re-produced in any form without prior written permission from Broadcast Warehouse.
The information and specifications contained in this document is subject to change at any time without notice.
Copyright 2001 Broadcast Warehouse
For the latest contact information for Broadcast Warehouse please visit our website at,
www.broadcastwarehouse.com

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Summary of Contents for Broadcast Warehouse TX 150/300

  • Page 1 TX 150/300 FM BROADCAST TRANSMITTER Technical manual No part of this manual may be re-produced in any form without prior written permission from Broadcast Warehouse. The information and specifications contained in this document is subject to change at any time without notice.

  • Page 2: Table Of Contents

    CONTENTS Introduction TX FM Transmitter Safety Front And Rear Panels Control And Monitor LCD Installation And Setup Frequency Setup R.F. Power Setup Alarms RS232 Control & Monitoring 2.41 RS232 Interface board 2.42 Windows application 2.43 Terminal control Modes Of Operation 2.51 A guide to the jumpers 2.52...
  • Page 3 Introduction TX 150/300 FM TRANSMITTER The Broadcast Warehouse TX 150/300 is a high specification FM broadcast transmitter. Its broadband “no-tune” design allows 87.5-108 Mhz operation from internal direct reading rotary switches or the front panel LCD frequen- cy control system if enabled. Digital PWM techniques provide an easily adjustable and accurate automatic level controlled R.F.

  • Page 4: Introduction

    Introduction SAFETY MAINS VOLTAGE. This equipment operates from an AC power source of between 90 and 265 volts. There are hazardous voltages present internally. PLEASE OBSERVE CAUTION WITH THE COVER REMOVED. SWITCHED MODE POWER SUPPLY HAZARD Please note that the power supply units in this equipment is of the switched mode variety and have lethal voltages present internally.

  • Page 5: Front And Rear Panels

    Introduction FRONT AND REAR PANELS FUSE page 5 TX FM Transmitter technical manual...

  • Page 6: Control And Monitor Lcd

    Introduction CONTROL AND MONITOR LCD The front panel LCD graphics display has seven screens (shown below). These allow monitoring of the transmit- ter’s R.F., audio and other parameters and the adjustment (if internally allowed) of the transmitter’s power and fre- quency.

  • Page 7: Installation And Setup

    Installation and setup FREQUENCY SETUP The Frequency can be set on the transmitter in one of two ways: 1. From internal direct reading decimal switches on the main board 2. From the front panel LCD display and front panel buttons. Many radio regulatory bodies stipulate that the transmitters parameters including the frequency must not be easily changed from the front panel.

  • Page 8: Power Setup

    Installation and setup R.F. POWER SETUP The R.F. power output from the transmitter can be controlled by an analogue potentiometer (POT) or from the front panel LCD screen or a combination of both. ANALOGUE POWER CONTROL If the frequency is set internally with the dial switches you will not be able to adjust the power from the LCD screen.

  • Page 9: Alarms

    The RS232 interface provides the ability to reset the alarms. More info is found in the RS232 section of manual. Broadcast warehouse can also customise the alarm / fault software to meet the requirements of major broadcasters and networks. More information on this and other custom features can be obtained from our technical department.

  • Page 10: Rs232 Control & Monitoring

    9 way D-type COMPUTER socket.. The above item is an optional extra and is available from broadcast warehouse and it’s distributors 2.42 Windows application (TXCTRL.EXE) The latest version of TXCTRL.EXE can be downloaded from... http://www.broadcastwarehouse.com/downloads Installation...

  • Page 11: Terminal Control

    Installation and setup COM port you want to use and then click the Connect button. If the application is able to connect to the trans- TXCTRL when connected mitter then you will be presented with a screen similar to the one on the right. Once connected you should be able to view all the parameters of the transmitter as well as being able to mute the R.F., change the frequency, change the R.F.
  • Page 12 Installation and setup The frequency change key’s will perform an automatic screen refresh on there execution but the other keys will require a refresh command to be sent to the transmitter for you to visibly be able to see the effect of your com- mand.

  • Page 13: Modes Of Operation

    Installation and setup 2.5 MODES OF OPERATION The transmitter is fully configurable and can be set up to support various modes of operation. The mode of opera- tion is set by the configuration of the internal jumpers. This chapter provides a guide to the various jumpers, followed by a brief description of the main modes of opera- tion.
  • Page 14 Installation and setup There are altogether twelve jumpers on the board which can be set - at the time of installation - to establish the way the board operates. The board leaves the factory with default settings which should be suitable for most locations and requirements. Nevertheless, it is worth familiarizing yourself with all the options available, and checking that the settings are appro- priate, as part of the installation process.
  • Page 15 Installation and setup This option affects the character of the sound passing through the limiters inside the board. The sound can be either (a) processed to be competitively loud, with some sacrifice in fidelity (hard limiting, the Loud posi- tion) or (b) treated more gently, with high fidelity, but some loss in volume (soft limiting, the Pure position). It’s instructive to listen to and compare the options while passing a representative selection of typical pro- gramme material through the board.

  • Page 16: Multiplex / Broadband Input

    Installation and setup jumper 12, the ‘bridge’ link (see below). This jumper does not affect the mono/stereo status of externally- coded MPX inputs (J1 off). Jumper 12: Mono bridge The default position is OFF. When the board is operating in mono, the bridge should be set to ON. This ensures that when the board is operating in mono, no stereo information is broadcast, and that a mono drive to either left or right inputs, or a stereo input applied simultaneously to L and R inputs, will produce proper summed mono operation and no spurious 38KHz signals.
  • Page 17 Installation and setup Other configurations can be set by setting the jumpers in certain ways. For example: Mono with limiter off. We have illustrated what we feel to be the most popular options. JUMPERS. To suit application * Loopthrough mode The transmitter has been provided with a multiplex output socket to present the output of the internal audio stages to the outside world.

  • Page 18: Stereo With Limiters

    Installation and setup ADVANCED SETUP PROCEDURE The front panel LCD metering is accurate enough to set up the transmitter in the absence of external test equip- ment. If you have access to a modulation meter and RF power meter then substitute those for references to the relevant LCD display menu.
  • Page 19 Installation and setup 5. We should check that any offsets internal to the limiter are nulled out to keep distortion to a minimum. Connect a multimeter set to millivolts to testpoint TP1 which is located next to the right clipper jumper. You will also need an earth point for the meter.

  • Page 20: Stereo With Limiters Disabled

    Installation and setup 2.54 Stereo with internal limiters disabled. The limiter can be disabled internally if you do not require it. This effectively allows any audio input signals straight through to the stereo encoder unaltered. You may wish to disable the limiter when you have an external processor or limiter that may be of a higher performance than the internal limiter in this transmitter.

  • Page 21: Mono From Two Channels

    Installation and setup The transmitter should now have the total multiplex and the pilot setup at the correct level. All that is left to do is to set the input gain controls to suit your external equipment. 9. Set the limiter clippers J6 and J7 to OFF and set the filter clippers J10 and J11 to OFF. 10.

  • Page 22: Mono From One Channel

    Installation and setup 4. Set the internal limiter to OFF with jumper J8. Set the limiter clippers to ON with jumpers J6 and J7. Set the 15KHz filter clipper jumpers J10 and J11 to ON. Remove the pre-emphasis jumpers from J2 and J3 completely for now.

  • Page 23: Other Setup Considerations

    Installation and setup You can provide one audio feed to the transmitter via the left balanced input. This has the advantage of supplying two exact audio signals to the stereo encoder section that will in turn cancel the stereo subcarrier leaving only a pure mono signal with content falling to zero above 15KHz.
  • Page 24 Installation and setup The rear panel BNC sockets provide an easy interface to the multiplex path. You can insert an external piece of equipment between the multiplex output of the internal stereo encoder and the modulator section. To connect an external piece of equipment consult the external equipments documentation. It should be as easy as configuring the transmitter as per normal and then simply setting the internal Loopthrough jumper to OFF and taking the multiplex output to the input of the external equipment and the output of the external equipment back into the multiplex input socket.

  • Page 25: Technical Data

    Technical data SPECIFICATIONS Power 20-175 (TX150) 30-300 (TX300) Connector N type 50 ohm Harmonics better than 65 dbc Spurious < -75 dbc Frequency range 87.5 - 108 MHz Frequency steps 100KHz from LCD or 12.5 KHz from internal switches Frequency selection Internal switches or LCD system Frequency control type Dual speed Phase locked loop...

  • Page 26: Circuit Description

    Technical data CIRCUIT DESCRIPTION The transmitter consists of three circuit boards, two power supply modules and the associated wiring and connec- tors. Both of the power supplies are fully approved bought in modules and won’t be discussed electrically except for the connections to the other boards where appropriate. The three PCB’s previously mentioned are the combo board, the power amplifier board and the control / LCD board.
  • Page 27 Technical data allel with R4(R33) . This has the effect of a more “commercial loud sound” when in loud mode compared to a more true to the original sound when in clarity mode due to less clipping taking place. VR3(VR4) is connected across the inputs of the transconductance amplifier and provide offset adjustment to null any distortions intro- duced by offsets inherent in the op-amps Stereo encoder description...
  • Page 28 Technical data the PLL locked condition. The front panel control system will also display the locked condition when in the fre- quency display screen. Audio is fed into the modulation input of the exciter from external multiplex input connector CON2 which is a BNC type or from the internal stereo encoder section by having jumper J1 set to loopthrough.
  • Page 29 Technical data LCD CONTROL BOARD The LCD control board is the heart of the transmitter. The board contains an eight bit microcontroller, LCD display, a voltage regulator and a dual op-amp together with a few passive components. CON1 provides a 10 way interface to the power amplifier board and its sensors. Some of the connections of CON1 are routed around to the power supply modules.
  • Page 30 Technical data B of the op-amp. page 30 TX FM Transmitter technical manual...

  • Page 31: Block Diagram

    Technical data BLOCK DIAGRAM page 31 TX FM Transmitter technical manual...
  • Page 32 Technical data WIRING AND INTERNAL OVERVIEW page 32 TX FM Transmitter technical manual...
  • Page 33 Technical data 3.51 LCD control board page 33 TX FM Transmitter technical manual...
  • Page 34 Technical data 3.52 Power amplifier board page 34 TX FM Transmitter technical manual...

  • Page 35: Limiter Section

    Technical data 3.531Combo board, limiter section page 35 TX FM Transmitter technical manual...
  • Page 36 Technical data 3.532 Combo board, stereo encoder section page 36 TX FM Transmitter technical manual...
  • Page 37 Technical data 3.533 Combo board, PLL exciter section page 37 TX FM Transmitter technical manual...

  • Page 38: Parts List

    Technical data PARTS LIST 3.62 Power amplifier board 3.61 LCD control board RESISTORS RESISTORS 1K8-3K6 (sot) 1/4 Watt Metal Oxide 1/8 Watt Carbon Film 1/4 Watt Metal Oxide 1/8 Watt Carbon Film 1/4 Watt Metal Oxide 820R 1/8 Watt Carbon Film 1 WATT 2512 SMD 390R 1/8 Watt Carbon Film...
  • Page 39 Technical data 100N Monolithic Ceramic 2.5 pitch 27pF Ceramic Plate 2.5 pitch (680) 100N Monolithic Ceramic 2.5 pitch 56pF Ceramic Plate 2.5 pitch (680) 100N Monolithic Ceramic 2.5 pitch 82pF Ceramic Plate 2.5 pitch (680) 100N Monolithic Ceramic 2.5 pitch Gen.
  • Page 40 Technical data 470uf 16V Radial Electrolytic 1/8 Watt Carbon Film 470uf 16V Radial Electrolytic 330K 1/8 Watt Carbon Film 2.2uF 16V Miniature Radial Electrolytic 330R 1/8 Watt Carbon Film 100n Y5V Monolithic Ceramic 2.5 pitch 330R 1/8 Watt Carbon Film 10uF 35V Miniature Radial Electrolytic 1/8 Watt Carbon Film...
  • Page 41 Technical data 470K 1/4 Watt Metal Oxide 470K 1/4 Watt Metal Oxide 1/4 Watt Metal Oxide 1/4 Watt Metal Oxide 1/4 Watt Metal Oxide 470R 1/4 Watt Metal Oxide 1/4 Watt Metal Oxide 1/4 Watt Metal Oxide 1/4 Watt Metal Oxide 1/4 Watt Metal Oxide 1/4 Watt Metal Oxide 1/4 Watt Metal Oxide...

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