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TX25/50 FM Broadcast Transmitter
Technical manual
No part of this manual may be re-produced in any form without prior written permission from BW Broadcast.
The information and specifications contained in this document is subject to change at any time without notice.
Copyright 2009 BW Broadcast
www.bwbroadcast.com
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Table of Contents
Related Manuals for BW Broadcast TX25
Summary of Contents for BW Broadcast TX25
- Page 1 TX25/50 FM Broadcast Transmitter Technical manual No part of this manual may be re-produced in any form without prior written permission from BW Broadcast. The information and specifications contained in this document is subject to change at any time without notice.
- Page 2 WARNING This transmitter should never be operated without a suitable antenna or test dum- my load! Failure to observe this requirement may result in damage to the transmit- ter that is not covered by the warranty. IMPORTANT This transmitter has been shipped with the internal stereo generator enabled. The internal jumper J1 (MPX loop-through) is set to ON.
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Page 3: Table Of Contents
Limiter section .512 Coder section .51 Exciter section .52 LCD control section .5 Power amplifier section Parts List .61 Combo board parts list .62 LCD control board parts list .6 Power amplifier board parts list Page BW Broadcast technical manual... - Page 4 Introduction TX 25/50 FM TRANSMITTER The BW Broadcast TX 25/50 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 frequency con- trol system if enabled. Digital PWM techniques provide an easily adjustable and accurate automatic level control- led R.F.
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Page 5: Introduction
SCH and has been issued with WEE/FA0268RX as its unique producer ID by the appro- priate environment agency. BW Broadcast Ltd full comply with it explicit responsibilities, subject to WEEE Collections Policy outlined in their General Terms and conditions of Sale, when it sells Electrical and Electronic Equipment (EEE) to B2B customers in the UK and EU. - Page 6 If necessary adjust the audio input level trimmers on the back of the transmitter. That finishes the set-up. A much more detailed explanation is available in the appropriate sections of this manual as well as additional options. You should read through it! Page 6 BW Broadcast technical manual...
- Page 7 IN OUT RF OUT That finishes the set-up. A much more detailed explanation is available in the appropriate sections of this manual as well as additional options. You should read through it! BW Broadcast Transmitter Page 7 BW Broadcast technical manual...
- Page 8 That finishes the set-up. A much more detailed explanation is available in the appropriate sections of this manual as well as additional options. You should read through it! IN OUT IN OUT RF OUT RF OUT BW Broadcast BW Broadcast Transmitter Transmitter Page 8 BW Broadcast technical manual...
- Page 9 Check the documentation that came with your RDS encoder on how to set/check the proper RDS injec- tion level. That finishes the set-up. A much more detailed explanation is available in the appropriate sections of this manual as well as additional options. You should read through it! Page 9 BW Broadcast technical manual...
- Page 10 Check the documentation that came with your RDS encoder on how to set/check the proper RDS injec- tion level. That finishes the set-up. A much more detailed explanation is available in the appropriate sections of this manual as well as additional options. You should read through it! Page 10 BW Broadcast technical manual...
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Page 11: Front And Rear Panels
Introduction FRONT AND REAR PANELS Page 11 BW Broadcast technical manual... -
Page 12: Control And Monitor Lcd
The power amplifier voltage will vary depending on set output power and the presence of any fault conditions which also cut the voltage back and with it the R.F. output. Page 12 BW Broadcast technical manual... -
Page 13: Installation And Setup
The LCD readout will only display frequencies in 100Khz steps. Any frequency offsets derived from the internal 12.5kHz offset switch will not show on the LCD. Consult a frequency counter if using offsets. Page 1 BW Broadcast technical manual... -
Page 14: Power Setup
The windows application has a button that can toggle the RF output of the trans- mitter. Please consult the RS232 section of this manual for more information on controlling the transmitter remotely. TRANSMITTER Page 14 BW Broadcast technical manual... -
Page 15: Alarms
More info is found in the following pages of the manual. BW Broadcast can also customise the alarm / fault software to meet the requirements of major broadcast- ers and networks or supply N+1 solutions. More information on this and other custom features can be obtained from our technical department. -
Page 16: Windows Remote Control Application
The transmitter is internally set to communicate at 9600 bps, no parity with 1 stop bit and hardware flow control. This is commonly known as 9600 8N1. If your using Windows then you can use the pre-bundled terminal program “Hyper-terminal”. This is located in the Programs -> Accessories -> Communications folder accessible Page 16 BW Broadcast technical manual... - Page 17 'Enter’ key a few Reset alarms (all to 0 / off) times in succession. Mute R.F. Unmute R.F. ENTER Refresh screen Page 17 BW Broadcast technical manual...
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Page 18: Modes Of Operation
Mono from left Right pre-emphasis Right Loud/Clarity VR3-4 Limiter offset trim Left Pre-emphasis Left Loud/Clarity Left Lim. Clipper Right Lim. Clipper Limiter On/Off Left filter Clipper Right filter Clipper Pilot level control Pilot On/Off (stereo) Page 18 BW Broadcast technical manual... - Page 19 These jumpers do not affect the operation of the board when external MPX is used with Jumper 1 off. Jumpers 4 and 5: Limiter loud/pure The default position is ‘Loud’ (hard limiting). Page 19 BW Broadcast technical manual...
- Page 20 ‘stereo’ beacon to light on a receiver. If no 19kHz tone is received, the receiver will operate in mono. It will not decode any L-R information modulated on the 8 kHz subcarrier, even when it is still present. Page 20 BW Broadcast technical manual...
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Page 21: Multiplex / Broadband Input
See loopthrough mode below * JUMPERS. J1 (ON), J2- (50 or 75), J4-5 (LOUD or CLARITY), J6-7 (ON), J8 (ON), J9-10 (ON), J11 (MO), J12 (ON) Page 21 BW Broadcast technical manual... - Page 22 This is to stop the internal stereo encoder’s multiplex output signal from being fed to the exciter section internally. More information on loopthrough setup is provided at the end of the advanced setup procedure section Page 22 BW Broadcast technical manual...
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Page 23: Stereo With Limiters
These settings will allow any audio straight through the limiter and into the limiter clippers that set our final peak level. 5. We should check that any offsets internal to the limiter are nulled out to keep distortion to a minimum. Connect Page 2 BW Broadcast technical manual... - Page 24 1 kHz or so of this figure. If your deviation does exceed 75 kHz then adjust the back panel multiplex control to keep your maximum deviation at 75 kHz. Page 24 BW Broadcast technical manual...
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Page 25: Stereo With Limiters Disabled
9. Set the limiter clippers J6 and J7 to OFF and set the filter clippers J10 and J11 to OFF. 10. Connect a 400 Hz tone at your desired level to the left channel and adjust the left channel gain control on the Page 25 BW Broadcast technical manual... -
Page 26: Mono From Two Channels
J12 is set to the OFF position. Disable the stereo pilot by setting jumper J11 to MONO. Set the limiter mode jump- er J4 and J5 to LOUD. These settings will allow any audio straight through the limiter and into the limiter clippers that set our final peak level. Page 26 BW Broadcast technical manual... -
Page 27: Mono From One Channel
1. Follow the advanced setup procedure for the ‘mono from two independent channels’ mode completely as if you would be using that mode. Set all the jumpers and levels correctly as if you would be using that mode. Both Page 27 BW Broadcast technical manual... -
Page 28: Other Setup Considerations
If the external equipment is not unity gain you may have to readjust the multiplex input gain slightly to take account for any gain differences. Most loopthrough designed equipment is unity gain to make setup and use as simple as possible. Page 28 BW Broadcast technical manual... - Page 29 VC2. LCD SYSTEM METERING ACCURACY DISPLAY Measurement Accuracy POWER SUPPLY Volts +/-1 Volt TEMPERATURE Degrees Centigrade +/-1 Degree PEAK DEVIATION +/-1 kHz LIMITER GAIN REDUCTION Decibels +/-1 dB RF POWER Watts Page 29 BW Broadcast technical manual...
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Page 30: Technical Data
Technical data SPECIFICATIONS Power W - 25W (TX25), 5W - 50W (TX50) Connector N-type 50 Ohm Harmonics better than 88 dBc Spurious < -90 dBc Frequency range 87.5 - 108 MHz Frequency steps 100 kHz from LCD or 12.5 kHz from internal switches... -
Page 31: Circuit Description
The amount of clipping can be con- trolled by J4(J5). These provide more drive to the gain control op-amps by putting resistor R5(R69) in parallel Page 1 BW Broadcast technical manual... - Page 32 PLL chip. The microcontroller can also use this information to switch off transistor T6 with open collector configured T11 which mutes the RF output when the transmitter is out of lock. LED5 provides visual indi- Page 2 BW Broadcast technical manual...
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Page 33: Lcd Control Board
8 MHz signal for the clock of the microcontroller. R12 and R1 provide pull downs for correct opera- tion of the internal processor communications channel. C12 provides supply decoupling for the microcontroller and VR1 sets the contrast of the LCD display. Page BW Broadcast technical manual... - Page 34 R21 and CON1. R22 and C15 provide supply decoupling for the op-amp. C14,15,16,17,18 provide further decoupling and feedback for the power control feedback loop formed around side B of the op-amp. Page 4 BW Broadcast technical manual...
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Page 35: Power Amplifier Board
LCD control board and the combo board, and last but not least the PA power modules control line which controls it’s output voltage. This control signal is derived from the LCD / control board and is wired through the power amplifier PCB and out through CON to the power supply module. Page 5 BW Broadcast technical manual... -
Page 36: Block Diagram
Technical data BLOCK DIAGRAM Page 6 BW Broadcast technical manual... - Page 37 Technical data WIRING AND INTERNAL OVERVIEW Page 7 BW Broadcast technical manual...
- Page 38 Technical data 3.51 COMBO BOARD SCHEMATICS 3.511 Limiter section Page 8 BW Broadcast technical manual...
- Page 39 Technical data 3.512 Stereo encoder section Page 9 BW Broadcast technical manual...
- Page 40 Technical data 3.513 PLL exciter section RS22 / CONTROL O / C SIGNALS TTL SIGS RF MUTE Page 40 BW Broadcast technical manual...
- Page 41 Technical data 3.52 LCD CONTROL BOARD Page 41 BW Broadcast technical manual...
- Page 42 Technical data 3.53 PA BOARD SCHEMATICS Page 42 BW Broadcast technical manual...
- Page 43 Radial Inductor (Toko 10RB) #181LY-472J MC100 075 Screened Variable Inductor (MC120) #E526HNA-100075 MC100 112 Screened Variable Inductor (MC120) - #E526HNA-100112 MC120 073 Screened Variable Inductor - (MC120) #E526HNA-100073 0.33uH Axial Inductor Body 7mm, Dia 2.8mm Page 4 BW Broadcast technical manual...
- Page 44 1/4 Watt Metal Oxide - Tolerance +- 1% R28, R132 1/4 Watt Metal Oxide - Tolerance +- 1% 1/4 Watt Metal Oxide - Tolerance +- 1% 1/4 Watt Metal Oxide - Tolerance +- 1% Page 44 BW Broadcast technical manual...
- Page 45 1A TO220 5V Linear Regulator T1,T2 BC327 (C3271) BC327-16 TO92 50V PNP GP TRANSIST T3,T4,T5,T6 MPSH10 High Speed Switching Transistor ZVN4306A Zetec Transistor 2N4427 High Speed Switching Transistor APT T8,T9,T10 BC337 (C3371) C337-16 TO92 50V NPN GP TRANS Page 45 BW Broadcast technical manual...
- Page 46 LCD Screen Blue LCD Display 40-Pin 40 Pin IC Socket IC2,IC3 8-Pin 8-Pin IC Socket Panel Buttons Molded Cap for Switch (NOT FITTED) Con1 10-Way 10 Way Boxed Header Con2 16-Way 16 Way Boxed Header Page 46 BW Broadcast technical manual...
- Page 47 22pF 2.5mm Pitch Ceramic Disc 18pF 2.5mm Pitch Ceramic Disc 12pF 2.5mm Pitch Ceramic Disc 15pF 2.5mm Pitch Ceramic Disc 5mm Pitch Ceramic Disc NOT USED 2.5mm Pitch Ceramic Disc C50,C53,C54 High Freq Version Page 47 BW Broadcast technical manual...
- Page 48 CON5 CONN-H2 USED WITH CON4 -N/A CON6 CONN-DIL10-IDC 10-Way RA IDC Header CON7 COAXSOCKET MCX PCB Connector REG1 7818CT 18V Regulator REG2 7812CT High Freq Version RFT1 T37-8/90 VSWR Ferrite Red/Yellow LM335Z Thermal Sensor Page 48 BW Broadcast technical manual...
- Page 49 www.bwbroadcast.com...