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Broadcast Warehouse

TX 25/50 FM BROADCAST TRANSMITTER

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

Technical manual

Summary of Contents for TX 25/50

Page 1: ...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 la...

Page 2: ...jumpers 2 52 Multiplex Broadband Input 2 53 Stereo With Limiters 2 54 Stereo With Limiters Disabled 2 55 Mono From Two Channels 2 56 Mono From One Channel 2 6 Other Setup Considerations 3 Technical d...

Page 3: ...ring accuracy nor mally only found on expensive test equipment Local and remote personal computer control and metering are achievable via the innovative dual method RS232 interface The FM modulator se...

Page 4: ...el Failure to do so may increase the risk of equipment failure shock and fire hazard R F The N type R F power output socket contains R F voltages which may burn or present a shock Please make sure tha...

Page 5: ...D type pin out Pin 1 PLL failure alarm O C Pin 2 Reserved Pin 3 Reserved Pin 4 R F failure alarm O C Pin 5 R F failure alarm TTL Pin 6 Mod failure alarm TTL Pin 7 PLL failure alarm TTL Pin 8 R F Mute...

Page 6: ...up down buttons will allow power control if internally allowed The maximum output power is governed by the maximum power set adjustment see R F pwr control section If the frequency is set internally w...

Page 7: ...r as 8 represents 100 KHz on the 12 5 KHz switch 8 x 0 125MHz 0 1MHz 100KHz The LCD display on the front panel will display the frequency that you have set on the internal switches If you try to adjus...

Page 8: ...ill allow the LCD screen to provide adjustment of the R F power down from that maximum power set point This can be desir able in transmitter hire situations where you wish to govern the maximum output...

Page 9: ...e RS232 MODULATION FAILURE The Modulation failure alarm will be set if during normal operation the peak deviation of the transmitter drops and remains below 16 KHz The 16 KHz alarm level allows the al...

Page 10: ...your other signals via the push snap terminals a 9 way serial lead from your computer can be plugged into the expansion boards 9 way D type socket The above item is an optional extra and is available...

Page 11: ...software but it should be pretty much straight forward Operation The transmitter will respond to certain key presses and each one has a certain function See the list below for details of what key to p...

Page 12: ...gain as an example You press the R F mute key o and then press refresh screen key ENTER to get a status update The transmitters power control circuitry may not have had time to turn the r f power down...

Page 13: ...ereo 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 Thi...

Page 14: ...e There are two different standards in use worldwide In Europe and Africa the standard is normally 50uS This represents a lift of about 3dB at 3 KHz and 10dB at 10 KHz In the Americas and in Japan mor...

Page 15: ...tion This one jumper controls both channels because the gain reduction control voltage which this jumper disables is common to left and right Even with the limiter disabled you may still wish to use t...

Page 16: ...iter module and to the back panel multiplex output BNC socket See loopthrough mode below JUMPERS J1 ON J2 3 50 or 75 J4 5 LOUD or CLARITY J6 7 ON J8 ON J9 10 ON J11 ST J12 OFF Stereo with internal lim...

Page 17: ...ct the signal from the internal limiter and stereo encoder to an external piece of equipment before being reinjected back into the transmitter via the multiplex input socket The most common applicatio...

Page 18: ...tly boost loudness The gain controls on the back panel control the input drive to the limiter module and can be set so that limiting occurs for a given input level Factory setting is at maximum to ena...

Page 19: ...hould now have the multiplex and pilot setup at the correct level All that is left to do is to set the input gain controls to your desired settings For most applications where you require a compressed...

Page 20: ...any form of level control apart from the peak level clippers so we can set the system internal levels correctly 5 We should check that any offsets internal to the limiter are nulled out to keep distor...

Page 21: ...r 75KHz peak deviation at 400Hz The pre emphasis filter can put the 15KHz audio 17db higher than 400Hz We strongly advise you to ensure pre emphasis is built into any external equipment if you decide...

Page 22: ...level feed you may have to turn the gain controls down to stop internal clipping occurring prior to the limiter Please see note on pre emphasis at the end of the section You may also wish the limiter...

Page 23: ...t level required to achieve limiting is frequency dependent due to the characterisTics of the pre emphasis curve There is 17dB more gain into the limiter with a 15KHz input signal compared to a freque...

Page 24: ...d use as simple as possible FREQUENCY FINE TUNE WARNING ADVANCED TECHNICIANS ONLY While the frequency is controlled by the phase locked loop system the stability is governed by the stability of the re...

Page 25: ...approvals 3 25W TX25 5 50W TX50 N type 50 ohm better than 65 dbc 75 dbc 87 5 108 MHz 100KHz from LCD or 12 5 KHz from internal switches Internal switches or LCD system Dual speed Phase locked loop 500...

Page 26: ...Right audio signals are applied to balanced input XLR sockets on the back panel The balanced audio signals are fed to IC1 IC4 which are configured as differential amplifiers to convert the balanced i...

Page 27: ...r is buffered by output op amp IC15 which also provides a fixed output level of 6dbu which is fed to the multiplex output BNC socket on the back panel as well as to one side of the loopthrough jumper...

Page 28: ...ge adjusted over approx 1 to 28 volt range The RF output side of L4 and its network of series and shunt capactiors consisting of C18 21 provide impedance matching to the input of the elliptical low pa...

Page 29: ...nto the LCD display by the LCD control bits on PORTC PORTE 3 bits has the remaining A D inputs Bit 0 is the PA volts Bit 1 is the Rev RF power and bit 2 is for the PA temperature The Microcontrollers...

Page 30: ...TX25 50 FM Transmitter technical manual page 30 Technical data 3 3 BLOCK DIAGRAM...

Page 31: ...ils W1 yellow green 16 0 2 W2 blue 24 0 2 W3 brown 24 0 2 W4 red 24 0 2 tri rated W5 yellow 24 0 2 W6 black 24 0 2 tri rated W7 black 24 0 2 W8 red 24 0 2 FILTERED IEC MAINS SOCKET RF MOD MON BNC S RG...

Page 32: ...TX25 50 FM Transmitter technical manual page 32 Technical data 3 51 LCD control board...

Page 33: ...TX25 50 FM Transmitter technical manual page 33 Technical data 3 52 Power amplifier board...

Page 34: ...TX25 50 FM Transmitter technical manual page 34 Technical data 3 531Combo board limiter section...

Page 35: ...TX25 50 FM Transmitter technical manual page 35 Technical data 3 532 Combo board stereo encoder section...

Page 36: ...TX25 50 FM Transmitter technical manual page 36 Technical data 3 533 Combo board PLL exciter section...

Page 37: ...or IC1 PIC16F877 40 pin 8 Bit micro Controller IC2 CA3240 op amp T1 TIP32A PNP Transistor SW1 3 BUTTONS Blue buttons CON1 10W IDC IDC boxed header CON2 16W IDC IDC boxed header LCD1 122x32 NAN YA LMD6...

Page 38: ...0uF 16V Monolithic Ceramic 2 5 pitch C13 2 2 uF 16V Miniature Radial Electrolytic C14 100n Y5V Monolithic Ceramic 2 5 pitch C15 82pF Ceramic Plate 2 5 pitch 680 C16 100n Y5V Monolithic Ceramic 2 5 pit...

Page 39: ...n IC Holders X 14 14 PIN 14 PIN 14 Pin IC Holders X 1 16 PIN 16 PIN 16 Pin IC Holders X 3 18 PIN 18 PIN 18 Pin IC Holders X 2 INDUCTORS L1 3 9mH 10RB Radial Inductor L2 4 7mH 10RB Radial Inductor L3 M...

Page 40: ...l Oxide R103 5K1 1 4 Watt Metal Oxide R104 5K3 1 4 Watt Metal Oxide R105 100R 1 4 Watt Metal Oxide R106 3K6 1 4 Watt Metal Oxide R107 11K 1 4 Watt Metal Oxide R108 75R 1 4 Watt Metal Oxide R109 10K 1...

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