BW Broadcast TX25 User manual

TX25/50 FM Broadcast Transmitter
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
Technical manual

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.
If you intend to connect a MPX signal to the MPX input BNC connector you will
need to move J1 (MPX loop-through) to the OFF position.
Examples of congurations requiring setting J1 to OFF include:
Routing the internal MPX signal through an external RDS encoder.
Connecting an external audio processor or stereo generator to the
transmitter.
Connecting a re-broadcast or STL receiver to the transmitter.
Consult the manual for further information on the transmitter’s jumpers and con-
nections.
●
●
●

BW Broadcast technical manual Page 3
CONTENTS
1. Introduction
1.1 TX FM Transmitter
1.2 Safety
1.3 Quick setups
1.4 Front And Rear Panels
1.5 Control And Monitor LCD
2. Installation And Setup
2.1 Frequency Setup
2.2 R.F. Power Setup
2.3 Alarms
2.4 RS232 Control & Monitoring
2.41 Windows remote control application
2.42 Terminal control of the transmitter
2.5 Modes Of Operation
2.51 A guide to the 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 data
3.1 Specifications
3.2 Circuit Description
3.21 Combo board
3.22 LCD control board
3.23 Power amplifier board
3.3 Block Diagram
3.4 Internal Wiring / Case Overview
3.5 Schematics
3.51 Combo section
3.511 Limiter section
3.512 Coder section
3.513 Exciter section
3.52 LCD control section
3.53 Power amplifier section
3.6 Parts List
3.61 Combo board parts list
3.62 LCD control board parts list
3.63 Power amplifier board parts list

BW Broadcast technical manual Page 4
Introduction
1.1 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. output of the MOS-FET power amplifier stage.
RF, audio and other parameters are shown on the LCD graphics display. This display offers a very easy method
of transmitter parameter monitoring and a new level of ease for setup and installation, with metering accuracy
normally only found on expensive test equipment. Local and remote personal computer control and metering are
achievable via RS232 interface and there's an alarm I/O as well.
The FM modulator section employs a dual speed “virtual VFO” system for extremely low audio distortion and
excellent stereo performance.
A built in high specification stereo encoder provides crystal clear stereo sound and combined with the internal lim-
iter a fully compliant “plug and play” all in one low power broadcast transmitter.
For future compatibility all settings are switchable with on board jumpers. The stereo and/or limiter settings can be
switched in and out to suit the requirements of any external broadcast equipment you may have now and in the
future.
The lightweight universal mains input design ensures a high reliability efficient design compatabile with any mains
system in the world.

BW Broadcast technical manual Page 5
Introduction
1.2 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. The switched mode supplies are universal input fully approved type. They are
non serviceable modules and should be fully replaced should they fail.
FUSES
Only use fuses with the specified voltage and current ratings as stated on the back panel. 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 that the equipment is connected to an adequately rated load or antenna system while in opera-
tion.
TOXIC HAZARD
This equipment includes R.F. components that may contain Beryllium oxide which is a highly toxic sub-
stance that could be hazardous to health if inhaled or ingested. Care should be taken when replacing or
discarding such devices. Seek expert advice from the manufacturer should you physically damage a device
that contains Berillyium Oxide. The main R.F. output power transistor contains Beryllium oxide.
OTHER SAFETY CONSIDERATIONS
Do not operate this equipment in the presence of flammable gases, fumes or liquids
Do not expose this equipment to rain or water.
CE CONFORMANCE
This device complies with the requirements of the 1995/5/EC Radio and Telecommuni-
cations Terminal Equipment (R&TTE). The equipment will meet or exceed the following
standards: EN 60215:1996 (Safety Requirements for Radio Transmitting Equipment),
EN 301 489-11 (ERM/EMC for Radio Equipment, Part 11 Specific Conditions for FM
Transmitters), EN 302 018-2 ERM (Transmitting Equipment for FM Radio Broadcasting
service)
The operating frequencies of this transmitter may not be harmonised in the intended
countries of use. The user must obtain a license before using the product in the intend-
ed country of use. Ensure respective country licensing requirements are complied with.
Limitations of use can apply in respect of operating frequency, transmitter power and/or
channel spacing.
WEEE COMPLIANCE
BW Broadcast Ltd is registered with Northern Compliance PCS number WEE/P3438PR/
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.
This appliance has been designed and manufactured with high quality materials and components that can
be recycled and reused. Electronic appliances are liable to contain parts that are necessary in order for the
system to work properly but which can become a health and environmental hazard if they are not handled
and disposed of in the proper way. Consequently, please do not throw your inoperative appliance with the
household waste. Having purchased this appliance it is your responsibility to dispose of this equipment
appropriately.

BW Broadcast technical manual Page 6
Introduction
1.3 Quick set-up guide
Using a transmitter stand-alone (without RDS encoder)
This set-up uses the built-in audio limiter and stereo generator. The transmitter as shipped from factory is already
configured for this set-up, so there are no internal changes to be made.
Place a transmitter in a well ventilated space. If it's rack-mounted, leave at least 1U free above and be-
low it for adequate cooling.
Connect the antenna to the RF output N-connector on the back of the transmitter.
Connect the left and right program audio signals to the XLR input connectors on the back of the transmit-
ter.
Plug in the power cord to the transmitter.
Once the transmitter is operating, set the correct carrier frequency from the front panel (this can also be
locked and set internally).
Adjust the desired power output level using front panel. Check reflected power is OK.
Check the gain reduction of the built-in limiter - it should be doing a couple of dB with normal program
level. 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!
1.
2.
3.
4.
5.
6.
7.

BW Broadcast technical manual Page 7
Introduction
1.3 Quick set-up guide
Using a transmitter stand-alone with RDS encoder
This set-up uses the built-in audio limiter and stereo generator.
Remove the screws that hold the lid of the transmitter and remove the lid.
Locate the main board on the right side of the transmitter. Locate jumper J1 right behind the BNC con-
nectors. Move it to down position (Loop-through off).
Reassemble the lid back on.
Place a transmitter in a well ventilated space. If it's rack-mounted, leave at least 1U free above and be-
low it for adequate cooling.
Connect the antenna to the RF output N-connector on the back of the
transmitter.
Connect the left and right program audio signals to the XLR input con-
nectors on the back of the transmitter.
Connect the Baseband/MPX output on the back of the transmitter to
the MPX input of the RDS encoder.
Connect the MPX output of the RDS encoder to the MPX input on the
back of the transmitter.
Plug in the power cord to the transmitter.
Once the transmitter is operating, set the correct carrier frequency
from the front panel (this can also be locked and set internally).
Adjust the desired power output level using front panel. Check reflected
power is OK.
Check the gain reduction of the built-in limiter - it should be doing a couple of dB with normal program
level. If necessary adjust the audio input level trimmers on the back of the transmitter.
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!
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
Audio processor
INOUT
MPX
BW Broadcast
Transmitter
RF OUT IN OUT
MPX
Audio processor
INOUT
MPX
BW Broadcast
Transmitter
RF OUT IN OUT
MPX
RDS encoder
IN OUT
MP X
Audio processor
BW Broadcast
Transmitter
RF OUT IN OUT
MPX
RDS encoder
IN OUT
RDS
PIL OT
OUTIN
SCA PILOT
OUT
MPX
RDS encoder
INOUT
MPX
BW Broadcast
Transmitter
RF OUT IN OUT
MPX
MPX connections

BW Broadcast technical manual Page 8
Introduction
1.3 Quick set-up guide
Using a transmitter with external audio processor/stereo generator
but without RDS encoder
Remove the screws that hold the lid of the transmitter and remove the lid.
Locate the main board on the right side of the transmitter. Locate jumper J1 right behind the BNC con-
nectors. Move it to down position (Loop-through off).
Reassemble the lid back on.
Place a transmitter in a well ventilated space. If it's rack-mounted, leave at least 1U free above and be-
low it for adequate cooling.
Connect the antenna to the RF output N-connector on the back of the
transmitter.
Connect the MPX output of your audio processor (or stereo generator)
to the MPX input on the back of the transmitter.
Plug in the power cord to the transmitter.
Once the transmitter is operating, set the correct carrier frequency
from the front panel (this can also be locked and set internally).
Adjust the desired power output level using front panel. Check reflect-
ed power is OK.
Check the modulation level - if the modulation level is low, adjust the
MPX output level on your audio processor (or stereo generator) and/or the
MPX input level on the back of the transmitter. The maximum modulation should not exceed 75kHz.
Check the documentation that came with your audio processor on how to set/check the proper pilot
injection 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!
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Audio processor
INOUT
MPX
BW Broadcast
Transmitter
RF OUT IN OUT
MPX
Audio processor
INOUT
MPX
BW Broadcast
Transmitter
RF OUT IN OUT
MPX
RDS encoder
IN OUT
MP X
Audio processor
BW Broadcast
Transmitter
RF OUT IN OUT
MPX
RDS encoder
IN OUT
RDS
PIL OT
OUTIN
SCA PILOT
OUT
MPX
RDS encoder
INOUT
MPX
BW Broadcast
Transmitter
RF OUT IN OUT
MPX
MPX connections

BW Broadcast technical manual Page 9
Introduction
1.3 Quick set-up guide
Using a transmitter with external audio processor/stereo generator
and with RDS encoder (in-line connection)
Remove the screws that hold the lid of the transmitter and remove the lid.
Locate the main board on the right side of the transmitter. Locate jumper J1 right behind the BNC con-
nectors. Move it to down position (Loop-through off).
Reassemble the lid back on.
Place a transmitter in a well ventilated space. If it's rack-mounted,
leave at least 1U free above and below it for adequate cooling.
Connect the antenna to the RF output N-connector on the back of
the transmitter.
Connect the MPX output of your audio processor (or stereo gen-
erator) to the MPX input of your RDS encoder.
Connect the MPX output of your RDS encoder to the MPX input
on the back of the transmitter.
Plug in the power cord to the transmitter.
Once the transmitter is operating, set the correct carrier frequency from
the front panel (this can also be locked and set internally).
Adjust the desired power output level using front panel. Check reflected power is OK.
Check the modulation level - if the modulation level is low, adjust the MPX output level on your audio
processor (or stereo generator), RDS encoder and/or the MPX input level on the back of the transmitter.
The maximum modulation should not exceed 75kHz.
Check the documentation that came with your audio processor on how to set/check the proper pilot
injection level.
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!
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
Audio processor
INOUT
MPX
BW Broadcast
Transmitter
RF OUT IN OUT
MPX
Audio processor
INOUT
MPX
BW Broadcast
Transmitter
RF OUT IN OUT
MPX
RDS encoder
IN OUT
MP X
Audio processor
BW Broadcast
Transmitter
RF OUT IN OUT
MPX
RDS encoder
IN OUT
RDS
PIL OT
OUTIN
SCA PILOT
OUT
MPX
RDS encoder
INOUT
MPX
BW Broadcast
Transmitter
RF OUT IN OUT
MPX
MPX connections

BW Broadcast technical manual Page 10
Introduction
1.3 Quick set-up guide
Using a transmitter with external audio processor/stereo generator
and with RDS encoder (sidechain connection)
This is the best connection in terms of pilot and RDS subcarrier phase syncronization and MPX spectrum cleanli-
ness.
Remove the screws that hold the lid of the transmitter and remove the lid.
Locate the main board on the right side of the transmitter. Locate jumper J1 right behind the BNC con-
nectors. Move it to down position (Loop-through off).
Reassemble the lid back on.
Place a transmitter in a well ventilated space. If it's rack-
mounted, leave at least 1U free above and below it for
adequate cooling.
Connect the antenna to the RF output N-connector on the
back of the transmitter.
Connect the MPX output of your audio processor (or stereo
generator) to the MPX input on the back of the transmitter.
Connect the Pilot output of your audio processor (or stereo
generator) to the Reference input on your RDS encoder.
Connect the MPX output of your RDS encoder to the SCA
input on your audio processor.
Plug in the power cord to the transmitter.
Once the transmitter is operating, set the correct carrier frequency from the front panel (this can also be
locked and set internally).
Adjust the desired power output level using front panel. Check reflected power is OK.
Check the modulation level - if the modulation level is low, adjust the MPX output level on your audio
processor (or stereo generator) and/or the MPX input level on the back of the transmitter. The maximum
modulation should not exceed 75kHz.
Check the documentation that came with your audio processor on how to set/check the proper pilot
injection level.
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!
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
Audio processor
INOUT
MPX
BW Broadcast
Transmitter
RF OUT IN OUT
MPX
Audio processor
INOUT
MPX
BW Broadcast
Transmitter
RF OUT IN OUT
MPX
RDS encoder
IN OUT
MP X
Audio processor
BW Broadcast
Transmitter
RF OUT IN OUT
MPX
RDS encoder
IN OUT
RDS
PIL OT
OUTIN
SCA PILOT
OUT
MPX
RDS encoder
INOUT
MPX
BW Broadcast
Transmitter
RF OUT IN OUT
MPX
MPX connections