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.
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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

BW Broadcast technical manual Page 11
Introduction
1.4 FRONT AND REAR PANELS
1. Left audio input 2. Left Input gain 3. Right input gain 4. Right audio input 5. MPX output 6. MPX level control 7. MPX Input 8. I/O + Alarms 9. RS232 10. R.F. output 11. Power socket 12. Chassis ground post 13. RF monitor output -50dBc (not suitable for harmonic measurements)
I/O - Alarms D-type connector pinout: Pin 1 MOD failure alarm (TTL Pin 2 PLL failure alarm (TTL) Pin 3 RF failure alarm (TTL) Pin 4 RF Mute Pin 5 +18V DC 200mA Pin 6 MOD failure alarm (OC) Pin 7 PLL failure alarm (OC) Pin 8 RF failure alarm (OC) Pin 9 GND
XLR Audio input connectors
FAULT
VSWR TEMP
T X 5 0
17 18
121 2 3 4 5 6 7 8, 9 10 11
13, 14 15 16
14. Modulation monitor output (buffered multiplex, nominally 3V peak-to-peak for 75kHz) 15. VSWR and temperature fault LEDs 16. Maximum forward power adjust 17. LCD display 18. Up / Down frequency buttons
PIN1 GND PIN2 Hot (+) PIN3 Cold (-)
FAULT
VSWR TEMP
T X 3 0 0
1
2
3
FAULT
VSWR TEMP
T X 3 0 0
5 4 3 2 1
9 8 7 6

BW Broadcast technical manual Page 12
Introduction
1.5 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 frequency. You
can move through the screens by pressing the NEXT button, which will display them in the following order.
Main parameter screen.
This shows together the three most important transmitter
parameters. Frequency, R.F. output power and the peak
deviation.
Frequency display and control
This screen will display the frequency and PLL locked condi-
tion. The up and down buttons will allow 100 kHz frequency
steps from 87.5 to 108Mhz if the internal switches are set
to 4440. If the frequency is set internally with the rotary
switches then the up / down buttons will give a ‘not allowed’
message
Peak deviation
This display indicates the peak and average deviation. Peak
deviation is shown both numerically and as a moving single
pixel wide bar. Average deviation is shown with the solid
black bar. Over-deviation will display an exclamation ( ! )
Gain reduction
This display indicates the amount of gain reduction of the
internal audio limiter. The range is 0 to 24 decibels of gain
reduction.
Power supply
Power amplifier voltage is shown together with the transmit-
ters secondary supply that feeds the exciter section. 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.

BW Broadcast technical manual Page 13
Installation and setup
2.1 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. To meet this requirement you will need to set the frequency internally with the dial
switches.
The switches have a silkscreen diagram next to them on the board (see diagram below) clearly indicating what
each switch represents.
The top dial switch represents the value selected x 10 Mhz with the exception of ‘0’ which represents 10 so when
selected would equal 100 Mhz.
The second dial switch represents the value selected x 1 Mhz.
The third dial switch represent the value selected x .1 Mhz (100 kHz)
The bottom switch represents the value selected x .0125 Mhz (12.5 kHz)
For example:
FREQ SWITCHES (MHz)
X10 X1 X.1 X.0125
87.90 ‘8’ ‘7’ ‘9’ ‘0’
98.75 ‘9’ ‘8’ ‘7’ ‘4’
100.00 ‘0’ ‘0’ ‘0’ ‘0’
104.225 ‘0’ ‘4’ ‘2’ ‘2’
108.00 ‘0’ ‘8’ ‘0’ ‘0’
As you can see, the switches directly read the frequency with the
exception of frequencies above 100 Mhz, where the top switch being set at ‘0’
represents ‘10’. The X0.125 ‘offset’ switch is only used when you want to pro-
vide a shift to the carrier of between 12.5 kHz and 112.5 kHz. Note that setting
the switch on 8 or 9 will have the same effect as setting the previous switch
(100 kHz) 1 position higher, 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 adjust the frequency with the front panel up / down buttons you will get a ‘ NOT ALLOWED ‘ message appear-
ing on the LCD display. This protects against unauthorized front panel frequency changes when the frequency
has been set internally with the dial switches.
The TX will load the switch values at power up. You will need to remove the mains power to the transmitter
and then reapply it if you want to change the frequency by using the direct reading switches
LCD front panel frequency selection.
If you want to control the frequency from the front panel LCD con-
trol system you will need to set the internal switches to 4440. The
transmitter will pass frequency control to the LCD control system
and the frequency can be moved up and down by pressing the
NEXT button until the frequency menu is displayed. The other two
buttons control the UP and DOWN frequency selection. PLL lock
status is also displayed on this screen.
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.
Note that some pcb’s have “set to 4444 for
front panel LCD control”. This is an error that
will cause a +50kHz offset to the frequency set
on the LCD screen. Please set to 4440 unless
you specifically want the offset.
Frequency selection switches on main board
Fine frequency control. Do not adjust unless you
know what you are doing. Consult advanced setup
section of manual for more information.

BW Broadcast technical manual Page 14
Installation and setup
2.2 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. This is to comply with regulatory body’s that stipulate that the transmitter is not to have it’s parameters
adjustable from the front panel. In this case you must use the maximum power set control to set the transmitters
power. This control will give the full power range adjustment.
If the transmitter has been internally set to 4440 with the dial switches then you can also control the power from
the LCD screen’s R.F. power menu’s up and down buttons. A “not allowed” message will be displayed to the user
if the dial switches are not set to 4440
RS232 power control will over-ride the power control restrictions caused by having the frequency set
internally (not set to 4440).
DIGITAL POWER CONTROL
When the power is to be controlled from the front panel the max power set POT takes on a new role of setting the
maximum power of the transmitter. If you want the LCD screen to have full power range control of the transmitter
you will need to ensure that the max power set control is at maximum power. Otherwise your control range may
be limited. This feature enables you to limit the transmitters maximum power to a fixed level but to still 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 to a fixed level but to allow the customer (hirer of the transmitter)
to run the power of the transmitter at a lower level if they so decide.
The maximum power set is positioned to the lower left of the LCD screen
on some models, other models may not have the hole in the front panel
and you will need to remove the lid of the transmitter to access the adjust-
ment which will be in the same position but on the other side of the PCB. You will need a small ‘tweaker style’ flat-
head screwdriver to adjust the pot. This control is quite delicate so try to not be too heavy handed in it’s adjust-
ment.
Please note that the VSWR and temperature protection circuitry will turn back the R.F. power if a fault con-
dition exists. Make sure that you have a good VSWR (low reverse power reading) before setting the R.F.
power as the removal of a fault condition may cause the R.F. power to increase.
RF POWER MUTE (analogue)
There is a pin (2) on the back panel I/O D-type that can be pulled low to mute the trans-
mitters RF power.
RF POWER MUTE (digital/RS232)
The transmitters RF power output can be muted via the RS232 control system.
Terminal software can mute/unmute the RF power with the ‘o’ and ‘f’ commands
respectively.
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.
FUSE
123456 7 8 911 13
12
10
TX150/300 FM TRANSMITTER
FUSE
123456 7 8 9 11 131210
TX25/50 FM TRANSMITTER
FUSE
123456 7 8 9 11 131210
TX1 FM TRANSMITTER
B W - T X 6 0 0
FAULT
VSWR TEMP
1 2 3 4 5
6 7 8 9

BW Broadcast technical manual Page 15
Installation and setup
2.3 ALARMS
The transmitter has three alarms that can alert the broadcaster if one of the following fails:
R.F. POWER, PLL LOCK, MODULATION
The alarms when set are available on the back panel 9-pin D-type. Each alarm has an open collector (OC) and
a TTL level contact on the D-type. The alarm induced active open collectors can pull down any external signals
and the TTL outputs will provide a 5 Volt indication. The alarm is also visible if any RS232 monitoring (through
Windows Remote Control application or terminal software) is employed.
For the alarms to function correctly the transmitter must be left on the default menu screen. This is the screen that
displays frequency, R.F. power and peak deviation. To ensure that the alarm system functions correctly the trans-
mitter will return to the default menu screen if the LCD is left on another menu screen for more than 5 minutes.
R.F. POWER.
The R.F. power alarm will be set if the R.F. power falls below a threshold level during normal operation.
This threshold is set below the normal operating lowest wattage available from the transmitter. If you
require a different setting for the alarm, contact our tech dept. The alarm will only be set if the fault condi-
tion exists for sixty seconds or more. You will need to reset the transmitter to clear the alarm/s or you can
do it via RS232 connection.
PLL LOCK.
The PLL lock alarm will be set if the transmitters falls out of frequency lock during normal operation. The
alarm will only be set if the fault condition exists for sixty seconds or more. You will need to reset the trans-
mitter to clear the alarm/s or you can do it via RS232 connection.
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 alarm to be set if the audio feed to
the transmitter fails even if the stereo pilot internal to the transmitter is still modulating the transmitter. The
alarm will only be set if the fault condition exists for sixty seconds or more. You will need to reset the trans-
mitter to clear the alarm/s or you can do it via RS232 connection.
MORE INFO ON ALARMS
The three alarms are available on the back panel D-type connector. The pin-outs are shown on the rear
panel diagram. The three alarms are available as TTL level and as open collector outputs. The TTL level
outputs are active high in the event of an alarm. The open collector outputs are ON in the event of an alarm
and will pull down any external levels. The open collectors can sink 100 mA MAX with an absolute maxi-
mum switched voltage of 25 volts.
The D-type connector can also supply 18 volts at 200 mA that can be used for pull-ups on the open collec-
tor alarm outputs and for your own external switching circuitry.
The RS232 interface provides the ability to reset the alarms either through Windows Remote Control appli-
cation or terminal software. 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.

BW Broadcast technical manual Page 16
Installation and setup
2.4 RS232 CONTROL AND MONITORING
The TX range of transmitters can be monitored or controlled from a personal computer either locally or remotely.
The Transmitters can “chat” either by a windows application or via a standard serial terminal program. The win-
dows application is the more versatile option and is to be preferred but the ability to use a terminal program can
prove useful in the absence of the windows application or a computer that runs windows.
2.41 Windows remote control application
The latest version of Windows remote control application can be downloaded from:
http://www.bwbroadcast.com
Installation
After downloading just click on the .msi file to run the set up program. The set up will place icons in both the
Windows start menu and on your desktop. Simply run the program by clicking on icon from either location.
Running the application
When started the application will resemble the picture to the right.
The application can connect to any COM port currently available on your com-
puter that is running the application. Connect a serial cable between the RS232
connector on the rear of the transmitter and one of your computers COM ports. If
you are using a codec or other STL device then you may be able to connect that
device in line to act as part of the serial link.
Selected the COM port you want to use and then click the Connect button.
If the application is able to connect to the transmitter then you will be presented with a screen similar to the one
above. Once connected you should be able to monitor all the parameters of the transmitter as well as being able
to mute the R.F., change the frequency, change the R.F. power and reset any alarm flags that have been set.
2.42 Terminal control of the transmitter
Installation
Please see the instructions for your terminal software package to find out how to connect to a remote serial
device. 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
Remote Control Applictiona startup screen
Remote Control Application

BW Broadcast technical manual Page 17
Installation and setup
from the Start menu. Select direct to COM port x where x is the com port
that the transmitter is connected to. You will be presented with a dialog box
like the one shown to the right. Select 9600, 8, none ,1 with hardware flow
control and then click OK.
If you are using another terminal program then you may need to consult the
documentation for that software, but it should be pretty much straight for-
ward.
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 press for each
function.
The most important key press is the ‘Enter’ key. This will need to be pushed
as soon as you connect to the transmitter so you can get the transmitter to
refresh your terminal window with the transmitters sta-
tus and parameters.
The transmitter won’t respond to any of the other key
presses until it detects the ‘Enter’ key is pressed. Once
the Enter key is pressed the transmitter will listen out
for other key presses for 60 seconds. This Initial ‘Enter’
key validation and time window is a safety feature to
prevent the transmitter from detecting an erroneous
key press such as R.F. mute and causing a service
affecting problem.
After performing a function you may need to press
the ‘Enter’ key to see a response to your function. For
example, If you pressed ‘o’ for R.F. Mute you would
not see the effect of the R.F. power change until you
refreshed the screen again because the terminal win-
dow would still be showing the transmitters R.F. power
from the previous ‘Enter’ (screen refresh) command,
prior to you performing the R.F. mute command.
The frequency change key’s will perform an auto-
matic 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 command. In some circumstances you may need to press
the refresh screen key several times in order to see what’s hap-
pening. Take the R.F. mute function again 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 con-
trol circuitry may not have had time to turn the R.F. power down
into full R.F. mute by the time it has sent back to you the status
requested by the refresh screen command. It does no harm to
wait a second or two before asking for a refresh screen or by ask-
ing for several refresh screens by pressing the 'Enter’ key a few
times in succession.
Hyper Terminal connection
Hyper Terminal window
KEY COMMAND
1 Frequency up
2 Frequency down
3R.F. power up
4 R.F. power down
5 reserved
6 Reset alarms (all to 0 / off)
o Mute R.F.
f Unmute R.F.
ENTER Refresh screen
FREQUENCY
FWD R.F. PWR
REV R.F. PWR
PEAK MOD
LIMITER G.R.
P.A. VOLTS
AUX VOLTS
P.A. TEMP
ALARMS
R.F. FAIL PLL FAIL MOD FAIL
1=alarm, 0=no alarm

BW Broadcast technical manual Page 18
Installation and setup
J1 MPX loopthrough
J12 Mono from left
J2 Right pre-emphasis
J4 Right Loud/Clarity
VR3-4 Limiter offset trim
J3 Left Pre-emphasis
J5 Left Loud/Clarity
J7 Left Lim. Clipper
J6 Right Lim. Clipper
J8 Limiter On/Off
J9 Left filter Clipper
J10 Right filter Clipper
VR6 Pilot level control
J11 Pilot On/Off (stereo)
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. The advanced setup procedure pages that follow provide a little more information on each mode as well as
providing some information on setting the equipment up accurately if you have access to some test equipment.
2.51 A guide to the jumpers
Main combo board

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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.
Jumper 1: MPX loopthrough
The default position is ON.
This is where you want the audio left and right XLR sockets on the back of the board to be the signal source,
duly limited and stereo coded internally. Only when you want to use the rear BNC socket for a complete
multiplex (MPX) input for the broadcast should you change the position of this link.
If the link is in the OFF position, only signals from an external encoder or processor will be accepted, unless
the internal coder has been ‘loop-throughed’ (see later).
Jumpers 2 and 3: Pre-emphasis 0 / 50 / 75 µs
The default position is 50 µs (75 µs/Japan).
What is pre-emphasis?
Pre-emphasis is the treble boost that must be applied to all FM broadcasts to compensate for the treble cut
(de-emphasis) present in every receiver. The aim of this process is to reduce noise in the broadcast path
without degrading the audio.
The precise nature of the treble boost is defined by a time-constant in microseconds, which describes the
resistor/capacitor network that will produce the appropriate 6dB per octave treble boost curve.
There are two different standards in use worldwide.
In Europe and Africa, the standard is normally 50 µs. This represents a lift of about 3dB at 3 kHz, and
10dB at 10 kHz. In the Americas, and in Japan, more boost is in use with a network of 75 µs, about 3dB
up at 2 kHz.
Jumpers 2 & 3 may either link the 50 µs pins, the 75 µs pins, or not link any pins, but be fixed to just one of
them for safekeeping, producing no pre-emphasis - ‘0’.
The effects of pre-emphasis
The absence of any pre-emphasis will result in a broadcast sounding noticeably lacking in treble. Applying
50 µs pre-emphasis will correct the situation in European receivers (75 µs in Μs/Japan). If you apply 75 µs
pre-emphasis when 50 is called for, the received sound will have some 3dB shelved treble boost above 3kHz.
This is undesirable. Conversely, if you only apply 50 where 75 is required, there will be 3dB treble loss, which
is also undesirable. You should not have to change the pre-emphasis setting from 50 to 75 or back unless
you are relocating the installation abroad where the standard is different.
However, whenever pre-emphasis is deliberately applied to your audio at some point before it enters the XLR
sockets on the back of the board, by an external processor for example, then you must set the pre-emphasis
to ‘0’, because pre-emphasis must only be applied once. Double pre-emphasis must be avoided because it
will make a signal sound far too bright and toppy.
Both Jumper 2 and Jumper 3 should be in the same position at all times because both left and right audio
channels should have the same treatment. 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).

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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 position)
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. This will help you establish which sound you prefer.
As before, both jumpers 4 and 5 should always be in the same position. These jumpers, like all the following
ones, do not affect the operation of the board when external MPX is used with Jumper 1 off.
Jumpers 6 and 7: Limiter clippers on/off
The default position for these jumpers is ON.
If they are to be switched off when external audio processing is used, careful monitoring of deviation is recom-
mended. The 15 kHz post-filter clippers must be switched off at the same time (J9/10).
These jumpers control the clippers applied to the signal after the limiter but before the 15kHz low-pass fil-
ters on the way into the stereo coder. Again, these jumpers work as a pair and do not affect external MPX
inputs.
Jumper 8: Limiter on/off
The default position for this jumper is ON, i.e. limiter active.
If you are using a pre-processed and limited signal and do not want the additional protection of the internal
limiters, their action can be disabled by putting Jumper 8 in the OFF position. 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 the pre-filter clippers (J6/7) and post-filter clippers
(see below, J9/10) for protection. Always observe the deviation produced very carefully for excesses above
75 kHz if you ever remove the action of the limiter or clippers.
Jumpers 9 and 10: 15kHz filter clippers on/off
The default position for these clippers, placed after the 15kHz filters on the input to the coder, is ON.
These clippers protect against over-deviation caused by signals which ‘ring’ in the 15kHz filter, even after
having been caught by the clipper before the filter. With certain pre-processed and filtered inputs, however,
they may be switched out of circuit. But keep a close eye on the deviation.
Don’t have these clippers switched on unless you also have the limiter clippers active. Otherwise, your signal
could go out of specification.
These jumpers work as a pair and don’t affect external MPX drives.
Jumper 11: Mono / Stereo
The default position is STEREO, pilot tone on.
This option allows you to remove or restore the stereo pilot tone, at a frequency of 19 kHz, normally sitting at
a level between 8 and 10% of total deviation.
It is this tone which alerts stereo FM receivers to the need to switch on their stereo decoders. The presence
of a pilot tone is all that is required for the ‘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 38 kHz subcarrier,
even when it is still present.