Crown FM30, FM100, FM250 User Manual

®

User's Manual

©2005 Crown Broadcast, a division of International Radio and Electronics, Inc.

25166 Leer Drive, Elkhart, Indiana, 46514-5425 U.S.A.

FM30/FM100/FM250

Broadcast Transmitter

[phone]

i

Revision Control

Revision Print Date

Initial Release (Rev. 0; K80620–6) February 1995
Revision 1 (K80664–4)November 1995
Revision 2 (K80664A2) March 1996
Revision 3 (100885–1) October 1996
Revision 4 (100885–2) July 1997
Revision 5 (900194-1) October 1997
Revision 6 (130758-1) April 2000

Revision 7 April 2002

Revision 8 April 2005

Important Notices

©2005, Crown Broadcast, a division of International Radio and Electronics, Inc.
Portions of this document were originally copyrighted by Michael P. Axman in 1991.
All rights reserved. No part of this publication may be reproduced, transmitted,

transcribed, stored in a retrieval system, or translated into any language in any
form by any means without the written permission of Crown International, Inc.

Printed in U.S.A.

Crown attempts to provide information that is accurate, complete, and useful.
Should you find inadequacies in the text, please send your comments to the follow­ing address:

International Radio and Electronics

25166 Leer Drive, P.O . Box 2000

Elkhart, Indiana, 46515-2000 U .S.A.

ii

ContentsContents

Contents

ContentsContents

Section 1—Getting Acquainted ..................................... 1–1

1.1 Your Transmitter ...............................................................................................1–2

1.2 Applications and Options...................................................................................1–3

1.2.1 Stand-Alone ..................................................................................................1–4

1.2.2 Backup..........................................................................................................1–4

1.2.3 Booster .........................................................................................................1–4

1.2.4 Exciter...........................................................................................................1–4

1.2.5 T ranslator......................................................................................................1–5

1.2.6 Satellator ......................................................................................................1–6

1.2.7 Nearcasting...................................................................................................1–6

1.3 T ransmitter/Exciter Specifications .....................................................................1–7

1.4 Receiver Specifications .....................................................................................1–9

1.5 Safety Considerations......................................................................................1–10

1.5.1 Dangers ......................................................................................................1–10

1.5.2 Warn ings ....................................................................................................1–10

1.5.3 Cautions......................................................................................................1–10

Section 2—Installation ............................................... 2–1

2.1 Operating Environment......................................................................................2–2

2.2 Power Connections ...........................................................................................2–2

2.2.1 AC Line Voltage Setting ................................................................................2–2

2.2.2 Fuses ............................................................................................................2–4

2.2.3 Battery Power ...............................................................................................2–5

2.3 Frequency (Channel) Selection ..........................................................................2–5

2.3.1 Modulation Compensator..............................................................................2–7

2.4 Receiver Frequency Selection............................................................................2–7

2.5 RF Connections...............................................................................................2–10

2.6 Audio Input Connections .................................................................................2–11

2.7 SCA Input Connections ...................................................................................2–12

2.8 Composite Input Connection ........................................................................... 2–12

2.9 Audio Monitor Connections.............................................................................2–13

2.10 Pre-emphasis Selection...................................................................................2–13

2.11 Program Input Fault Time-out...........................................................................2–14

2.12Remote I/O Connector.....................................................................................2–14

iii

Section 3—Operation................................................. 3–1

3.1 Initial Power-up Procedures ..............................................................................3–2

3.2 Power Switches.................................................................................................3–4

3.2.1 DC Breaker....................................................................................................3–4

3.2.2 Power Switch................................................................................................3–4

3.2.3 Carrier Switch...............................................................................................3–4

3.3 Front Panel Bar-Dot Displays.............................................................................3–5

3.3.1 Audio Processor Input ..................................................................................3–5

3.3.2 Highband and Wideband Display ..................................................................3–5

3.3.3 Modulation Display .......................................................................................3–5

3.4 Input Gain Switches ..........................................................................................3–6

3.5 Processing Control............................................................................................3–6

3.6 Stereo-Mono Switch..........................................................................................3–6

3.7 RF Output Control .............................................................................................3–7

3.8 Digital Multimeter..............................................................................................3–7

3.9 Fault Indicators .................................................................................................3–8

Section 4—Principles of Operation................................. 4–1

4.1 Part Numbering.................................................................................................4–2

4.2 Audio Processor Circuit Board ..........................................................................4–3

4.3 Stereo Generator Circuit Board..........................................................................4–4

4.4 RF Exciter Circuit Board ....................................................................................4–6

4.5 Metering Circuit Board ......................................................................................4–8

4.6 Motherboard .....................................................................................................4–9

4.7 Display Circuit Board.......................................................................................4–10

4.8 Voltage Regulator Circuit Board ......................................................................4–11

4.9 Power Regulator Circuit Board ........................................................................4–12

4.10 RF Driver/Amplifier (FM30) .............................................................................4–12

4.11 RF Driver (FM100/FM250)...............................................................................4–13

4.12 RF Amplifier (FM100/FM250) ..........................................................................4–13

4.13 Chassis ...........................................................................................................4–14

4.14 RF Output Filter & Reflectometer.....................................................................4–14

4.15 Receiver Circuit Board Option .........................................................................4–15

iv

Section 5—Adjustments and Tests ................................. 5–1

5.1 Audio Processor Adjustments ...........................................................................5–2

5.1.1 Pre-Emphasis Selection ................................................................................5–2

5.1.2 Pre-Emphasis Fine Adjustment .....................................................................5–2

5.2 Stereo Generator Adjustments ..........................................................................5–2

5.2.1 Separation ....................................................................................................5–2

5.2.2 Composite Output.........................................................................................5–2

Using a Modulation Monitor 5–3

5.2.3 19–kHz Level ................................................................................................5–4

5.2.4 19–kHz Phase...............................................................................................5–4

5.3 Frequency Synthesizer Adjustments ..................................................................5–4

5.3.1 Frequency (Channel) Selection......................................................................5–4

5.3.2 Modulation Compensator..............................................................................5–4

5.3.3 Frequency Measurement and Adjustment .....................................................5–4

5.3.4 FSK Balance Control .....................................................................................5–5

5.4 Metering Board Adjustments.............................................................................5–5

5.4.1 Power Calibrate.............................................................................................5–5

5.4.2 Power Set .....................................................................................................5–5

5.4.3 SWR Calibrate...............................................................................................5–5

5.4.4 P A Current Limit ...........................................................................................5–6

5.5 Motherboard Adjustments.................................................................................5–6

5.6 Display Modulation Calibration..........................................................................5–6

5.7 Voltage Regulator Adjustments .........................................................................5–6

5.8 Bias Set (RF Power Amplifier)...........................................................................5–7

5.9 Performance Verification ...................................................................................5–7

5.9.1 Audio Proof-of-Performance Measurements .................................................5–7

5.9.2 De-emphasis Input Network..........................................................................5–7

5.10 Carrier Frequency..............................................................................................5–8

5.11 Output Power ....................................................................................................5–8

5.12 RF Bandwidth and RF Harmonics......................................................................5–8

5.13 Pilot Frequency .................................................................................................5–8

5.14 Audio Frequency Response ...............................................................................5–9

5.15 Audio Distortion ................................................................................................5–9

5.16 Modulation Percentage......................................................................................5–9

5.17 FM and AM Noise..............................................................................................5–9

5.18 Stereo Separation..............................................................................................5–9

5.19 Crosstalk ...........................................................................................................5–9

5.19.1 Main Channel Into Sub ..............................................................................5–10

5.19.2 Sub Channel Into Main ..............................................................................5–10

5.20 38–kHz Subcarrier Suppression ......................................................................5–10

5.21 Additional Checks............................................................................................5–10

v

Section 6—Reference Drawings .................................... 6–1

6.1 Views ................................................................................................................6–2

6.2 Board Layouts and Schematics .........................................................................6–4

Section 7—Service and Support.................................... 7 –1

7.1 Service ..............................................................................................................7–2

7.2 24–Hour Support ..............................................................................................7–2

7.3 Spare Parts .......................................................................................................7–2

T ransmitter Output Efficiency .............................. Appendix–1

Glossary.................................................................G–1

Index................................................................Index–1

vi

I

INFORMATION

Section 1—Getting Acquainted

This section provides a general description of the FM30, FM100,
and FM250 transmitters and introduces you to safety conventions
used within this document. Review this material before installing

or operating the transmitter.

Getting Acquainted

1–1

I

1.1 Your Transmitter

The FM30, FM100, and FM250 are members of a family of FM stereo broadcast
transmitters. Crown transmitters are known for their integration, ease-of-use, and
reliability.

The integration is most apparent in the standard transmitter configuration which
incorporates audio processing, stereo generation, and RF amplification without
compromised signal quality. A single Crown transmitter can replace several pieces
of equipment in a traditional system.

Ease-of-use is apparent in the user-friendly front panel interface and in the instal­lation procedure. Simply select your operating frequency (using 4 internal
switches), add an audio source, attach an antenna, and connect AC or DC power
and you're ready to broadcast. Of course, the FM series of transmitters also feature
more sophisticated inputs and monitoring connections if needed.

Reliability is a Crown tradition. The first Crown transmitters were designed for
rigors of worldwide and potentially portable use. The modular design, quality
components, engineering approach, and high production standards ensure stable
performance.

Remote control and metering of the transmitter is made possible through a built­in I/O port. For more direct monitoring, the front panel includes a digital multi­meter display and status indicators. Automatic control circuitry provides protec­tion for high VSWR as well as high current, voltage, and temperature conditions.

Illustration 1–1 FM250 Stereo Broadcast Transmitter

This manual describes the FM30, FM100, and FM250 because all three transmit­ters share common design factors. Specific product differences are noted through­out the manual. In physical appearance, the FM30 differs from the FM100 and
FM250 in that it lacks the power amplifier and cooling fan assembly on the back
panel.

1–2

FM30/FM100/FM250 User's Manual

1.2 Applications and Options

Crown transmitters are designed for versatility in applications. They have been used
as stand-alone and backup transmitters and in booster, translator, satellator, and
nearcast applications. The following discussion describes these applications further.

Model numbers describe the configuration of the product (which has to do with its
intended purpose) and the RF output power which you can expect.

The number portion of each name represents the maximum RF output power. The
FM250, for example, can generate up to 250 watts of RF output power.

Suffix letters describe the configuration. The FM250T, for example, is the standard
or transmitter configuration. Except where specified, this document describes the
transmitter configuration. In this configuration, the product includes the following
components (functions):

❑ audio processor
❑ stereo generator
❑ RF exciter
❑ metering
❑ low-pass filter

Stereo
Generator

Audio
Processor

RF Exciter

®

FM250

Illustration 1–2 Standard (Transmitter) Configuration

Low-pass
Filtering

Metering

Getting Acquainted

1–3

I

1.2.1 Stand-Alone

In the standard configuration, the FM30, FM100, and FM250 are ideal stand-alone
transmitters. When you add an audio source (monaural, L/R stereo, or composite
signal), an antenna, and AC or DC power, the transmitter becomes a complete FM
stereo broadcast station, capable of serving a community.

As stand-alone transmitters, Crown units often replace multiple pieces of equip­ment in a traditional setup (exciter, audio processor, RF amplifier).

1.2.2 Backup

In the standard configuration, Crown transmitters are also used in backup applica­tions. Should your primary transmitter become disabled, you can continue to
broadcast while repairs take place. In addition, the FM transmitters can replace
disabled portions of your existing system including the exciter, audio processor, or
amplifier. Transfer switches on each side of the existing and backup transmitters
make the change-over possible with minimal downtime.

The DC operation option of the FM30, FM100, and FM250 make them attractive
backup units for those times when AC power is lost.

1.2.3 Booster

Also in the standard configuration, Crown transmitters have been used as booster
transmitters. Booster applications typically involve certain geographic factors
which prevent your system from broadcasting to the full coverage area allowable.
For example, a mountain range might block your signal to a portion of your
coverage area. Careful placement of a Crown transmitter, operating on the same
frequency as your primary transmitter, can help you reach full coverage.

1.2.4 Exciter

In addition to the standard configuration, the FM30, FM100, and FM250 are
available in optional configurations to meet a variety of needs.

An "E" suffix, as in the FM30E, for example, represents an exciter-only configura­tion. In this configuration, the audio processor and stereo generator boards are
replaced with circuitry to bypass their function. The exciter configurations are the
least expensive way to get Crown-quality components into your transmission
system.

You might consider the Crown exciter when other portions of your system are
performing satisfactorily and you want to maximize your investment in present
equipment.

1–4

FM30/FM100/FM250 User's Manual

1.2.5 Translator

A receiver configuration (FM100R, for example) replaces the audio processor and
stereo generator boards with a receiver module. This added feature makes the
FM30, FM100, and FM250 ideal for translator service in terrestrial-fed networks.
These networks represent a popular and effective way to increase your broadcasting
coverage. Translators, acting as repeater emitters, are necessary links in this chain
of events.

Traditionally, network engineers have relied on multiple steps and multiple pieces
of equipment to accomplish the task. Others have integrated the translator
function (receiver and exciter) to feed an amplifier. Crown, on the other hand,
starts with an integrated transmitter and adds a solid-state Receiver Module to
form the ideal translator.

Receiver
Module
(option)

Frequency
Selection

®

RF In

RF Exciter

Metering

Low-pass
Filter

RF Out

FM250

Illustration 1–3 Crown's Integrated Translator

This option enables RF in and RF out on any of Crown’s FM series of transmitters.
In addition, the module supplies a composite output to the RF exciter portion of
the transmitter. From here, the signal is brought to full power by the built-in
power amplifier for retransmission. The Receiver Module has been specifically
designed to handle SCA channel output up to 100 kHz for audio and high-speed
data.

FSK ID programming is built-in to ensure compliance with FCC regulations
regarding the on-air identification of translators. Simply specify the call sign of
the repeater station when ordering. Should you need to change the location of the
translator, replacement FSK chips are available. The Receiver Module option
should be ordered at the time of initial transmitter purchase. However, an option
kit is available for field converting existing Crown units.

In the translator configuration there are differences in the function of the front
panel, see Section 3 for a description.

Getting Acquainted

1–5

I

1.2.6 Satellator

One additional option is available for all configurations—an FSK Identifier (FSK
IDer). This added feature enables the FM30, FM100, and FM250 to transmit its
call sign or operating frequency in a Morse code style. This option is intended for
use in satellite-fed networks. Transmitters equipped in this fashion are often
known as "satellators."

Connect the transmitter to your satellite receiver and the pre-programmed FSK
IDer does the rest—shifting the frequency to comply with FCC requirements and
in a manner that is unnoticeable to the listener. The FSK IDer module should be
ordered at the time you order your transmitter, but is available separately (factory
programmed for your installation).

Low-pass
Filter

Stereo
Generator

Audio
Processor

®

Illustration 1–4 Transmitter with FSK IDer Option

Add the FSK IDer option to the exciter configuration for the most economical
satellator (a composite input signal is required).

RF Exciter

Metering

RF Out

FM250

1.2.7 Nearcasting

The output power of an FM30 transmitter Can be reduced to a level that could
Function as a near-cast transmitter. Crown transmitters have been used in this
way for language translation, for rebroadcasting the audio of sporting events within
a stadium, and for specialized local radio. The FM30 is the only transmitter that is
appropriate for this application.

1–6

FM30/FM100/FM250 User's Manual

1.3 Transmitter/Exciter Specifications

Frequency Range87.9 MHz–108 MHz (76 MHz–90 MHz

optionally available)

RF Power Output (VSWR 1.5:1 or better)

FM303 - 30 watts, adjustable
FM10010 - 100 watts, adjustable
FM25020 - 250 watts, adjustable

RF Output Impedance 50 Ω
Frequency Stability Meets FCC specifications from

0-50 degrees C

Audio Input Impedance 50 kΩ bridging, balanced, or 600 Ω
Audio Input Level Selectable for –10 dBm to +10 dBm for

75 kHz deviation at 400 Hz

Pre-emphasis Selectable for 25, 50, or 75 µsec; or

Flat

Audio Response Conforms to 75 µsec pre-emphasis

curve as follows

Complete transmitter ±0.30 dB (50 Hz–10 kHz)

±1.0 dB (10 kHz–15 kHz)

Exciter only ±0.25 dB (50 Hz–15 kHz)

Distortion (THD + Noise)

Complete transmitter Less than 0.7% (at 15 kHz)
Exciter only Less than 0.3% (50 Hz–15 kHz)

Stereo Separation

Complete transmitter Better than –40 dB (50 Hz–15 kHz)
Exciter only Better than –40 dB (50 Hz–15 kHz)

Crosstalk Main into sub, better than –40 dB

Sub into main, better than –40 dB

Stereo Pilot 19 kHz ±2 Hz, 9% modulation

Getting Acquainted

1–7

I

Subcarrier Suppression 50 dB below ±75 kHz deviation
FM S/N Ratio (FM noise)

Complete transmitter Better than –60 dB
Exciter only Better than –70 dB

AM S/N Ratio Asynchronous and synchronous noise

better than FCC requirements

RF Bandwidth ±120 kHz, better than –35 dB

±240 kHz, better than –45 dB

RF Spurious Products Better than –70 dB
Operating Environment Temperature (0o C –50o C)

Humidity (0–80% at 20o C)
Maximum Altitude (3,000 meters; 9843

feet)

AC Power 100, 120, 220, or 240 volts (+10%/

–15%); 50/60 Hz
FM30 115 VA
FM100 297 VA
FM250 550 VA

DC Power

FM30 24–36 volts (36 volts at 3 amps required for

full output power)
FM100 and FM250 36–62 volts [48 volts at 5 amps (FM100) or

72 volts at 8 amps (FM250) required for

full output power]

1–8

FM30/FM100/FM250 User's Manual

Note: We set voltage and ampere requirements to assist you in designing your
system. Depending on your operating frequency, actual requirements for maximum
voltage and current readings are 10–15% lower than stated.

Regulatory Type notified for FCC parts 73 and 74

Meets FCC, DOC, and CCIR requirements

Dimensions 13.5 x 41.9 x 44.5 cm

(5.25 x 16.5 x 17.5 inches)

Weight

FM30 10.5 kg (23 lbs)

13.6 kg (30 lbs) shipping weight

FM100 11.4 kg (25 lbs)

14.5 kg (32 lbs) shipping weight

FM250 16.8 kg (37 lbs)

20.0 kg (44 lbs) shipping weight

Getting Acquainted

1–9

I

1.4 Receiver Specifications

Monaural Sensitivity (demodulated, de-emphasized)

3.5 µV for signal-to-noise > 50 dB

Stereo Sensitivity (19–kHz pilot frequency added)

31 µV for signal-to-noise > 50 dB

Connector Standard type N, 50 Ω
Shipping Weight 1 lb

1.5 Safety Considerations

Crown Broadcast assumes the responsibility for providing you a safe product and
safety guidelines during its use. “Safety” means protection to all individuals who
install, operate, and service the transmitter as well as protection of the transmitter
itself. To promote safety, we use standard hazard alert labeling on the product and
in this manual. Follow the associated guidelines to avoid potential hazard.

1.5.1 Dangers

DANGER represents the most severe hazard alert. Extreme bodily harm or death
will occur if DANGER guidelines are not followed.

1.5.2 Warnings

WARNING represents hazards which could result in severe injury or death.

1.5.3 Cautions

CAUTION indicates potential personal injury, or equipment or property damage if
the associated guidelines are not followed. Particular cautions in this text also
indicate unauthorized radio-frequency operation.

Type of Hazard

WARNING

Severe shock hazard!

Pictorial Indication
of Hazard

Turn power off and
wait approximately 1
minute for capacitors
to discharge before
handling them.

Explanation
of Hazard

1–10

Illustration 1–5 Sample Hazard Alert

FM30/FM100/FM250 User's Manual

®

Section 2—Installation

This section provides important guidelines for installing your trans­mitter . Review this information carefully for proper installation.

Installation

2–1

CAUTION

Possible equipment damage!
Before operating the transmitter for

the first time, check for the proper AC
line voltage setting and frequency
selection as described in sections 2.2

and 2.3.

2.1 Operating Environment

You can install the FM transmitter in a standard component rack or on a suitable
surface such as a bench or desk. In any case, the area should be as clean and well­ventilated as possible. Always allow for at least 2 cm of clearance under the unit for
ventilation. If you set the transmitter on a flat surface, install spacers on the
bottom cover plate. If you install the transmitter in a rack, provide adequate
clearance above and below. Do not locate the transmitter directly above a hot piece
of equipment.

2.2 Power Connections

The FM30, FM100, and FM250 operate on 100, 120, 220, or 240 volts AC (50 or 60
Hz; single phase). Each transmitter can operate on DC power as well (28 volts for
the FM30, 36 volts for the FM100, and 62 volts for the FM250). The transmitter
can operate on fewer volts DC, but with reduced RF output power (see section 1.2).
In addition, the transmitter isolates the AC and DC sources; both can be connected
at the same time to provide battery backup in the event of an AC power failure.

2.2.1 AC Line Voltage Setting

To change the voltage setting, follow these steps:

1. Disconnect the power cord if it is attached.

2. Open the cover of the power connector assembly using a small, flat blade
screwdriver . See Illustration 2–1.

3. Insert the screwdriver into the voltage selection slot and remove the drum
from the assembly.

4. Rotate the drum to select the desired voltage. See Illustration 2–2.

5. Replace the drum and cover and check to see that the correct voltage appears
in the connector window.

6. Connect the AC power cord.

2–2

FM30/FM100/FM250 User's Manual

120Vac

Illustration 2–1 Removing the Power Connector Cover

Installation

remove drum

before turn

120Vac

220Vac
240Vac

Illustration 2–2 Selecting an AC Line Voltage

2–3

2.2.2 Fuses

The fuse holders are located in the power connector assembly just below the voltage
selector .

120Vac

220Vac
240Vac

remove drum

before turn

Illustration 2–3 Fuse Holder

For 100 to 120 VAC operation, use the fuse installed at the factory. For 220 to 240
VAC operation, use the slow-blow fuse located in a hardware kit within the
transmitter packaging. Consult the following table:

Transmitter Input Power Fuse

FM30 100–120 V 3 A

220–240 V 1.5 A

FM100 100–120 V 6.3 A

220–240 V 4 A

FM250 100–120 V 12.5 A

220–240 V 6.3 A

Illustration 2–4 Fuse Reference Table

2–4

FM30/FM100/FM250 User's Manual

2.2.3 Battery Power

Your transmitter can operate on a DC power source (such as 3 or 4, 12–volt auto­motive batteries connected in series). The FM30 requires 28 volts DC for full
output power , while the FM100 requires 36 volts, and FM250 requires 62 volts for
full output power. Connect the batteries to the red (+) and black (–) battery input
binding posts on the rear panel.

SCA IN

1

23

COMPOSITE IN

R

MONITOR

REMOTE I/O

RIGHT

L

CIRCUIT
BREAKER

OFF

LEFT/MONO

+

–

36 VDC

B
A
T
T
E
R
Y

Illustration 2–5 DC Input Terminals

CAUTION

Possible equipment damage!
Never connect a battery charger to the

input terminals of the transmitter
unless a battery is also connected.
Voltage peaks from a typical charger
(without the load of a battery) can be
destructive to the transmitter.

DC Input Terminals

2.3 Frequency (Channel) Selection

You may select an operating frequency of 87 to 108 MHz in the FM broadcast band.
Pins 9 and 10 of HD2 on the RF Exciter board are jumpered for frequencies

other than these such as the optional Japan frequencies of 76-90 MHz.

T o adjust the operating frequency, follow these steps:

1.Remove the top cover by removing 18 screws.

Installation

2–5

2. Locate the RF Exciter board and identify the frequency selector switches
which will be used to change the setting. See Illustrations 2–6 and 2–7.

Modulation
Trim-pot

RF Exciter

®

Illustration 2–6 Top Cover Removed

Frequency Selection
Rotary Switches

FM250

OPTIONAL

MEGAHERTZ

.1 .01

Illustration 2–7 RF Exciter Board (Frequency Selector Switches)

3. Use small flat blade screwdriver or another suitable device to rotate the
switches to the desired setting. (The selected number will appear directly
above the white indicator dot on each switch.) See examples of selected
frequencies in the illustration below.

= 88.1 MHz

= 107.9 MHz

Illustration 2–8 Two Sample Frequency Selections

2–6

FM30/FM100/FM250 User's Manual

2.3.1 Modulation Compensator

The Modulation trim-potentiometer (see illustration 2–6) compensates for slight
variations in deviation sensitivity with frequency. Set the trim-pot dial according to
the following graph:

Modulation Compensation Pot Setting

90

80

70

60

50

40

30

20

10

0

75 80 85 90 95 100 105 110

Frequency (MHz)

Illustration 2–9 Modulation Compensator Settings

These compensator settings are approximate. Each mark on the potentiometer
represents about 1.8% modulation compensation. For more exact settings, refer to
section 5.2.2.

Installation

2–7

2.4 Receiver Frequency Selection

If you have a transmitter equipped with the receiver option, you will need to set the
receiving or incoming frequency.

1. With the top cover removed, locate the receiver module and the two switches
(labeled SW1 and SW2).

Frequency Selection Switches

Receiver
Module

®

FM250

Illustration 2–10 Receiver Module Switches

2. Use the adjacent chart to set the switches for the desired incoming frequency.

3.After setting the frequency, replace the top cover and screws.

2–8

FM30/FM100/FM250 User's Manual

Frequency SW1 SW2

87.9 0 0

88.0 80

88.1 0 1

88.2 8 1

88.3 0 2

88.4 8 2

88.5 0 3

88.6 8 3

88.7 0 4

88.8 8 4

88.9 0 5

89.0 85

89.1 0 6

89.2 8 6

89.3 0 7

89.4 8 7

89.5 0 8

89.6 8 8

89.7 0 9

89.8 8 9

89.9 0 A

90.0 8A

90.1 0 B

90.2 8 B

90.3 0 C

90.4 8 C

90.5 0 D

90.6 8 D

90.7 0 E

90.8 8 E

90.9 0 F

91.0 8F

91.1 1 0

91.2 9 0

91.3 1 1

91.4 9 1

91.5 1 2

91.6 9 2

91.7 1 3

91.8 9 3

91.9 1 4

92.0 94

92.1 1 5

92.2 9 5

92.3 1 6

92.4 9 6

92.5 1 7

92.6 9 7

92.7 1 8

92.8 9 8

92.9 1 9

Frequency SW1 SW2

93.0 99

93.1 1 A

93.2 9 A

93.3 1 B

93.4 9 B

93.5 1 C

93.6 9 C

93.7 1 D

93.8 9 D

93.9 1 E

94.0 9E

94.1 1 F

94.2 9 F

94.3 2 0

94.4 A 0

94.5 2 1

94.6 A 1

94.7 2 2

94.8 A 2

94.9 2 3

95.0 A3

95.1 2 4

95.2 A 4

95.3 2 5

95.4 A 5

95.5 2 6

95.6 A 6

95.7 2 7

95.8 A 7

95.9 2 8

96.0 A8

96.1 2 9

96.2 A 9

96.3 2 A

96.4 A A

96.5 2 B

96.6 A B

96.7 2 C

96.8 A C

96.9 2 D

97.0 AD

97.1 2 E

97.2 A E

97.3 2 F

97.4 A F

97.5 3 0

97.6 B 0

97.7 3 1

97.8 B 1

97.9 3 2

Frequency SW1 SW2

98.0 B2

98.1 3 3

98.2 B 3

98.3 3 4

98.4 B 4

98.5 3 5

98.6 B 5

98.7 3 6

98.8 B 6

98.9 3 7

99.0 B7

99.1 3 8

99.2 B 8

99.3 3 9

99.4 B 9

99.5 3 A

99.6 B A

99.7 3 B

99.8 B B

99.9 3 C

100.0 BC

100.1 3 D

100.2 B D

100.3 3 E

100.4 B E

100.5 3 F

100.6 B F

100.7 4 0

100.8 C 0

100.9 4 1

101.0 C1

101.1 4 2

101.2 C 2

101.3 4 3

101.4 C 3

101.5 4 4

101.6 C 4

101.7 4 5

101.8 C 5

101.9 4 6

102.0 C6

102.1 4 7

102.2 C 7

102.3 4 8

102.4 C 8

102.5 4 9

102.6 C 9

102.7 4 A

102.8 C A

102.9 4 B

Frequency SW1 SW2

103.0 CB

103.1 4 C

103.2 C C

103.3 4 D

103.4 C D

103.5 4 E

103.6 C E

103.7 4 F

103.8 C F

103.9 5 0

104.0 D0

104.1 5 1

104.2 D 1

104.3 5 2

104.4 D 2

104.5 5 3

104.6 D 3

104.7 5 4

104.8 D 4

104.9 5 5

105.0 D5

105.1 5 6

105.2 D 6

105.3 5 7

105.4 D 7

105.5 5 8

105.6 D 8

105.7 5 9

105.8 D 9

105.9 5 A

106.0 DA

106.1 5 B

106.2 D B

106.3 5 C

106.4 D C

106.5 5 D

106.6 D D

106.7 5 E

106.8 D E

106.9 5 F

107.0 DF

107.1 6 0

107.2 E 0

107.3 6 1

107.4 E 1

107.5 6 2

107.6 E 2

107.7 6 3

107.8 E 3

107.9 6 4

108.0 E4

Installation

Illustration 2–11 Receiver Frequency Selection

2–9

2.5 RF Connections

Connect the RF load, an antenna or the input of an external power amplifier , to the
type-N, RF output connector on the rear panel. VSWR should be 1.5:1 or better.

WARNING

Severe shock hazard!
Do not touch the inner

portion of the RF
output connector
when transmitter
power is on.

The RF monitor is intended primarily for a modulation monitor connection.
Information gained through this connection can supplement that which is available
on the transmitter front panel displays.

If your transmitter is equipped with the receiver option, connect the incoming RF
to the RF IN connector.

RF Output
Connector

RF Output
Monitor

RF Input Connector
(receiver option only)

120Vac

Illustration 2–12 RF Connections

2–10

FM30/FM100/FM250 User's Manual

2.6 Audio Input Connections

Attach audio inputs to the Left and Right XLR connectors on the rear panel. (The
Left channel audio is used on Mono.) Pin 1 of the XLR connector goes to chassis
ground. Pins 2 and 3 represent a balanced differential input with an impedance of
about 50 kΩ. They may be connected to balanced or unbalanced left and right
program sources.

The audio input cables should be shielded pairs, whether the source is balanced or
unbalanced. For an unbalanced program source, one line (preferably the one
connecting to pin 3) should be grounded to the shield at the source. Audio will
then connect to the line going to pin 2.

SCA IN

1

23

COMPOSITE IN

R

MONITOR

REMOTE I/O

RIGHT

L

LEFT/MONO

Audio Inputs

B

+

CIRCUIT
BREAKER

OFF

A
T
T
E
R
Y

–

36 VDC

Illustration 2–13 XLR Audio Input Connectors

By bringing the audio return line back to the program source, the balanced
differential input of the transmitter is used to best advantage to minimize noise.
This practice is especially helpful if the program lines are fairly long, but is a good
practice for any distance.

If the program source requires a 600 Ω termination, see the motherboard

configuration chart on page 6-14 for the proper configuration of the jumpers.

Installation

2–11

2.7 SCA Input Connections

You can connect external SCA generators to the SCA In connectors (BNC-type) on
the rear panel. The inputs are intended for the 60 kHz to 99 kHz range, but a lower
frequency may be used if the transmitter is operated in Mono mode. (The 23 to 53
kHz band is used for stereo transmission.) For 7.5 kHz deviation (10%
modulation), input of approximately 3.5–volts (peak-to-peak) is required.

SCA IN

1

23

COMPOSITE IN

R

MONITOR

REMOTE I/O

RIGHT

L

LEFT/MONO

SCA Inputs

B

+

CIRCUIT
BREAKER

OFF

A
T
T
E
R
Y

–

36 VDC

Illustration 2–14 SCA Input Connectors

2.8 Composite Input Connection

You may feed composite stereo (or mono audio) directly to the RF exciter, bypassing
the internal audio processor and stereo generator . To use the Crown transmitter as
an RF Exciter only ("E" version or when using the "T" version with composite
input), it is necessary to use the Composite Input section of the transmitter. This
will feed composite stereo (or mono audio) directly to the RF exciter . In the "T"
version, this will bypass the internal audio processor and stereo generator.

Input sensitivity is approximately 3.5–volt P-P for 75 kHz deviation.

1. Enable the Composite Input by grounding pin 9 of the Remote I/O

connector (see Illustration 2–17).

2. Connect the composite signal using the Composite In BNC connector .

2–12

FM30/FM100/FM250 User's Manual

Composite In
BNC Connector

SCA IN

1

23

COMPOSITE IN

R

MONITOR

REMOTE I/O

RIGHT

L

CIRCUIT
BREAKER

OFF

LEFT/MONO

+

–

36 VDC

B
A
T
T
E
R
Y

Audio Monitor Jacks

Illustration 2–15 Composite In and Audio Monitor Connections

2.9 Audio Monitor Connections

Processed, de-emphasized samples of the left and right audio inputs to the stereo
generator are available at the Monitor jacks on the rear panel. The signals are
suitable for feeding a studio monitor and for doing audio testing. De-emphasis is
normally set for 75 µsec; set to 50 µsec by moving jumpers, JP203 and JP204, on
the Stereo Generator board.

2.10 Pre-emphasis Selection

Select the pre-emphasis curve (75 µsec, 50 µsec, 25 µsec, or Flat) by jumpering the
appropriate pins of header JP1 on the audio processor board. If you change the pre­emphasis, change the de-emphasis jumpers JP203 and JP204 on the Stereo
Generator board to match.

Installation

2–13

2.11Program Input Fault Time-out

You can enable an automatic turn-off of the carrier in the event of program failure.
To enable this option, see illustration 2-17 on page 2-15. The time between program
failure and carrier turn-off is set by a jumper (JP1) on the voltage regulator board
(see page 6–17 for board location). Jumper pins 1 and 2 (the two pins closest
to the edge of the board) for a delay of approximately 30 seconds; pins 3 and 4 for a
2–minute delay; pins 5 and 6 for a 4–minute delay, and pins 7 and 8 for an 8–
minute delay.

2.12 Remote I/O Connector

Remote control and remote metering of the transmitter is made possible through a
15–pin, D-sub connector on the rear panel. (No connections are required for
normal operation.)

Remote I/O

SCA IN

1

23

COMPOSITE IN

R

MONITOR

REMOTE I/O

RIGHT

L

CIRCUIT
BREAKER

OFF

LEFT/MONO

+

–

36 VDC

B
A
T
T
E
R
Y

Illustration 2–16 Remote I/O Connector

Illustration 2-17 on page 2-15 summarizes the Remote I/O pin connections.

2–14

FM30/FM100/FM250 User's Manual