Crown FM500 User Manual

Revision Control

Revision Print Date

Initial Release (K80713–9) June 1996
Revision 1 (101033–1) November 1996
Revision 2 (101033–2) August 1997
Revision 3 (900239–1) February 1998
Revision 4 (900239–1) October 1998
Revision 5 (901047-1) October 1999
Revision 6 (901047-2) May 2000
Revision 7 March 2002

Revision 8 February 2006

Important Notices

©2006, 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.
Sony and RCA are trademarks of their respective companies.
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

1.3 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 Remove PA Tray Spacers ..................................................................................2–2

2.3 Power Connections ...........................................................................................2–3

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

2.4.1 Modulation Compensator..............................................................................2–6

2.4.2 RF T uning Adjustments.................................................................................2–7

2.5 Receiver Frequency Selection............................................................................2–7

2.6 RF Connections.................................................................................................2–9

2.7 Audio Input Connections .................................................................................2–10

2.8 SCA Input Connections ...................................................................................2–11

2.9 Composite Input Connection ........................................................................... 2–11

2.10 Audio Monitor Connections.............................................................................2–12

2.11 Pre-emphasis Selection...................................................................................2–12

2.12 Processor Bypass Option ................................................................................2–12

2.13 Program Input Fault Time-out .........................................................................2–13

2.14 Remote I/O Connector.....................................................................................2–13

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

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

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

3.4 Input Gain Switches ..........................................................................................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 Boards ......................................................................4–12

4.10 RF Driver.........................................................................................................4–12

4.11 RF Amplifier ....................................................................................................4–13

4.12 Chassis ...........................................................................................................4–13

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

4.15 Receiver Circuit Board Option .........................................................................4–14

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 ..........................................................................5–3

5.2.1 Separation ....................................................................................................5–3

5.2.2 Composite Output.........................................................................................5–3

5.2.3 19 kHz Level .................................................................................................5–3

5.2.4 19 kHz Phase................................................................................................5–3

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 .....................................................................................5–4

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 ...........................................................................................5–5

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)...........................................................................5–6

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

Appendix................................................................ A–1

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

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

I

INFORMATION

Section 1—Getting Acquainted

This section provides a general description of the FM500 trans­mitter 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 FM500 is a member of a family of FM stereo broadcast transmitters. Crown
transmitters are known for their modularity, ease-of-use, and reliability.

The modularity 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 four rotary
switches), add an audio source, attach an antenna, connect AC 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.

Audio Input

High

-12

-18
Low

Modulation

10

2

High Band

Expand

Compress

2

-6

Wide Band

+6 dB

20

+12 dB

ProcessingInput Gain

®

RF Power
SWR
ALC
PA DC Volts
PA DC Amps
PA Temperature
Supply DC Volts
Voltmeter

Fault

SWR
Lock
Input
PA DC
PA Temp

Stereo

Mono RF Output

Carrier

Over
100
90
80
70
60

Power

50
40
30
20
Pilot

FM500

FM BROADCAST TRANSMITTER

Illustration 1–1 FM500 Stereo Broadcast Transmitter

1–2

FM500 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, and satellator
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
FM500, for example, can generate up to 500 watts of RF output power.

Suffix letters describe the configuration. The FM500T, for example, designates a
"transmitter" configuration. Since this is standard, it is what is described in the
manual except where specified. In this configuration, the product includes the
following modules (functions):

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

Stereo Generator

Audio Processor

Audio Input

10

High

-6

-12

-18
Low

2

Wide Band

+6 dB

Expand

Compress

20

+12 dB

ProcessingInput Gain

®

2

High Band

RF Power
SWR
ALC
PA DC Volts
PA DC Amps
PA Temperature
Supply DC Volts
Voltmeter

Fault

SWR
Lock
Input
PA DC
PA Temp

Stereo

Mono RF Output

Over
100
90
80
70
60

Power

50
40
30
20
Pilot

FM500

FM BROADCAST TRANSMITTER

Carrier

Modulation

Illustration 1–2 Standard (Transmitter) Configuration

RF Exciter

Low-pass Filter

Metering

Getting Acquainted

1–3

I

1.2.1 Stand-Alone

In the standard configuration, the FM500 is an ideal stand-alone transmitter.
When you add an audio source (monaural, L/R stereo, or composite signal), an
antenna, and AC 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.

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 FM500 is available in optional
configurations to meet a variety of needs.

An "E" suffix, as in the FM500E, for example, represents an exciter-only configura­tion. In this configuration, the audio processor and stereo generator are not
included. The exciter configurations are the least expensive way to get Crown­quality 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

FM500 User's Manual

1.2.5 Translator

A receiver configuration (FM500R, for example) takes an exciter configuration and
adds receiver circuitry as well. This added feature makes the FM500 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

RF IN

Low-pass Filter

RF Out

(option)

Stereo
Generator

RF Exciter

Metering

Audio Input

10

High

-6

-12

-18
Low

Expand

Compress

2

20

Wide Band

+12 dB

+6 dB

ProcessingInput Gain

®

2

High Band

RF Power
SWR
ALC
PA DC Volts
PA DC Amps
PA Temperature
Supply DC Volts
Voltmeter

Fault

SWR
Lock
Input
PA DC
PA Temp

Stereo

Mono RF Output

Over
100
90
80
70
60

Power

50
40
30
20
Pilot

FM500

FM BROADCAST TRANSMITTER

Carrier

Modulation

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.

Getting Acquainted

1–5

I

1.2.6 Satellator

Another option is available for all configurations—an FSK Identifier (FSK IDer).
This added feature enables the FM500 to transmit its call sign or operating fre­quency in Morse Code. 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).

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

FSK IDer
(option)

Low-pass Filter

Stereo
Generator

RF Exciter

Audio

Audio Input

High

-6

-12

-18
Low

Processor

2

High Band

Expand

Compress

2

Wide Band

+12 dB

+6 dB

ProcessingInput Gain

10

20

®

Metering

RF Power
SWR
ALC
PA DC Volts
PA DC Amps
PA Temperature
Supply DC Volts
Voltmeter

Fault

SWR
Lock
Input
PA DC
PA Temp

Stereo

Mono RF Output

Modulation

Over
100
90
80
70
60
50
40
30
20
Pilot

FM500

FM BROADCAST TRANSMITTER

Illustration 1–4 Transmitter with FSK IDer Option

RF Out

Carrier

Power

1–6

FM500 User's Manual

1.3 Transmitter/Exciter Specifications

Frequency Range 87 MHz–108 MHz (65 MHz–73 MHz

optionally available)

RF Power Output 100–550 watts (VSWR 1.5:1 or better)
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
Subcarrier Suppresion 50 dB below ±75 kHz deviation
FM S/N Ratio (FM noise)

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

Getting Acquainted

1–7

I

AM S/N Ratio Asynchronous and synchronous noise

better than NAB recommendations

RF Bandwidth ±120 kHz, better than –35 dB

±240 kHz, better than –45 dB

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

Regulatory Type notified for FCC parts 73 and 74;

Meets FCC, DOC, and CCIR requirements

Dimensions 17.8 x 41.9 x 44.5 cm

(7.0 x 16.5 x 17.5 inches)

Weight 29.5 kg (65 lbs);

31.8 kg (70 lbs) shipping weight

1–8

FM500 User's Manual

1.4 Receiver Specifications

Monaural Sensitivity (demodulated, de-emphasized)

3.5 µV for signal-to-noise > 50 dB

12.6 µV for signal-to-noise > 60 dB

Stereo Sensitivity (19–kHz pilot frequency added)

2.8 µV for signal-to-noise > 40 dB
8 µV for signal-to-noise > 50 dB
31 µV for signal-to-noise > 60 dB

Connector Standard type N, 50 Ω
Shipping Weight 1 lb

Getting Acquainted

1–9

I

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.

Pictorial Indication
of Hazard

WARNING

Severe shock hazard!
Turn power off and

wait approximately 1
minute for capacitors
to discharge before
handling them.

Illustration 1–5 Sample Hazard Alert

Type of Hazard

Explanation of
Hazard

1–10

FM500 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 2.3

and 2.4.

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 Remove PA Tray Spacers

The Crown FM 500 is shipped with spacers between the PA tray and the transmitter
back panel. The spacers prevent damage to internal contacts during shipping.
Remove and save the spacers and screws before installing the FM500.

#8

#8

#6

Illustration 2-1 FM 500 PA Tray Mounting Screws

1. Remove screws and spacers from five locations.

2. Firmly push the PA tray into the FM 500 until the PA tray panel touches the
back panel.

3. Locate the bag labeled 500 Hardware. Install four #8 screws and washers and
one number #6 screw and washer. See photo for locations.

2–2

FM500 User's Manual

2.3 Power Connections

The FM500 operates on 100, 120, 220, or 240 volts AC (50 or 60 Hz; single phase).
As shipped (factory default settings), the FM500 operates on 120 volts at 60 Hz.

If you are operating the transmitter at 120 volts you do not need to make any
changes. To operate the FM500 at 100, 220, or 240 volts, a few changes are
necessary.

To change the voltage setting, follow these steps:

1. Disconnect the power cord if it is attached.

2. To set the input voltage for 100 volts, skip to step 7.

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

4. Insert the screwdriver into the top slot of the voltage selection assembly
(red) and pry out the assembly from the power connector.

5. If you are setting the input voltage for 220 or 240 volts, replace the installed
fuses with 12 amp fuses (included in your package). See Illustration 2–3.

6. Replace the red fuse assembly so that the "230V" setting appears right side up
in the window. Close the assembly window.

115V

Illustration 2–2

Opening the Power Connector Cover

Installation

115V

230V

Illustration 2–3

Removing the Voltage Selection (red) Assembly

2–3

7. Turn the transmitter upside down and remove the bottom cover.

Note: The front panel filter grill must be removed to expose all of the bottom

Power
Distribution
Board

front of transmitter

Illustration 2–4 Underside of Transmitter—Bottom Cover Removed

cover screws for bottom cover removal and installation.

8. Locate the power distribution circuit board on the left side next to the large
transformer cover. See Illustration 2–4.

9. For 100 or 220 volt operation, change the jumper setting of P1 to the 100/
220 V setting.

10. For 220 or 240 volt operation,

• remove the jumper connecting P6 and P7.

• remove the jumper connecting P4 and P5.

• use a jumper to connect P5 and P6.

11. Replace the bottom cover, and the front grill.

12. Connect the AC power cord.

For your reference, use 12 amp fuses for 220 or 240 volt operation and 20 amp
fuses for 100 or 120 volt operation.

2–4

FM500 User's Manual

2.4 Frequency (Channel) Selection

You may select an operating frequency of 87 to 108 MHz in the FM broadcast band
with 100 kHz channel spacing (10 kHz spacing is optional with the addition of a
fifth rotary selector switch).

To adjust the operating frequency, follow these steps:

1. Remove the top cover by removing 15 screws.

2. Locate the RF Exciter board and identify the frequency selector switches
which will be used to change the setting. See Illustrations 2–5 and 2–6.

Modulation
Trim-pot

Audio Input

Frequency Selection
Rotary Switches

RF Exciter

10

High

-6

-12

-18
Low

2

+6 dB

Wide Band

Expand

Compress

20

+12 dB

ProcessingInput Gain

®

2

High Band

RF Power
SWR
ALC
PA DC Volts
PA DC Amps
PA Temperature
Supply DC Volts
Voltmeter

Fault

SWR
Lock
Input
PA DC
PA Temp

Stereo

Mono RF Output

Over
100
90
80
70
60

Power

50
40
30
20
Pilot

FM500

FM BROADCAST TRANSMITTER

Carrier

Modulation

Illustration 2–5 Top Cover Removed

Illustration 2–6 RF Exciter Board Frequency Selector Switches

Installation

MEGAHERTZ

.1 .01

2–5

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 2–7 Two Sample Frequency Selections

4. If you have the receiver option, proceed to section 2.5 to set the incoming
frequency. Otherwise, replace the top cover.

2.4.1 Modulation Compensator

The Modulation trim-potentiometer (see illustration 2–8) 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 2–8 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.

2–6

FM500 User's Manual

2.4.2 RF Tuning Adjustments

All the RF stages are broadband to cover the 88 to 108 MHz broadcast band. The
RF amplifier stages require no tuning.

2.5 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).

2. Use the table on the following pages to set the switches for the desired
incoming frequency.

3. After setting the frequency, return to section 2.3.1 to set the modulation
compensator.

Frequency Selection
Switches SW1 & SW2

Stereo

Receiver

Generator

Module

Audio Input

High

-6

-12

-18
Low

2

High Band

Expand

Compress

2

Wide Band

+12 dB

+6 dB

Processing

Input Gain

Illustration 2–8 Receiver Module Switches

RF IN

RF Exciter

Carrier

Modulation

10

20

®

RF Power
SWR
ALC
PA DC Volts
PA DC Amps
PA Temperature
Supply DC Volts
Voltmeter

Fault

SWR
Lock
Input
PA DC
PA Temp

Stereo

Mono

RF Output

Over
100
90
80
70
60

Power

50
40
30
20
Pilot

FM500

FM BROADCAST TRANSMITTER

Installation

2–7

Frequency S W1 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

2–8

Table 2–1 Receiver Frequency Selection

FM500 User's Manual

2.6 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

RFInput Connector
(receiver option only)

115V

Illustration 2–10 RF Connections

Installation

2–9

2.7 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

Illustration 2-10 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, install resistors on the 8–pin
DIP socket on the motherboard (socket A501 located between the XLR
connectors). See the motherboard schematic, on page 6–13.

2–10

FM500 User's Manual

2.8 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
(BNC) Connectors

Illustration 2–12 SCA Input Connectors

2.9 Composite Input Connection

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. See Section 2.12 on the next page for caution in using the
bypass option.

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 2–15).

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

Installation

2–11

SCA IN

1

23

COMPOSITE IN

R

MONITOR

REMOTE I/O

RIGHT

L

LEFT/MONO

Composite Input
(BNC) Connector

Audio Monitor
(RCA) Jacks

Illustration 2–13 Composite In and Audio Monitor Connections

2.10 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.

2.11 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
pre-emphasis, change the de-emphasis jumpers JP203 and JP204 on the Stereo
Generator board to match.

2.12 Processor Bypass Option

You may bypass the audio processor in order to feed the left and right (pre­emphasized) audio directly to the stereo generator. The Normal-Bypass slide
switch is near the left-rear corner of the motherboard. If the audio source is
already processed and you do not desire further processing, use the Normal mode
but turn the Processing control (on the front panel) to “0.” (See also section 3.5.)

CAUTION

In the BYPASS position, the pre-emphasis circuits and the filters that protect the
pilot and stereo subcarrier are bypassed. As a result, the occupied bandwidth
specifications of the transmitter could be compromised. The 15–Hz high-pass
filters are also bypassed which may mean that modulation with frequencies
below 10 Hz could cause the frequency synthesizer to unlock.

2–12

FM500 User's Manual

2.13 Program 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 the table on the next page. The time between program
failure and carrier turn-off is set by a jumper (JP701) on the voltage regulator
board (see Illustration 6–4 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.

2.14 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.)

SCA IN

1

23

COMPOSITE IN

MONITOR

R

REMOTE I/O

RIGHT

L

Remote I/O

Illustration 2–14 Remote I/O Connector

The following table summarizes the Remote I/O pin connections.

LEFT/MONO

Installation

2–13

Pin Number Function

1 Ground
2 (no connection)
3 Composite Out (sample of stereo generator output)
4 FSK In (Normally high; pull low to shift carrier

frequency approximately 7.5 kHz. Connect to open
collector or relay contacts of user-supplied FSK keyer.)

5 /Auto Carrier Off (Pull low to enable automatic turnoff

of carrier with program failure.)
6 Meter Battery (unregulated DC volts; 5 volts = 50 VDC)
7 Meter RF Watts (1 volt = 100 watts)
8 Meter PA Volts (5 volts = 50 VDC)
9 /Ext. Enable (Pull low to disable internal stereo

generator and enable External Composite Input.)
10 a) 38 kHz Out (From stereo generator for power supply

synchronization.)

b) For transmitters equipped with tuner option, this pin

becomes the right audio output for an 8–ohm monitor

speaker. 38kHZ Out is disabled.
11 ALC
12 /Carrier Off (pull low to turn carrier off.)
13 Fault Summary (line goes high if any fault light is

activated.)
14 Meter PA Temperature (5 volts = 100 degrees C.)
15 Meter PA Current (1 volt = 10 amperes DC.)

Table 2–3 Remote I/O Connections

8

15

1

9

Illustration 2–15 Remote I/O Connector (outside view)

2–14

FM500 User's Manual