Model MFJ-618
VERSION 1A
INSTRUCTION MANUAL
CAUTION: Read All Instructions Before Operating Equipment
MFJ ENTERPRISES, INC.
300 Industrial Park Road
Starkville, MS 39759 USA
Tel: 662-323-5869 Fax: 662-323-6551
COPYRIGHT 2007 MFJ ENTERPRISES, INC.
C
DISCLAIMER
Information in this manual is designed for user purposes only and is not
intended to supersede information contained in customer regulations, technical
manuals/documents, positional handbooks, or other official publications. The
copy of this manual provided to the customer will not be updated to reflect
current data.
Customers using this manual should report errors or omissions,
recommendations for improvements, or other comments to MFJ Enterprises, 300
Industrial Park Road, Starkville, MS 39759. Phone: (662) 323-5869; FAX: (662)
323-6551. Business hours: M-F 8-4:30 CST.
MFJ-618 Dual Channel Speech Intelligibility Enhancer
TM
Instruction & Technical Manual
TABLE OF CONTENTS
TOPIC PAGE
1. TABLE OF CONTENTS 2
2. LIST OF FIGURES 2
3. INTRODUCTION AND FEATURES 3
4. TYPICAL SPECIFICATIONS 4
5. SYSTEM CONTROLS AND INDICATORS 5
a. FRONT PANEL CONTROLS AND INDICATORS 5
b. REAR PANEL CONTROLS AND INDICATORS 6
6. SYSTEM SETUP 7
a. INTERNAL HEADERS 7
b. INTERNAL JUMPER BLOCKS 7
c. CABLES 7
d. POWER 8
e. HEADPHONES 8
f. RADIO AUDIO 8
7. THEORY OF OPERATION 9
8. MFJ-618 EASY-START INSTRUCTIONS 11
9. IN CASE OF DIFFICULTY 17
10.TECHNICAL ASSISTANCE 17
LIST OF FIGURES
Figure 1 Front Panel Jacks and Controls 5
Figure 2 Rear Panel Jacks and Controls 6
Figure 3 Power Hook-up 7
Figure 4 Headphone Hook-up 7
Figure 5 Speaker Hook-up 8
Figure 6 Internal Headers 9
Figure 7 Block Diagram 10
Figure 8 Operational Diagram 11
Figure 9 Schematic Main Board 15
Figure 10 Schematic Daughter Board 16
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MFJ-618 Dual Channel Speech Intelligibility Enhancer
TM
Instruction & Technical Manual
INTRODUCTION & FEATURES
INTRODUCTION
The MFJ-618 Dual Channel Speech Intelligibility EnhancerTM is a powerful
communication tool that surrounds your operating position with crystal-clear
electronically-enhanced audio. It also puts the fun back into ham radio! Here are
some of the high-tech features we think you'll enjoy:
Studio Quality: The Dual Channel Speech Intelligibility EnhancerTM is designed
to drive two identical high quality speakers installed three or more feet apart.
This configuration improves intelligibility, enhances frequency response, and
dramatically increases spatial presence. Once your system is set up, you'll think
you're in a broadcast studio!
Dual Channel Speech Intelligibility EnhancerTM: Every radio has different
audio characteristics--and everyone's hearing response changes over time. Our
exclusive Dual Channel Speech Intelligibility EnhancerTM tailors the sound of your
radio especially for your ears. Young or old, you'll hear more clearly than ever
before!
Dual Amplifiers: Two powerful monolithic IC amplifiers deliver deep, rich,
undistorted audio to high quality, hi-fidelity speakers (not supplied).
Dual Equalizer: Two independent equalizers allow you to adjust the Right and
Left Channel of Audio to your preference.
Expansion: At the push of a button you can easily invert the audio of the Left
Channel to really make the signal jump out at you. Extremely useful in marginal
conditions.
Adjustable Balance: A front-panel Balance control aligns speakers for dead-
center positioning regardless of speaker placement or differences in ear
sensitivity.
Easy-to-Operate: Conveniently placed knobs, easy-to-access switches, and a
wide-open panel layout make the MFJ-618 very easy to set up and use.
Dual Input A/B: Switch between radios with the push of a button--no messing
with patch cables behind the desk.
TM
By-Pass Function: Switch Dual Channel Speech Intelligibility Enhancer
in or
out without cutting off the speakers. This feature is especially helpful for sound
comparisons during the frequency set-up.
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MFJ-618 Dual Channel Speech Intelligibility Enhancer
TM
Instruction & Technical Manual
INTRODUCTION & FEATURES
Multiple Outputs: Choose individual 3.5mm monaural jacks or a stereo jack
wired for computer-style speakers. Also, a front panel switch turns off your Left
Channel speakers, the stereo headset stays active. Front panel phone jack is
attenuated to headset levels (deactivated with internal jumpers).
Multiple Power Sources: Use transceiver's 13.8-volt supply, wall adapter,
dedicated supply, or 12-volt battery to power your unit.
Rugged Construction: Attractive all-metal cabinet, conservative component
selection, and space-age SMD circuitry ensure solid performance for years to
come. Fully covered by MFJ's "No Matter What" one year limited warranty.
Before attempting to operate your MFJ-618, please read this manual thoroughly.
It contains important details you'll need to know to obtain the best performance
from your unit.
Typical Specifications
Input Sources....................2, switched
Source Level.....................Line
Input Load.........................500 Ohms resistive
Frequency Range..............300, 600, 1200, 2400 Hz center
Overall Response..............100-5000 Hz
Channels Out....................2, bridged balance control
Power Output....................3 watts per channel into 4 Ohms
Power Requirement ..........12-15 Vdc @ 1.5Amp
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MFJ-618 Dual Channel Speech Intelligibility Enhancer
A
TM
Instruction & Technical Manual
SYSTEM CONTROLS AND INDICATORS
MFJ-618 CONTROLS AND INDICATORS
FRONT PANEL
Dual Channel
Speech Intelligibility Enhancer
EXPANSION
ON
VOLUME BALANCE
OFF
BYPASS
300Hz 600Hz 1200Hz 2400Hz
LEFT
RIGHT
B
INPUT A / B
ON
OFF
SPEAKER PHONES POWER
ON
OFF
Figure 1: MFJ-618 Front Panel Jacks and Controls
1. Volume: Adjusts overall loudness of both channels.
2. Expansion: Expands apparent listening field.
3. Bypass: Turns Speech Intelligibility EnhancerTM function on and off for
comparative listening.
4. Balance: Establishes central balance between right and left speakers.
5. Input A/B: Selects between two sources.
6. 300 Hz: Cuts or emphasizes lowest speech frequencies on the left channel.
7. 300 Hz: Cuts or emphasizes lowest speech frequencies on the right channel.
8. Speaker: Disables speakers--used when monitoring with headphones.
9. 600 Hz: Cuts or emphasizes mid-range speech frequencies on the left channel.
10. 600 Hz: Cuts or emphasizes mid-range speech frequencies on the right channel.
11. Phones: Accepts 1/4" stereo headphone plug, normally attenuated for phones
(attenuation deactivated internally).
12. 1200 Hz: Cuts or emphasizes upper-range speech frequencies on the left channel.
13. 1200 Hz: Cuts or emphasizes upper-range speech frequencies on the right channel.
14. Power: Selects between unamplified and amplified signals.
15. 2400 Hz: Cuts or emphasizes syllabant sounds and adjacent "chatter" on the left
channel.
16. 2400 Hz: Cuts or emphasizes syllabant sounds and adjacent "chatter" on the right
channel.
MODEL
MFJ-618
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