MFJ MFJ-434B User Manual

MFJ-434B Instruction Manual Voice Keyer
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INTRODUCTION
The MFJ-434B was designed by contesters and optimized to perform under the toughest
operating conditions. You don't need to be a contest superstar to appreciate what the MFJ-434B
can do. Even casual operators will discover the MFJ-434B is packed with user-friendly features
that make operating, both in and out of contests, more enjoyable and fun. Set it up, and you'll be
amazed how quickly it becomes part of your operating routine.
Before you begin, please read this manual thoroughly. It contains important information you'll
need to know before attempting to interface the MFJ-434B with your transceiver. We'll start
with a brief introduction to the special features that make your Voice Keyer an important
addition to any station, and an absolute necessity for any serious contest station:
Easy Selection: Large soft-touch switches select up to five pre-recorded messages.
Big Memory: Up to 75 seconds accumulated storage.
Dual Front Panel Microphone Connectors: Connect an 8 pin round or RJ-45 modular
connector equipped microphone.
Endless-Loop Timer: Convenient front panel controls adjust repeat-message interval of 0.5-50
seconds or 5-500 seconds. Timing cycle begins at the end of your message.
Built-in Mic Interface: Internal jumpers for connection to transceivers including Yaesu, Icom,
and Kenwood/Alinco radios.
Automatic Message Stop: Microphone PTT switch automatically halts outgoing messages.
Manual Message Stop: Prominent red STOP button halts outgoing messages.
Built-in Amplifier/Speaker: Monitors outgoing messages and previews stored messages.
Two Microphone Sources: Record from your station microphone for seamless audio
continuity, or use the built-in electret microphone.
External Microphone Power Select: Adjust internal jumpers to select the proper microphone
power level appropriate for your external microphone.
Off-Air Recording: Capture signals from your receiver's audio jack for review or replay.
RFI Proof Circuitry: Extensive suppression and line isolation virtually eliminates RF feedback,
hum, and distortion. Isolation transformer prevents mic circuit ground loops.
Dual-Level Gain: Spreads adjustment range for more precise mic gain settings.
Transparent Audio: Keyer electronics won't color your station's normal audio quality.
User-Friendly Panel: Intuitive controls for easy operation under pressure.
External Control: Fully buffered TTL or CMOS level control lines available at rear panel for
external PC or remote control interface. Works with popular logging programs like CT or NA.
Power Flexibility: Power from external filtered 9-15 Vdc external source, or power temporarily
with internal 9V battery.
Rugged Construction: Tough all aluminum cabinet and surface mount construction means DX-
pedition survivability, RF immunity, and years of reliable operation.

MFJ MFJ-434B Specifications

General

Type	Digital Voice Recorder
Recording Format	Digital
Dimensions	6.5 x 2.5 x 1.5 inches
Weight	0.5 lbs
Memory	Built-in
Battery	9V Battery

Summary

Introduction to the MFJ-434B Voice Keyer

Key Features Overview

Highlights of the MFJ-434B's capabilities and design.

Operational Controls and Features

Details on mic interface, message stop, amp/speaker, mic sources, etc.

Connectivity and Construction

Information on external control, power, and rugged build.

Powering Your MFJ-434B

External Power Supply

Requirements for using an external 9-15 Vdc power source.

Internal Battery Power

Guidelines for using a 9-volt battery, noting short life.

Connecting and Operating the MFJ-434B

Front Panel Controls and Indicators

Description of the controls and LEDs on the front panel.

Rear Panel Connections

Power and Audio Ports

Details on power input, audio out, and audio in jacks.

Radio Interface Ports

Description of the "To Radio Mic" and "Ground" terminals.

Microphone Connections and Settings

External Microphone Voltage Selection

How to set internal jumper J6 for microphone voltage.

Microphone Jumper Configuration

Icom, Kenwood, Yaesu Settings

Factory jumper settings for common transceiver brands.

Custom Radio Settings

Steps to configure jumpers for other radio models using wiring diagrams.

Internal Adjustments and Audio Lines

Dual Gain Control (R29)

Trimpot to adjust Output Level Control range.

PTT Automatic Override (JMP1)

Jumper to enable PTT to stop messages.

Audio Input and Output Jacks

Details on the 3.5mm jacks for audio recording and monitoring.

Remote Port and Initial Setup

Remote Port Functionality

Access to memory lines and transmit signal via 8-pin IDC connector.

Initial Setup Steps

Pre-setting controls before powering up the unit.

Recording Messages

Choosing Audio Source

Selecting internal mic, station mic, or audio in for recording.

Message Memory Management

Memory Slot Capacity

Details on the duration limits for each of the 5 message slots.

Message Playback Operations

Previewing and Transmitting Messages

How to listen to and send recorded messages.

Loop Playback and Halting

Continuous playback modes and methods to stop playback.

Output Level Adjustment and Self Test

Setting Transmit Audio Level

Adjusting output level to match station microphone.

Performing Unit Self Test

Sequence to check unit's functions and indicators.

External Control and Remote Switches

External Control Circuits

Interface for remote control switches or PC.

Simple Manual Remote Switch

Components for building a manual remote control box.

Computer Interface Details

PC Interface Circuit Design

Recommended circuit for reliable computer control.

Parts List and Troubleshooting

Component Parts List

List of resistors, capacitors, and transistors used in the unit.

Troubleshooting Common Issues

Solutions for power, PTT, mic, and audio playback problems.

Technical Assistance and Further Troubleshooting

Specific Audio Recording Issues

Addressing distorted or weak recordings from the Audio In jack.

Contacting Support Channels

Information for MFJ Technical Service via phone, mail, or email.

Circuit Schematic Diagrams

Main Control Schematic

Diagram showing the PIC microcontroller and primary components.

Component Values and Labels

Details on resistance, capacitance, and component designations.