MFJ-434B Instruction Manual Voice Keyer
1
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.
