MFJ 904 Instruction Manual

MFJ-904/904H Deluxe Travel Tuner

INTRODUCTION

The MFJ-904/904H Travel Antenna Tuner was specially compact-built with
great features. The MFJ-904 has a Cross-Needle SWR/Wattmeter, 50 ohm SO-
239 connectors and a tuner/bypass switch. The MFJ-904H adds a binding post
for random wire and binding post with a 4:1 balun for balanced lines.
You can operate 80 through 10 Meters -- anywhere with any transceiver -- use
any coax fed, random wire or balanced line antenna. It's great for mobile, base,
backpack, etc. The MFJ-904/904H handles 150 watts RF output.

INSTALLATION

The MFJ-904/904H should be installed between the transmitter and antenna.
1. Locate the tuner in a convenient location at the operating position.
2. Use a 50 ohm coaxial cable to connect the transmitter or transceiver to the
SO-239 labeled TRANSMITTER on the back of the tuner.
3. Connect an antenna feed to the appropriate tuner output:
a.) COAX-FEED to the SO-239 connector labeled ANTENNA.
b.) RANDOM WIRE
MFJ-904: A random wire may be used by connecting to the center of
the SO-239 connector with the supplied plug.
MFJ-904H: Connect to the red binding post labeled WIRE.
The MFJ-904/904H must be grounded when using a random wire.
c.) BALANCED FEEDERS (MFJ-904H only) to the red binding posts
labeled BALANCED LINE. When using a balanced feedline, connect a
short jumper from the WIRE binding post to the closest balanced line
post (see labeling on back of unit).
4. Connect your tuner and transmitter to a good earth ground.

OPERATION

This tuner has a BYPASS/TUNE switch located on the back of the unit. Simply
place the switch toward the BYPASS labeling to completely bypass the tuning
circuit. Change the switch toward the TUNE labeling to place the tuning circuit
between the transmitter/transceiver and the antenna.
In this tuner the TRANSMITTER and ANTENNA matching controls have
maximum capacitance at position 0 (fully meshed), and minimum capacitance at
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Instruction Manual