MFJ-9420 Installation Manual
20-Meter SSB Travel Radio
SETTING UP YOUR MFJ-9420 PORTABLE STATION
To put your MFJ-9420 station in operation, you will need a power source, a 20-Meter antenna,
and a microphone. Here are some specific suggestions to help you get started:
POWER SOURCE: 12 15 V @ 2A (+) TO CENTER PIN
The MFJ-4114 AC/DC PORTABLE POWER PACK and MFJ-4110 AC wall adapter supply are
especially designed for your radio. However, you may use any filtered DC power source capable
of delivering 12 15 volts at 2 Amps (13.8V required for full RF output). The DC power
connector at the rear of your MFJ-9420 is a 5.5mm OD, 2.1mm ID coaxial type jack. Extra
plugs are available from RadioShack stores (#274-1567). Always connect plus (+) to the
CENTER PIN.
MICROPHONE: USE 600 OHM DYNAMIC
The MFJ-9420 speech circuit is designed especially for 600 Ohm dynamic microphones such as
the MFJ-290 (the MFJ-290 is supplied if you purchase the MFJ-9420M package). You may also
use other suitable 600 Ohm desk or hand mics by installing a 5 pin DIN plug (Radio Shack
#274-003). See installation diagram below:
PTT pin 3
MIC pin 4
GND pins 1,2,5.
1
4
2
5
3
WARNING:
NEVER USE AN AMPLIFIED MICROPHONE WITH YOUR TRANSCEIVER.
The speech processor already has extremely high gain and may distort severely
overdriven by a "power mic".
ANTENNA REQUIREMENTS: VSWR 3:1 OR LESS
The MFJ-9420 accepts most 20-Meter antennas with a VSWR of 3:1 or less. Use your regular
station antenna or a portable 20-Meter dipole such as the MFJ-1772 ultra light. For non-resonant
wires, use a tuner such as the MFJ-971. Always "rough tune" for maximum receiver sensitivity
first using incoming signals and your S-Meter to find a peak. AVOID OPERATING INTO
UNMATCHED HIGH VSWR ANTENNAS. THE MFJ-9420 DOES NOT HAVE A HIGH
VSWR SHUT DOWN CIRCUIT AND BADLY MISMATCHED LOADS COULD RESULT IN
TRANSMITTER INSTABILITY AND GENERATION OF OUT OF BAND SIGNALS!
