MFJ-9420 Installation Manual
20-Meter SSB Travel Radio
QUICK START INSTRUCTIONS:
You will need three things to get your MFJ-9420 on the air fast:
[ ] 12 14 Volt 2 Amp Power Source
[ ] 600 Ohm Dynamic PTT Microphone
[ ] 20-Meter Antenna
1. POWER SUPPLY: The MFJ-4114 AC/NiCd Portable Power Pack or MFJ-4110 AC wall-
adapter supply are Especially designed to run the MFJ-9420. You may also use any 13.8 Volt
supply or 10-cell NiCd pack as long as it delivers 2 A on peaks (12 Volt supplies will work fine
but at reduced RF output). Use a 5.5mm OD x 2.1mm coaxial type power plug (Radio Shack
274-1567) with (+) connected to the center pin.
2.
MICROPHONE: The MFJ-9420 speech processor circuit was designed around the
companion MFJ-290 600 Ohm Dynamic Microphone. Radio Shack's 21 1172 replacement
microphone also plugs in without modification and works well. If the mic you select requires a
plug, install a 5 Pin DIN connector (Radio Shack 274 003) as shown:
Pin 3: PTT Line
Pin 4: Mic Line
Pin 1,2,5: Ground
3. ANTENNA: The MFJ-9420 will function with any 20-Meter antenna exhibiting a VSWR of
3:1 or less (your home station antenna or the MFJ-1772 Portable Dipole should work fine).
AVOID USING ANTENNAS WITH UNKNOWN OR HIGH VSWR. The MFJ-9420 PA is not
protected by high VSWR shutdown circuitry and you may generate out-of-band parasitics if a
high VSWR load is present.
IMPORTANT OPERATING NOTES
Your MFJ-9420 features a very potent speech processor. PLEASE RESIST THE
TEMPTATION TO SHOUT OR "CLOSE TALK" INTO THE MICROPHONE IN ORDER TO
BE HEARD! Instead, hold the mic about 2"away and speak normally. The S-Meter should
deflect about 1/2 scale as you speak although this may vary somewhat with antenna load. When
operating in noisy environments, you may find it necessary to turn down the mic gain control (a
screwdriver adjustment located on back panel) to reduce background noise.
The MFJ-9420 uses an analog VFO tuning dial that is inherently less accurate than digital
readouts (on the plus side, analog tuning reduces phase noise, lowers power consumption, and
saves you money). Please take the potential for dial error into account when operating near the
edge of your authorized sub band.
