MFJ -9420X Installation Manual

MFJ -9420X Installation Manual

20-meter ssb travel radio

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MFJ-9420 Installation Manual
INTRODUCTION
Congratulations on your choice of the MFJ-9420 20-Meter transceiver. The MFJ-9420 is specially designed to
deliver performance you never thought possible from a low power radio. Please read this manual carefully before
attempting to operate your new radio.
FEATURES
EASY TO OPERATE: The MFJ-9420 is an easy-to-operate," back to basics" radio. Operate the unit with ease in
minutes!
GREAT SENSITIVITY: Quiet DBM front end and lots of overall gain for great sensitivity. If the signal is there,
you will hear it!
ANALOG S-METER: Adjust the tuner or aim the beam with pinpoint accuracy. A calibrated analog S-Meter
measures even the smallest variations in signal strength. The meter also monitors your speech processing level on
transmit.
EXCELLENT SELECTIVITY: Sharp ladder filter cuts adjacent chatter and focuses transmitter power where you
need it most for great selectivity.
SMOOTH, STABLE VFO: Effortless tuning with custom manufactured 8:1 reduction drive ball bearing VFO
tuning capacitor provides smooth and stable VFO.
POWERFUL AF OUTPUT: Big audio and powerful AF output even in noisy locations from a special Philips BTL
audio chip and rugged 3" speaker.
FULL-TIME RF SPEECH PROCESSING: Commanding speech cuts through QRM and competes with radios
running far more power. Compare with your 100-watt rig. You will be amazed by the signal reports!
TRAVEL LIGHT: Packs the same punch as 50-Watt radios without the heavy 10 Amp power supply! Designed to
run on NiCd's or the ultra light MFJ-4110 AC wall adapter supply.
RUGGED TRANSMITTER: Bullet-proof Motorola PA transmitter runs cool, and tolerates 3:1 VSWR accidentally
opened feedlines or feedline shorts.
MADE TO LAST: Conservative design, with a premium plate through pc board, quality components, handsome
brushed aluminum panel, and a tough vinyl clad case ensure years of dependable service.
CW ADAPTER AVAILABLE: Install the MFJ CW adapter board jump to the low end to work CW. Semi-break in
keying and sidetone.
At home or on the go, you will enjoy countless hours operating the MFJ-9420. Best of all, it is fully backed by
MFJ's exclusive "No Matter What" 1 year guarantee. If it breaks, we will take care of it!
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.
20-Meter SSB Travel Radio

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Summary of Contents for MFJ MFJ-9420X

  • Page 1 At home or on the go, you will enjoy countless hours operating the MFJ-9420. Best of all, it is fully backed by MFJ's exclusive "No Matter What" 1 year guarantee. If it breaks, we will take care of it!
  • Page 2: Important Operating Notes

    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.
  • Page 3: Theory Of Operation

    Level detector D9 tracks the SSB speech envelope and generates feedback to Q3/Q4 and U2. Syllabic compression of the speech waveform optimizes average transmitter output power. The MFJ-9420 is especially designed to operate from lightweight constant current power sources such as NiCd cells or the MFJ wall adapter AC supply.
  • Page 4 MFJ-9420 Installation Manual 20-Meter SSB Travel Radio MFJ-9420 CONTROL LOCATION AND FUNCTION MFJ ENTERPRISES, INC. ANTENNA STARKVILLE, MS USA INPUT POWER 12-15VDC GAIN 1.2 AMP REAR PANEL 1. POWER JACK: 5.5mm OD, 2.1mm ID, (+) to center pin. 2. ANTENNA JACK: SO 239 for standard coax plugs.
  • Page 5 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.
  • Page 6: Special Operating Notes

    Whenever possible, use a low SWR resonant type antenna such as a dipole or tuned vertical. If you use an ATU (or a high Q loop such as the MFJ-1786 or Isopole 10 30), carefully rough tune first for maximum S-Meter readings before activating the CARRIER switch.
  • Page 7: Troubleshooting

    QRM. Do not be shy about calling. The MFJ-9420 has very potent audio and on air tests indicate its signal is competitive with higher-powered radios. If your antenna is good, most stations will not even know you are running low power! TROUBLESHOOTING IN CASE OF TROUBLE, CHECK IT OUT FIRST –...
  • Page 8 If these checks don't uncover the problem, or if you do not feel qualified to make the prescribed adjustments, please call us for help at 800-647-TECH (800-647-8324). FIELD ALIGNMENT PROCEDURES FOR THE MFJ-9420 TRANSCEIVER SPECIAL TOOLS, PARTS, TEST EQUIPMENT: AC Power Supply, 13.8 Volts @ 2 Amps...
  • Page 9: Internal Adjustment Locations

    MFJ-9420 Installation Manual 20-Meter SSB Travel Radio BFO FREQUENCY CHECK AND ALIGNMENT: A. Tune across 14.250 MHz. test signal (use generator). B. Identify 2 peaks in passband by watching S-Meter. C. Carefully set the VFO dial to lower frequency response peak.
  • Page 10 DC VOLTAGE CHART TROUBLESHOOTING GUIDE For advanced troubleshooters, the following are typical DC voltages found in the MFJ-9420. Voltages were checked with handheld probe type DVM to minimize effects of lead inductance and to limit the potential for RF feedback.
  • Page 11 MFJ-9420 Installation Manual 20-Meter SSB Travel Radio SCHEMATIC...
  • Page 12: Parts List

    MFJ-9420 Installation Manual 20-Meter SSB Travel Radio PARTS LIST DESIGNATION DESCRIPTION PART # DESIGNATION DESCRIPTION PART # C1,5,73 100pF, 50V Multilayer 205-0100 VN10KM 305-6005 560pF, 50V Multilayer 205-0005 J310 305-6310 C3,7,11,18,19,20,21,27 .01uF, 25/50V Disc 200-0004 2N5109 305-0017 C28,29,34,36,38,42,45,52 .01uF, 25/50V Disc...

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