MFJ Enterprises 9420 Hf Tranceiver Manual
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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 The MFJ-9420 is an easy-to-operate,back to basics radio. Operate the unit with ease in minutes! Quiet DBM front end and lots of overall gain for great sensitivity. If the signal is there, youll hear it! Adjust the tuner or...
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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...
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amplifier U5 through the volume control. U5, which powers the speaker during RX, is gated into standby during TX to prevent residual feed through. TRANSMITTER: Microphone speech amp U4b drives balance modulator U6 during TX (switch Q6 kills U4 output to prevent mic bleed through via U6/U2 during RX). LO for U6 is derived from U3s BFO oscillator. Q8 is used to unbalance U6 for carrier or CW generation. DSB output from U6 is routed to Y1 Y6 via switch D1/D2 for removal of LSB products...
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MICROPHONE: USE 600 OHM DYNAMIC The MFJ 9420 speech circuit is designed especially for a 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. WARNING: NEVER USE AN AMPLIFIED MICROPHONE WITH YOUR TRANSCEIVER. The speech...
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your voice at full intensity. Avoid the natural temptation to yell or close talk this will only overload the processing circuit and hurt the intelligibility of your signal! SPECIAL OPERATING NOTES: The MFJ 9420 does not have automatic high VSWR shutdown and you must provide a reasonable 20 Meter antenna to ensure proper operation. 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...
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Tune slowly and listen carefully. If one exotic station is coming through, there may be others you can work nearby. Pay attention to DX forecasts and gray line propagation. When the band is hot, power differences become much less significant. Operating just before the band goes out at night may yield strong signal reports from exotic locations with little QRM. Dont be shy about calling. The MFJ 9420 has very potent audio and on air tests indicate its signal is competitive with higher...
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If these checks dont uncover the problem, or if you dont feel qualified to make the prescribed adjustments, please call us for help at 800 647 TECH (800 647 8324). FIELD ALIGMENT PROCEDURES FOR THE MFJ 9420 TRANSCEIVER: SPECIAL TOOLS, PARTS, TEST EQUIPMENT: AC Power Supply, 13.8 Volts @ 2 Amps Voltmeter Non inductive Alignment Tool kit Frequency Counter Wattmeter with 50 Ohm Resistive Dummy Load 14 MHZ Signal Generator or other weak signal source General Coverage...
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AGC: U2 AGC threshold M ZERO: Panel meter zero BFO: Carrier osc. freq. VFO CAL: VFO freq. adj. IF1,IF2: IF ampl. peak L1,L2: RX front end peak L5,L6: TX filter peak CAR BAL,T3: Carrier null PA BIAS: PA idle current SP PROC: TX ALC level MIC GAIN: TX audio level TUNE SW: Full carrier out PWR: Power on VOL: AF Ampl. gain control VFO TUNE: Sets operating freq. FUSE: Reverse polarity protect *If reverse polarity track fuse opens, install a miniature 2.5 A pigtail fuse or a 3/4 hair pin...
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** = Test with TUNE switch depressed
*** = DO NOT TEST gate of Q9 may cause generation of parasitic oscillations.
Q1 Q2 Q3 Q4 Q5* Q6 Q7* Q8** Q9 Q10
D/E 9.8 0 9.0 9.7 0 0 3.5 0 13.0 0.25
S/B 2.3 0.7 3.9 8.9 0.7 0.7 2.8 0 0 1.0
G/C 0 13.2 0 4.3 13.0 0 0 9.0 *** 13.7
Q11 (MRF477 PA Transistor): To avoid RF damage to DVM, check collector voltage in receive mode only...