If you suspect condensation, allow radio to fully dry out.
7. POOR CARRIER SUPPRESSION
Was radio moved from extreme cold to warm (condensation)?
Was radio exposed to rough handling or shock?
To null, unplug mic and ground pin 3 to key radio. Adjust R36
and T3 for minimum carrier (monitor using a second receiver).
8. LOW TRANSMIT AUDIO:
Is the mic a 600 ohm dynamic type?
Is the MIC GAIN set too low?
9. NOISE ON TRANSMIT AUDIO:
Is MIC GAIN set too high in a noisy room?
Is mic next to a power transformer or motor?
If these checks don't uncover the problem, or if you don't 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 Receiver with digital readout
INITIAL TEST SET UP:
A. Remove transceiver cover.
B. Connect 13.8 Volts Power Supply to Power Jack.
C. Connect Microphone.
D. Turn on unit.
VOLTAGE CHECKS AND ADJUSTMENTS: (use voltmeter)
A. VOLTAGE REGULATOR: Set R64 for 10.0 V at TP1.
B. RECEIVER AGC: Set R6 for 4.3 Volts at TP2.
VFO CALIBRATION:
A. Tune VFO dial to 14.250 MHz (mid band).
B. Connect counter probe to U7 pin 6
C. Adjust L3 for 4.255 MHz readout.
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 VFO dial to lower frequency response peak.
D. Adjust BFO trimcap (C61) until CW note is 600 Hz.
E. Recheck. First peak should be at 600 Hz, second peak around 2000 Hz. Pitch of CW tones should go
DOWN as you tune UP in frequency, indicating USB operation.
CARRIER NULL: (use a second receiver to monitor beat note)
A. Short mic pin 4 to ground to kill mic pickup.
B. Key mic and monitor signal slightly off frequency.
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