MFJ Enterprises MFJ-9420 Instruction Manual Download | Manualshive

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MFJ-9420 Installation Manual

20-Meter SSB Travel Radio

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Summary of Contents for MFJ-9420

Page 1: ...nufactured 8 1 reduction drive ball bearing VFO tuning capacitor provides smooth and stable VFO Fine Tune lets you zero in smoothly 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 1...

Page 2: ...d 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 ...

Page 3: ...r 12 dB S N Audio 1 Watt into 8 Ohms at 10 THD Receive Current 50 100 mA typical TRANSMITTER SECTION RF Power Output 10W Average Speech 8 10W CW VSWR Tolerance 3 1 VSWR Maximum Current 2 2 Amps peak at 13 8 VDC Audio Enhancement RF compression processor Requires CW adapter module BLOCK DIAGRAM RX BPF L1 L2 VFO RX MXR U1 BFO PROD DET U3 SW Q5 AF AMP U4a AF PWR U5 XTAL FILTER IF AMP U2 AGC Q2 Q4 SW ...

Page 4: ...kills U4 output to prevent mic bleed through via U6 U2 during RX LO for U6 is derived from U3 s 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 and carrier artifacts After undergoing dynamic compression in U2 the processed USB signal is routed to transmitter mixer U7 by switch D3 D4 where it i...

Page 5: ...epts straight key or keyer XMIT POWER MIC TUNE ON ON OFF OFF 150 000 050 100 150 200 250 300 350 VOLUME MFJ 20 METER SSB TRANSCEIVER MODEL MFJ 9420 TUNING SSB CW CW SSB MHz 14 000 1 3 5 7 9 PROCESS 0 S 7 10 30dB 10 400 4020 6 8 7 2 3 5 1 4 FINE TUNE FRONT PANEL 1 METER Show signal strength on RX ALC on TX 2 POWER SWITCH Turns power on to transceiver 3 MIC 5 Pin Din Jack for Dynamic Microphone 4 TU...

Page 6: ...c 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 an...

Page 7: ...ocation of band edges b Avoid transmitting on the margins of your allocation unless you are certain the station you are calling is in in band STEP 6 To transmit press the mic s PTT switch and speak at normal conversational level with the mic held about 2 inches from your mouth The MFJ 9420 has a very potent speech processor and will pick up your voice at full intensity Avoid the natural temptation...

Page 8: ... fed dipole consider purchasing the pre assembled MFJ 1772 antenna This is a no compromise 20 Meter folded dipole complete with 30 of feedline all made from ultra lightweight 300 Ohm twinlead Connect a random length of coax from the MFJ 1772 feedline to your rig and let the antenna s built in 50 Ohm matching network do the rest The antenna is pre tuned easy to handle and sufficiently broad banded ...

Page 9: ...d QSOs a practice called tailgating Never hesitate to call a weak station because it may be QRP or using a marginal antenna You may be much louder than you think Be realistic about diving into huge 20 Meter pileups Once a choice DX station hits the packet clusters and the big guns move in calling may be a waste of time until the smoke clears Tune slowly and listen carefully If one exotic station i...

Page 10: ...ion 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 prob...

Page 11: ...nately adjust R36 and T3 for minimum carrier RECEIVER SENSITIVITY CHECK A Connect weak 14 250 MHz signal source to antenna jack B Tune in signal source for maximum S Meter reading C Touch up L1 L2 T1 and T2 for max SIG Meter reading TRANSMITTER BANDPASS FILTER AND COMPRESSOR ALIGNMENT A Connect QRP Wattmeter with dummy load to ANT Jack B Turn R61 fully CW and then the Press Carrier Switch SW2 C Ca...

Page 12: ...Source Base G C Gate Collector Test in TRANSMIT mode 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 full ...

Page 13: ...MFJ 9420 Installation Manual 20 Meter SSB Travel Radio SCHEMATIC ...

Page 14: ...MFJ 9420 Installation Manual 20 Meter SSB Travel Radio ...

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