MFJ MFJ-974 Instruction Manual Download | Manualshive

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MFJ-974/974H Balanced Line Antenna Tuner

Instruction Manual

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Summary of Contents for MFJ-974

Page 1: ... arrays random wires and many other antennas The MFJ 974H has rear panel connectors for coaxial and single or two wire feedlines The built in balun works with balanced open wire twinlead or twin axial feedlines Understanding Power Ratings There are no standardized power rating systems for tuners The names used i e 3 kW Tuner carry over from the time when amplifiers were rated by peak power input a...

Page 2: ...the true peak envelope power Forward power is displayed on the left hand FORWARD meter scale This scale is calibrated from 0 to 300 watts In the HI position each picket scale mark represents 5 watts below 10 watts 10 watts between 10 and 100 watts and 25 watts between 100 and 300 watts In the LO power position full scale meter reading is 30 watts divide the meter reading by 10 for the correct valu...

Page 3: ...al line is connected to the BALANCED LINE terminals 4 A ground post is provided for an RF ground connection Operation The MFJ 974H uses three inductors for maximum efficiency A 2 inch diameter high Q air wound inductor is tapped for flexibility and is used on frequencies from 3 5 to 30 MHz For 160 Meters MFJ 974H only an additional inductance made of Teflon insulated wire wound on two powdered iro...

Page 4: ...t and touch up the tuner settings if needed 8 For quick retuning of the tuner record the INDUCTOR and CAPACITOR settings for each band see the Logged Tuning Chart Page 10 Note Maximum power handling is achieved when both the ANTENNA and TRANSMITTER controls are set at the lowest possible number and the INDUCTOR control is set at the highest possible letter that permits matching the antenna Followi...

Page 5: ... single wire feeder runs parallel and reasonably close to the wire that connects the tuner to the outdoor ground The antenna feed wire should be adequately insulated to prevent arcing or accidental contact For safety please use good DC and RF grounds It is particularly important to have a good RF ground when using a single wire feeder When using a single wire feeder the tuner needs something to pu...

Page 6: ...e dipole s low impedance to over three thousand ohms at the tuner This is because the mismatched feedline is an odd multiple of 1 4 wavelength long The line inverts or teeter totters the antenna impedance A problem also occurs on 40 meters with this same antenna example The feedline is now a multiple of a half wave 60 to 70 foot and connects to a full wave high impedance antenna 100 to 140 feet Th...

Page 7: ... Starkville MS 39759 by Facsimile FAX to 662 323 6551 or by email to techinfo mfjenterprises com Send a complete description of your problem an explanation of exactly how you are using your unit and a complete description of your station WARNING To avoid problems a dipole antenna should be a full half wavelength on the lowest band On 160 Meters an 80 or 40 Meter antenna fed the normal way will be ...

Page 8: ...MFJ 974 974H Balanced Line Antenna Tuner Instruction Manual 8 ...

Page 9: ... 1 5 E 3 25 3 75 2 E 2 50 3 75 2 E 1 5 600 4 0 0 F 0 25 4 0 1 F 0 50 4 0 1 F 1 600 7 15 0 I 2 5 25 7 15 1 I 0 50 7 15 1 5 I 1 5 600 10 1 0 K 2 5 25 10 1 1 K 0 50 10 1 0 K 1 600 14 2 3 L 4 25 14 2 4 L 3 50 14 2 4 L 3 600 18 1 6 5 L 7 5 25 18 1 6 L 6 50 18 1 7 L 7 600 21 2 7 5 L 7 5 25 21 2 7 5 L 7 5 50 21 2 7 L 7 5 600 24 9 8 5 L 8 5 25 24 9 8 5 L 8 5 50 24 9 9 K 8 600 28 5 8 5 L 9 25 28 5 9 L 9 50...

Page 10: ...a Tuner Instruction Manual 10 Logged Tuning Chart Use the chart below to log values for your station You may want to copy this chart and post it by your tuner Frequency MHz ANTENNA INDUCTOR TRANSMITTER 1 8 3 5 7 10 1 14 18 21 24 28 50 ...

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