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MFJ MFJ-976, Instruction Manual

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MFJ MFJ-976 Instruction Manual Download Page 13

MFJ-976 Legal Limit Fully Balanced Antenna Tuner 

Instruction Manual 

13 

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 

   

 

 

 

 

 

 

 

 

Summary of Contents for MFJ-976

Page 1: ...tructions Before Operating Equipment MFJ ENTERPRISES INC 300 Industrial Park Road Starkville MS 39759 USA Tel 662 323 5869 Fax 662 323 6551 COPYRIGHT 2006 MFJ ENTERPRISES INC C Model MFJ 976 VERSION 1B 1500 Watt Fully Balanced Antenna Tuner ...

Page 2: ...bile whips yagi beams quad loops horizontal loops sterba curtain arrays random wires and many other antennas The MFJ 976 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...

Page 3: ...e 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 value Reflected power is ...

Page 4: ...mpers on the right side of the rear panel Figure 2 shows the location of these jumpers with dashed lines The jumpers may remain connected to the ground terminal but make certain they cannot make contact with one of the connection terminals on the fiberglass plate See Figure 2 ii Connect your balanced feedline to the balanced line terminals located on the left side of the rear panel See Figure 2 No...

Page 5: ... roller Therefore as you turn the roller up and down you may feel a bump This is normal and you should not be alarmed Increase the number the controls are set at on a given frequency to INCREASE the matching range Remember this LOWERS the efficiency and power handling capability of the tuner 1 Tune the exciter into a dummy load most solid state transmitters are pre tuned to 50 ohms and do not requ...

Page 6: ... controls are set at the lowest possible number and the INDUCTOR control is set at the highest possible letter that permits matching the antenna Following this guideline will ensure maximum power handling capability and efficiency and the smoothest tuning Operating Notes While this tuner is designed to have as large a tuning range as possible there are limits to the tuning range of the capacitors ...

Page 7: ...icularly important to have a good RF ground when using a single wire feeder When using a single wire feeder the tuner needs something to push against in order to force current into the single wire feed line If a good RF ground is not available RF will usually find its way back into the power line RFI transmitter audio circuits RF feedback or the operator RF burns Water pipes and ground rods provid...

Page 8: ...e 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 The half wave line repeats the high antenna impedance at the tuner The antenna system looks like several thousand ohms at the tuner on 40 meters This places ...

Page 9: ...erence meter Adjust the LO FWD trim pot to set the forward power scale to 100 Watts 5 With the 3000 300 Watts button pushed in for the 3000 Watt scale Transmit 1000 Watts as indicated on the reference meter Adjust the HI FWD trim pot to set the forward power scale to 1000 Watts 6 To set the reflected power interchange the TRANSMITTER and ANTENNA coax cables so that the transmitter is connected to ...

Page 10: ...ale Transmit 100 Watts as indicated on the reference meter Adjust the HI REF trim pot to set the reflected power scale to 100 Watts 9 SWR requires no calibration Figure 1 Test Setup Figure 2 PCB Layout and Trim Pot Location Transmitter Transceiver Standard Reference Wattmeter MFJ 976 SWR Wattmeter 50 Ohm Dummy Load HI FWD LO REF HI REF LO FWD ...

Page 11: ...e MFJ Factory at 662 323 5869 You will be best helped if you have your unit manual and all information on your station handy so you can answer any questions the technicians may ask You can also send questions by mail to MFJ Enterprises INC 300 Industrial Park Road Starkville MS 39759 by Facsimile FAX to 662 323 6551 or by email to techinfo mfjenterprises com Send a complete description of your pro...

Page 12: ... 79 1 5 800 3 75 0 97 1 25 3 75 1 97 0 50 3 75 0 80 2 800 4 0 1 100 0 25 4 0 2 99 0 25 4 0 0 84 2 50 5 34 2 105 0 800 7 15 2 112 0 25 7 15 3 110 0 50 7 15 0 97 6 800 10 1 4 5 116 0 25 10 1 4 5 114 0 50 10 1 8 103 7 800 14 2 6 5 117 0 25 14 2 6 114 0 50 14 2 7 113 0 800 18 1 7 5 117 0 25 18 1 7 109 0 50 18 1 9 111 0 800 21 2 8 114 0 25 21 2 8 116 6 50 21 2 0 114 9 800 24 9 8 5 119 6 25 24 9 8 117 7...

Page 13: ...tenna Tuner Instruction Manual 13 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 ...

Page 14: ...MFJ 976 Legal Limit Fully Balanced Antenna Tuner Instruction Manual 14 Schematic ...

Page 15: ...rovided to cover postage and handling 4 This warranty is NOT void for owners who attempt to repair defective units Technical consultation is available by calling 662 323 5869 5 This warranty does not apply to kits sold by or manufactured by MFJ Enterprises Inc 6 Wired and tested PC board products are covered by this warranty provided only the wired and tested PC board product is returned Wired and...

Page 16: ...MFJ 976 Manual Version 1C Printed In U S A 300 Industrial Park Road Starkville MS 39759 ...

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