MFJ MFJ-989D, Instruction Manual

Page 1: ...AUTION Read All Instructions Before Operating Equipment COPYRIGHT 2014 MFJ ENTERPRISES INC C Model MFJ 989D VERSION 2A MFJ ENTERPRISES INC 300 Industrial Park Road Starkville MS 39759 USA Tel 662 323 5869 Fax 662 323 6551 ...

Page 2: ... manuals documents positional handbooks or other official publications The copy of this manual provided to the customer will not be updated to reflect current data Customers using this manual should report errors or omissions recommendations for improvements or other comments to MFJ Enterprises 300 Industrial Park Road Starkville MS 39759 Phone 662 323 5869 FAX 662 323 6551 Business hours M F 8 4 ...

Page 3: ...on cross needle movements with LED illumination a compensated directional coupler and dual detectors for measuring average and instantaneous peak power Circuit is identical to our MFJ 815C TrueActive TM stand alone meter 2 Antenna Selector Switch Heavy duty ceramic switch with silver plated contacts and six positions for routing a variety of loads to your transmitter or amplifier 3 Dummy Load Prec...

Page 4: ...rner of the front panel We strongly recommend installing a battery even if you intend to use an external power source Doing so provides backup voltage to operate the meter and also prevents the battery snap clip from floating loose inside the cabinet where it could contact high RF potentials If you elect to omit the battery make sure the snap clip is anchored solidly to the battery holder where it...

Page 5: ... 6 7 8 9 MFJ VersaTuner V MFJ 989D PK 0 10 0 10 1 Transmitter Tuning Capacitor Series capacitor on the Transmitter side of the T network Maximum capacity at 0 knob setting and minimum capacity at 10 2 Antenna Tuning Capacitor Series capacitor on the Antenna side of the T network Maximum capacity at 0 and minimum capacity at 10 3 Rotary Inductor Continuously adjustable shunt Inductor with maximum i...

Page 6: ...alanced Line Operation 12V DC 5 4 3 7 1 Meter Lamp 2 1 mm coaxial power jack accepts 12 vdc to operate the LED meter lamps and the metering circuit see text 2 Transmitter Accepts PL 259 connects transceiver or amplifier to tuner 3 Coax 1 Accepts PL 259 connects antenna 1 to tuner routing switch 4 Coax 2 Accepts PL 259 connects antenna 2 to tuner routing switch 5 GND Chassis ground connects tuner t...

Page 7: ... the cable 3 Tuner Grounding Connect the tuner chassis directly to your station s ground system Don t rely on the patch cable to ground the tuner to your radio or amplifier 4 Lightning Protection Make provisions to disconnect all antennas from your station in the event of violent weather Lightning arrestors may reduce damage from nearby strikes but only disconnection can reduce the odds of damage ...

Page 8: ...s taken along the upper two thirds of the meter scale are typically more accurate than those made along the lower third 2 Measuring Power with SWR When measuring transmitter power into a mismatched load indicating reflected power remember to subtract the Reflected Power reading from the Forward Power reading Po FP RP 3 Precision SWR Readings To obtain precise SWR data using the split meters write ...

Page 9: ...d to check any radio running 300 Watts or less for true peak power power or average power output through the tuner s precision wattmeter The Dummy Load resistor is convection cooled through the bottom of the cabinet and is rated to safely dissipate 300 Watts of applied RF for up to 30 seconds at a time The minimum cool down period between power applications is specified at 2 minutes Longer tune up...

Page 10: ...pment The T configuration using two series capacitors and a shunt inductor belongs to the high pass filter family and as such it does little to suppress transmitter harmonics However modern transceivers and amplifiers must meet stringent harmonic suppression requirements on their own to satisfy FCC requirements so there s little need for high frequency suppression in the tuner 2 The C high L low R...

Page 11: ...na loads using the least amount of power needed to obtain a useful SWR reading 25 Watts or less 6 Antenna Analyzers As an alternative to using a transceiver you may also use an antenna analyzer to tune an unknown load Connect the analyzer to the tuner s Transmitter connector set if for the desired frequency and refer to its SWR display as you adjust the tuner s controls Using an analyzer eliminate...

Page 12: ... find the lowest front panel capacitor settings that will allow you to obtain minimum SWR The chart below shows sample control settings for a MFJ 989D recorded in our lab using 50 Ohm unbalanced and 600 Ohm balanced loads Your optimum settings will vary somewhat depending on the characteristics of your particular antenna Frequency MHz Transmitter Inductor Counter Antenna Load Ω 1 8 0 5 41 0 5 50 1...

Page 13: ...maximum output Follow the amplifier manufacturer s prescribed tuning procedure paying attention to grid or screen current Once you ve optimized tuner settings and peaked the amplifier for maximum output don t reset the tuner controls If arcing or component heating occur because of an extreme load condition reduce transmitter power and explore taking corrective action for your antenna system A Word...

Page 14: ...R may not be reduced to 1 1 Normally this isn t a problem but if the residual SWR is higher than the radio s SWR detection circuitry can handle typically 2 1 you may need to change the length of the antenna radiator or its feedline in order to bring the load impedance back within the tuner s range Extreme load conditions may also lead to arcing or component heating in the tuner so they should alwa...

Page 15: ...na counterpoise RF grounds work better when spread out over a large area with multiple connections to the equipment ground point A RF radial system or multi wire counterpoise is ideal because it provides a large low resistance mat to reinforce the antenna If installing a good RF ground isn t possible it s best to avoid using unbalanced monopole designs that depend on ground reinforcement Regardles...

Page 16: ...ally this antenna will be extremely reactive with only a few ohms of feed point resistance In other words it will be nearly impossible to match When feeding any dipole with high impedance line use the approximate lengths shown in the table below Note that the worst possible lengths are also shown 160 meter dipole 35 60 170 195 210 235 feet Avoid 130 260 ft 80 meter dipole 34 40 90 102 160 172 feet...

Page 17: ...he chart below to log tuner settings for your station You may want to copy this chart and post it by your tuner Frequency Transmitter Inductor Antenna 1 8 1 8 2 0 2 0 3 5 3 5 3 5 3 75 3 75 3 75 4 0 4 0 4 0 7 15 7 15 10 1 10 1 14 2 18 1 18 1 21 2 21 2 24 9 28 5 ...

Page 18: ...MFJ 989D VersaTuner V Instruction Manual 18 NOTES ...

Page 19: ... be provided 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 601 323 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 Wire...

Page 20: ...MFJ 989D Manual Version 2A Printed In U S A 300 Industrial Park Road Starkville MS 39759 ...