MFJ-986 3KW Roller Tuner, SWR Meter, 1.8-30 MHz User Manual

1. Introduction

This manual provides comprehensive instructions for the setup, operation, and maintenance of the MFJ-986 3KW Roller Tuner. The MFJ-986 is designed to match a wide range of impedances to your transceiver, ensuring efficient power transfer and minimizing Standing Wave Ratio (SWR) across the 1.8 to 30 MHz frequency spectrum.

2. Safety Information

• Always disconnect power from your transceiver and antenna system before making any connections or adjustments to the tuner.
• Never operate the tuner with damaged cables or connectors.
• Ensure proper grounding of your station equipment, including the tuner, to prevent electrical shock and minimize RF interference.
• Do not exceed the maximum power rating of 3KW PEP SSB input (1500 Watts PEP SSB output) to prevent damage to the tuner or connected equipment.
• Avoid touching antenna connections during transmission. High RF voltages can be present.

3. Product Overview

The MFJ-986 is a robust Differential-T Tuner featuring a unique differential capacitor design for simplified tuning. It incorporates an AirCore Roller Inductor for precise inductance control and a lighted Cross-Needle meter for simultaneous SWR, forward, and reflected power readings.

Figure 1: MFJ-986 Front Panel Layout
This image displays the front panel of the MFJ-986 tuner. Key components include the SWR/Wattmeter on the left, the Differential Capacitance tuning knob in the center-left, the Antenna selector switch in the center, and the Inductance roller with its 3-digit counter on the right. Below the meter are switches for Range (HI/LO), Power (PK/AVG), and Lamp (ON/OFF).

Front Panel Controls:

• SWR/Wattmeter: Displays forward power, reflected power, and SWR simultaneously.
• Differential Capacitance Knob: Adjusts the capacitance for tuning. Marked 0-10.
• Antenna Selector Switch: Selects between various antenna connections: COAX 1, COAX 2, EXT. DUMMY LOAD, BAL. LINE, COAX 2 DIRECT, COAX 1 DIRECT.
• Inductance Roller with Counter: Provides precise control over the roller inductor, indicated by a 3-digit turns counter.
• Range Switch (HI/LO): Selects the power range for the meter.
• Power Switch (PK/AVG): Selects between peak or average power readings.
• Lamp Switch (ON/OFF): Controls the illumination of the meter.

4. Setup

1. Power Connection: The metering circuitry requires 12VDC. Connect a 12VDC power supply (such as the MFJ-1312D) or an MFJ-5513 cable to the 12VDC input jack on the rear panel.
2. Transceiver Connection: Connect the output of your transceiver to the "TRANSMITTER" SO-239 connector on the rear panel using a high-quality 50-ohm coaxial cable.
3. Antenna Connection:
   • Coaxial Antennas: Connect your coaxial antenna(s) to the "COAX 1" or "COAX 2" SO-239 connectors on the rear panel.
   • Balanced Line Antennas: Connect your balanced line antenna to the binding posts labeled "BALANCED LINE" on the rear panel.
   • Single Wire Antennas: Connect a single wire antenna to the "WIRE" binding post on the rear panel.
4. Ground Connection: Connect a good RF ground to the "GROUND" binding post on the rear panel. A proper ground is crucial for safe and effective operation.

5. Operating Instructions

5.1 Initial Power-Up and Metering

1. Ensure all connections are secure.
2. Turn on the 12VDC power supply for the meter.
3. Set the Lamp switch to ON if illumination is desired.
4. Select the appropriate Range (HI for high power, LO for low power) and Power (PK for peak, AVG for average) settings for your operating conditions.

5.2 Tuning Procedure

The MFJ-986 is designed for easy tuning, often requiring only one setting for minimum SWR due to its differential capacitor.

1. Select Antenna: Set the Antenna Selector Switch to the desired antenna port (e.g., COAX 1, BAL. LINE). If using a direct connection without tuning, select COAX 1 DIRECT or COAX 2 DIRECT.
2. Initial Settings:
   • Set the Differential Capacitance knob to a mid-range position (e.g., 5).
   • Set the Inductance Roller to a mid-range value (e.g., 150 on the counter).
3. Apply Low Power: With your transceiver set to a low power output (e.g., 5-10 watts), transmit a continuous carrier (e.g., in CW mode).
4. Adjust Inductance: Slowly rotate the Inductance Roller while observing the SWR meter. Find the point where the SWR reading is lowest.
5. Adjust Capacitance: Slowly rotate the Differential Capacitance knob while observing the SWR meter. Adjust for the absolute minimum SWR.
6. Fine-Tune: Make small, alternating adjustments to both the Inductance Roller and Differential Capacitance knob until the lowest possible SWR is achieved. The goal is to reach 1:1 SWR if possible.
7. Increase Power: Once minimum SWR is achieved at low power, you can increase your transceiver's power output to your desired operating level. Re-check SWR and make minor adjustments if necessary.

Note: The 3-digit turns counter on the Inductance Roller allows for precise recall of settings for specific frequencies and antennas. Record these settings for quick retuning.

6. Maintenance

• Cleaning: Keep the tuner clean and free of dust. Use a soft, dry cloth for cleaning the exterior. Do not use abrasive cleaners or solvents.
• Connections: Periodically check all coaxial and binding post connections to ensure they are tight and free from corrosion.
• Internal Inspection: If you suspect an internal issue (e.g., loose components as noted in some user feedback), it is recommended to have the unit inspected by a qualified technician. Opening the unit may void any warranty.
• Storage: Store the tuner in a dry, temperature-controlled environment when not in use.

7. Troubleshooting

• No Meter Illumination:
  • Ensure 12VDC power is connected and switched on.
  • Check the Lamp switch is in the ON position.
  • Verify the 12VDC power supply is functioning correctly.
• High SWR Readings / Difficulty Tuning:
  • Check all antenna and transceiver connections for proper seating and continuity.
  • Ensure your antenna is suitable for the operating frequency.
  • Verify the Antenna Selector Switch is set to the correct position for your connected antenna.
  • Confirm a good RF ground connection.
  • Ensure the Range switch is set appropriately for your power level.
  • Perform the tuning procedure carefully, making small adjustments to both Inductance and Capacitance.
  • Inspect the internal components for any loose wires or connections (if comfortable and knowledgeable, otherwise seek professional service).
• No Power Reading on Meter:
  • Ensure the transceiver is transmitting power.
  • Check the coaxial cable between the transceiver and tuner.
  • Verify the 12VDC power supply for the meter is connected and active.
  • Confirm the Range switch is set correctly.

8. Specifications

• Model: MFJ-986
• Tuner Type: Differential-T, Roller Inductor
• Power Rating: 3KW PEP SSB amplifier input power (1500 Watts PEP SSB output power)
• Frequency Coverage: 1.8 - 30 MHz continuous (including MARS and WARC bands)
• Inductor: MFJ exclusive AirCore Roller Inductor with 3-digit turns counter
• Capacitor: Differential Capacitor
• Metering: Lighted Cross-Needle meter for SWR, Forward, and Reflected Power (Peak/Average selectable)
• Meter Power: 12VDC (MFJ-1312D power supply or MFJ-5513 cable required)
• Antenna Connections: Coaxial (2), Balanced Line, Single Wire
• Dimensions: Approximately 19.75 x 13.75 x 8.5 inches (Package Dimensions)
• Weight: Approximately 9.88 pounds

9. Warranty and Support

For warranty information, technical support, or service, please contact MFJ Enterprises, Inc. directly or refer to their official website. Keep your purchase receipt as proof of purchase.

Manufacturer: MFJ