1. Introducció
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. Informació de seguretat
- 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. Producte acabatview
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).
Controls del panell frontal:
- 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 Interruptor (ON/OFF): Controls the illumination of the meter.
4. Configuració
- Connexió d'alimentació: 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.
- Connexió del transceptor: Connect the output of your transceiver to the "TRANSMITTER" SO-239 connector on the rear panel using a high-quality 50-ohm coaxial cable.
- Connexió d'antena:
- 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.
- Connexió a terra: 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. Instruccions de funcionament
5.1 Initial Power-Up and Metering
- Assegureu-vos que totes les connexions siguin segures.
- Turn on the 12VDC power supply for the meter.
- Estableix el Lamp canviar a ON if illumination is desired.
- Seleccioneu l'opció adequada Interval (HI for high power, LO for low power) and Poder (PK for peak, AVG for average) settings for your operating conditions.
5.2 Procediment d'afinació
The MFJ-986 is designed for easy tuning, often requiring only one setting for minimum SWR due to its differential capacitor.
- Select Antenna: Estableix el Interruptor selector d'antena 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.
- Configuració inicial:
- Estableix el Differential Capacitance knob to a mid-range position (e.g., 5).
- Estableix el Inductance Roller to a mid-range value (e.g., 150 on the counter).
- 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).
- Adjust Inductance: Gireu lentament Inductance Roller while observing the SWR meter. Find the point where the SWR reading is lowest.
- Adjust Capacitance: Gireu lentament Differential Capacitance knob while observing the SWR meter. Adjust for the absolute minimum SWR.
- Afinar: Make small, alternating adjustments to both the Inductance Roller i Differential Capacitance knob until the lowest possible SWR is achieved. The goal is to reach 1:1 SWR if possible.
- 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.
Nota: 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. Manteniment
- Neteja: Keep the tuner clean and free of dust. Use a soft, dry cloth for cleaning the exterior. Do not use abrasive cleaners or solvents.
- Connexions: Periodically check all coaxial and binding post connections to ensure they are tight and free from corrosion.
- Inspecció interna: 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.
- Emmagatzematge: Store the tuner in a dry, temperature-controlled environment when not in use.
7. Solució De Problemes
- No Meter Illumination:
- Ensure 12VDC power is connected and switched on.
- Comproveu el Lamp l'interruptor està al ON posició.
- 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.
- Verifiqueu el Interruptor selector d'antena is set to the correct position for your connected antenna.
- Confirm a good RF ground connection.
- Assegureu-vos el Interval 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.
- Confirmeu el Interval switch is set correctly.
8. Especificacions
- Model: MFJ-986
- Tipus de sintonitzador: Differential-T, Roller Inductor
- Potència nominal: 3KW PEP SSB amplifier input power (1500 Watts PEP SSB output power)
- Cobertura de freqüència: 1.8 - 30 MHz continuous (including MARS and WARC bands)
- Inductor: MFJ exclusive AirCore Roller Inductor with 3-digit turns counter
- Condensador: Differential Capacitor
- Mesurament: Lighted Cross-Needle meter for SWR, Forward, and Reflected Power (Peak/Average selectable)
- Potència del comptador: 12VDC (MFJ-1312D power supply or MFJ-5513 cable required)
- Connexions d'antena: Coaxial (2), Balanced Line, Single Wire
- Dimensions: Aproximadament 19.75 x 13.75 x 8.5 polzades (dimensions del paquet)
- Pes: Aproximadament 9.88 lliures
9. Garantia i Suport
For warranty information, technical support, or service, please contact MFJ Enterprises, Inc. directly or refer to their official weblloc web. Conserveu el rebut de compra com a comprovant de compra.
Fabricant: MFJ





