MFJ MFJ-989C User Manual

MFJ-989C VersaTuner V Instruction Manual

Introduction

The MFJ-989C roller inductor tuner is a 3000 watt These power ratings are for load impedances of 35-500 ohms. The MFJ-989C is designed to match 50 ohm output amplifiers, transmitters or transceivers to virtually any antenna. Peak and average forward power, reflected power, and SWR are displayed on the MFJ-989C's illuminated cross-needle meter.

The MFJ-989C uses a roller inductor "T" matching network. It continuously tunes all frequencies from

1.8 through 30 MHz. It will match dipoles, inverted-vee's, verticals, mobile whips, beams, random wires, and many other antennas. The MFJ-989C has rear panel connectors for coaxial and single or two wire feedlines. The

An internal six position antenna-selector switch selects a built-in 50 ohm dummy load, two coaxial line outputs, or a single wire line-balanced line output. The coaxial line outputs can be selected in tuned (with tuner's matching network in line) or direct (no matching circuit) configurations.

built-in balun

PEP

input, 1500 watt

will work with balanced open wire, twinlead, or twin-axial feedlines.

PEP

output antenna tuner.

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, and not the true RF power output. For example, the one thousand watt Johnson Matchbox was rated to handle a 1000 watt plate modulated AM transmitter (four kilowatts PEP transmitter input and 3000 watts PEP RF output). The Heathkit SB-220 was called a two kilowatt amplifier, and the rated CW output was approximately 600 watts. Matching tuners were called 2 kilowatt tuners, and these tuners safely handled 600 watts of CW power and 1200 watts PEP SSB.

The FCC has changed the power rating system of amplifiers, and tuners no longer follow amplifier power ratings. Most typical 1500 watt tuners remain able to safely handle 400-600 watts CW, and 600900 watts PEP SSB.

Load conditions and control settings also greatly affect the power handling capability of the tuner. Tnetworks typically handle more power on higher frequency bands into higher load impedances. The worst operating condition for T network tuners are low impedance capacitive reactance loads. Tnetwork tuners always handle the least power when operated on 160 meters into low impedance capacitive reactive loads.

Follow the guidelines in this manual to avoid exceeding the ratings of this tuner.

Peak Reading SWR/Wattmeter

The cross-needle meter measures the peak or average FORWARD power, REFLECTED power, and SWR. The illuminated cross-needle meter operates with the antenna tuning circuit in or out of line. The wattmeter can be used without the tuning network by setting the the two the

The meter's full scale forward and reflected power range is controlled by the left selects this switch to the switch to the

COAX DIRECT

ANTENNA SELECTOR

2000W (HI)

2000W HI

200W LO

positions of the antenna selector. The wattmeter is active in all positions of

200W (LO)

switch position (out).

(in) position. If your transmitter has less than 200 watts of output, set this

ANTENNA SELECTOR

POWER

. If your transmitter runs more than 200 watts of output power, set

to either of

switch that

MFJ-989C VersaTuner V Instruction Manual

Peak envelope power (PEP) is measured when the side) in placed in the

PEAK

(in) position. Peak power and average power values are equal with steady

PEAK

AVG POWER

push button (right-hand

unmodulated carriers, FSK, or FM. The meter reading on these modes will be the same whether the

PEAK / AVG

button is pressed or released. On SSB, the PEP meter reading should be twice the

average power with two tone test modulation. On SSB, the ratio of PEP to average power varies with different voice characteristics. With most voices,

the PEP reading is three to five times higher than the average voice power reading. The most accurate peak envelope power readings are obtained only with sustained carrier, voice or two tone test modulation. During normal voice modulation the wattmeter will typically indicate only 70% of the true peak envelope power.

Forward power is displayed on the left-hand FORWARD meter scale. This scale is calibrated from 0 to 200 watts and is read directly in the 200 watt position. Each picket (scale mark) represents 5 watts below 40 watts and 10 watts between 40 and 200 watts. In the

2000W (HI)

position the forward power scale must be multiplied by 10. Each picket represents 50 watts below 400 watts and 100 watts from 400 to 2000 watts.

The reflected power is read on the ri ght-hand REFLECTED meter scale. This scale indicates 50 watts full scale when the

200W

power sensitivity is selected, and 500 watts full scale when the

2000W

power scale is selected. This scale has a picket every watt below 20 watts and every 5 watts above 20 watts. This scale is also multiplied by 10 when using the 2000W power position.

The most accurate power readings occur in the upper half of the meter scales. When trying to measure power with a less than perfect match, the reflected power should be subtracted from the forward power reading.

The SWR is read directly from eleven red SWR curves that range from 1:1 to infinity. SWR is measured by observing the point where the forward and reflected power needles cross. The SWR is indicated by the red curve closest to the needle crossing point. No cumbersome or time consuming SWR sensitivity adjustments are required with this meter.

The wattmeter has an internal lamp that backlights the meter scale. The lamp circuit requires power from an external 12 Vdc source, such as the optional MFJ-1312B power supply. The rear panel jack accepts a 2.1 mm coaxial plug with the center conductor positive (+) and the sleeve negative (-). The negative lead is grounded inside the tuner. The

METER LAMP ON / OFF

switch turns the meter lamp

off and on.

Antenna Selector

ANTENNA SELECTOR

The

allows you to select 2 rear panel SO-239 coaxial connectors either direct

or through the tuner, a 50 ohm dummy load, and single wire or balanced feedline antennas.

MFJ-989C VersaTuner V Instruction Manual

Installation

CAUTION: Locate the tuner so the rear is not accessible during operation.

Locate the tuner in a convenient location at the operating position. If random wire or balanced line

operation is used, the ceramic feed through insulators may have high RF voltages. These voltages can cause serious RF burns if the terminals are touched when transmitting.

tuner so these terminals can not be accidentally contacted during operation.

Install the tuner between the transmitter and the antenna. Use a coaxial cable (such as RG-8/U) to

connect the transmitter (or amplifier) to the connector marked tuner.

Connect the antenna(s) to the tuner as follows:

Coaxial feedlines connect to the coax connectors 1 and 2 coax lines (fed directly or through

Random wire or single wire line antennas should be connected to the

Note C.

Any balanced feedline (open wire, twinlead, or twin-axial lines) is connected to the

A ground post is provided for an RF ground connection.

TRANSMITTER

matching circuit as selected by the

back of the unit.

Route all single and random wire antennas to prevent RF burn hazard.

BALANCED LINE

terminals. Also, connect a jumper wire where indicated.

ANTENNA SELECTOR

switch.

Be sure to locate the

on the rear of the

WIRE

connector on the

Block Diagram

Figure 1

Operation

The roller inductor has reference counter. The capacitors have simple language, as the frequency is increased, the normal control positions rotate clockwise just like on other equipment.

Note:

Always use the most capacitance (settings closest to 0) for the most power handling and the least

Note

The MFJ

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.

maximum inductance

maximum capacitance

loss. Use the smallest possible inductance (the lowest number possible) also.

Air Core

keeps potentially damaging self-resonances away from your operati ng frequency. This feature is switched in and out of the circuit with a built-in switch in the roller. Therefore, as you turn the roller up and down, you may feel a bump. This is normal and you should not be alarmed.

™ Roller Inductor is designed with an exclusive

at about 000 and

minimum inductance

at 0 and

minimum capacitance

Self-Resonance Killer

at 125 on the

at 10. In

™ that

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