MFJ MFJ-962D User Manual
MFJ-962D Instruction Manual
Introduction
The MFJ-962D is a "T" network roller inductor tuner with built-in antenna switching, RF power and
SWR metering and a 1:1 balun. The largest amplifiers that can safely be used include the Heathkit SB200 and 201, Collins 30L1, and Ameritron's AL-600 and AL-811 series of amplifiers. This tuner is
designed for maximum RF output power levels of 800 watts carrier or PEP on 80-10 meters, and 500
watts carrier or PEP on 160 meters. It 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 wattmeter's illuminated cross-needle meter.
The MFJ-962D 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 built-in balun will work with balanced open wire, twinlead, or
twin-axial feedlines.
An internal six position antenna-selector switch selects two separate coaxial line outputs either in tuned
(with tuner's matching network in line) or direct (no matching circuit) configurations, a balanced line
output, and a coax bypass position for accessories such as an external dummy load. Long wire antennas
can be connected to the center connector of the coax connector.
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.
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 ANTENNA SELECTOR to either of
the two COAX DIRECT positions of the antenna selector. The wattmeter is active in all positions of
the ANTENNA SELECTOR.
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MFJ-962D Instruction Manual
The meter's full scale forward and reflected power range is controlled by the left POWER switch that
selects 2000W (HI) or 200W (LO). If your transmitter runs more than 200 watts of output power, set
this switch to the 2000W HI (in) position. If your transmitter has less than 200 watts of output, set this
switch to the 200W LO switch position (out).
Peak envelope power (PEP) is measured when the PEAK or AVG POWER push button (right-hand
side) in placed in the PEAK (in) position. Peak power and average power values are equal with steady
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 indicates 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
readings.
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
on and off.
Antenna Selector
The ANTENNA SELECTOR allows you to select 2 rear panel SO-239 coaxial connectors, either direct
or through the tuner, a coax bypass output, and balanced feedline antennas.
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MFJ-962D Instruction Manual
Installation
CAUTION: Locate the tuner so that the rear panel is not accessible during op eration.
1. Locate the tuner in a convenient location at the operating position. If 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. Be sure to locate the tuner so that these
terminals can not be accidentally contacted during operation.
2. Install the tuner between the transmitter and the antenna as shown in the diagram below. Use a
coaxial cable (such as RG-8/U) to connect the transmitter (or amplifier) to the connector marked
TRANSMITTER on the rear of the tuner.
3. Connect the antenna(s) to the tuner as follows:
A. Coaxial feedlines connect to the coax connectors 1 and 2 coax line (fed direct or through
matching circuit as selected by the ANTENNA SELECTOR switch).
B. Random wire or single wire line antennas should be connected to the center of the COAX 1 or
COAX2 SO-239 connectors. Select the appropriate Coax position to use the antenna.
Note: Route all single and random wire antennas to prevent RF burn hazard.
C. Any balanced feedline (open wire, twinlead, or twin-axial lines) is connected to the
BALANCED LINE terminals.
4. A ground post is provided for an RF ground connection.
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Block Diagram
Figure 1
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