MFJ VERSA TUNER III User manual

MFJ VERSA TUNER III
MODEL MFJ-9628
OWNER'S MANUAL
..
CAUTION: Read All instructions Before Operating Equipment.
MFJ ENTERPRISES, INC.
P. 0. BOX 494, MISSISSIPPI STATE, MS. 39762, USA

INTRODUCTION
The MFJ-962B VERSA TUNER III is an antenna tuning unit de-
signed for use in Amateur transmitting systems. The tuner
is designed to match most antenna systems from 1.8 to 30 MHz,
and will handle 1.5 KW PEP RF output power.
SWR/WATTMETER
The cross needle meter is easy to use. To read FORWARD
power, set the POWER switch to Hi or Lo then read the power
level on the forward scale. Maximum power reading on the Hi
scale is 2KW and Maximum power reading for the Lo scale is
200W. Reflected power con be read from the reflected power
scale. SWR is indicated by the SWR line where the two needles
crossed. No SWR sensitivity adjustment is needed to read SWR.
ANTENNA SELECTOR
The ANTENNA SELECTOR switch allows the selection of two coax
fed antennas through the tuner or direct, a balanced line/
wire antenna, and a coax bypass position. The balanced line
circuit employs a 4:1 balanced to unbalanced transformer (balun)
specially designed to minimize the power loss and give good
frequency response. The balun uses a high permeability fer-
rite toroid core with a minimum number of turns to give both
good low frequency and high ferquency response.
INSTALLTION
1. Locate the tuner in a convenient location at the operating
position. NOTE: LOCATE THE TUNER SO THAT THE REAR OF THE
TUKER IS NOT ACCESSIBLE DURING OPERAT~ON.
2. Install the tuner between the transmitter and the antennas
as shown in the diagram. Use coax cable such as RG-8/U
between the transmitter output and the S0-239 connector
marked TRANSMITTER on the tuner.
(OPTIONAL}
SWRIWATl
EXCITER
AF AMP. MFJ-8828
METER
J
I I I
__._
3. Connect the antenna(s) to the tuner as follows:
A. Coax cable feed lines to the coax connectors. Up to
two coax lines may be connected to the tuner at the
same time.
B. Balanced feed lines are connected to the terminals
marked BALANCED LINE.
y
C. Random wire antennas or single wire lines are connected
to the WIRE terminal. Install a jumper between the
binding posts as marked on the tuner when using wire ant.
NOTE: ROUTE ALL SINGLE WIRE AND BAL. LINES TO PREVENT
RF BURN HAZARD.
1

cont.
4. Ground the tuner to the transmitter, amplifier. and earth GND.
OPERATION
The INDUCTOR switch on the MFJ-962B has a minimum inductance
at position A and maximum at L. The ANTENNA MATCHING and
TRANSMITTER MATCHING controls are at maximum capacitance when
set to 10. For optimum operation of the MFJ-962B, tune the
exciter into a 50 ohm load. For convenience connect the ex-
ternal 50 ohm load to one of the coax outputs so the exciter
will not have to be disconnected when it is tuned up.(use
COAX BYPASS)
Follow these steps for proper tuning:
1. Tune the exciter up into a dummy load. (Most solid state
transmiters are pretuned to 50 ohms and do not require
tuning up into a dummy load.)
2. Select the desired antenna with the ANTENNA SELECTOR.
3. Set the ANTENNA and TRANSMITTER MATCHING controls to about 4.
4. Starting from minimum on th INDUCTOR, tune for maximum
noise and signals.
5. With the linear amplifier OFF or in stand-by, set the
meter power switch to Lo range and transmit a low power
signal(10 to 50 watts).
6. Adjust the ANTENNA and TRANSMITTER MATCHING controls for
minimum. If SWR is not 1:1 adjust the inducto up or down
and repeat Step 6. If the capacitors are at maximum cap-
acitance, increase the inductance. If the capacitors are
at minimum capacitance, decrease the inductance.
7. After minimum SWR is achieved the amplifier may be turned
on and tuned up according to the manufacturer's instructions.
8. For quick retuning of the tuner, record the INDUCTOR and
CAPACITOR settings.
OPERATING NOTES
1. Even though this tuner is designed to have as large a tuning
range as possible, it may not always be possible to tune
an antenna system to a 1:1 SWR. A SWR of 1.5:1 to 2:1 is
usually acceptable to most transmitters (see your transmitter
instructions.) If a higher SWR is not acceptable there are
several things which can be tried. For example, if the
antenna is very short try lengthening it. A loading coil
or a capacitive hat may also help raise the impedence to
within the tuner range.
2. A SWR of 1:1 Can occur for more than one control setting.
If this should occur use the setting which gives the highest
received signals and noise.
WARNING
1. NEVER OPERATE THE TUNER WITH THE COVER REMOVED. THE VOLTAGES INSIDE ARE VERY DANGEROUS
DURING OPERATION.
2. NEVER ROTATE THE "INDUCTOR" OR THE "ANTENNA SELECTOR" SWITCH WHILE OPERATING, DAMAGE
TO
THE SWITCH MAY RESULT.
3. LOCATE THE TUNER SO THAT IT WILL NOT
BE ACCESSIBLE FROM THE REAR.
4. DISCONNECT THE ANTENNAS FROM THE TUNER DURING LIGHTING
AND STORMS.
5. ALWAYS TUNE WITH LOW POWER (i.e. LESS THAN 100 WATIS). APPLY MAXIMUM POWER ONLY AFTER TUNING.
6. DO NOT KEY TRANSMITTER INTO HIGH SWR FOR LONG PERIODS OF TIME.
2

cont.
-------~
TRANSMITTER
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SW2A}r-----------------------~'~,----~
CE
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~JACK
MFJ-9628
SCHEMATIC DIAGRAM
POS
1
2
3
4
5
8
-, WIRE/BAL. LINE
ANTENNA SEL.
COAX2DIR.
COAX1 DIR.
COAX1
COAX2
WIRE/BAL. LINE
COAX BYPASS