MFJ MFJ-941E User manual

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MFJ V RSA TUNER II
M·O·DE MFJ-941
INSTRUCTION ANUAL
C.AUTl·ON: Read AU Instructions Before Operating Equipment
MFJ ENTERPR SES, INC.
P.O.BOX 494, MISSISS,IPPI STATE, MS 397· 62 , USA
COPYRIGHT 1991 I MFJ ENTERPRISES, INC.

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MFJ-941E VERSA TUNER .ll INSTRUCTION S
GENERAL INFORMATION
The MFJ -941E is designed to match virtually any transmitter
t o almost any antenna, including dipoles, inverted-vees,
verticals, mobile whip s , beams, random wires , and othe r s fed
by coax line s, balanced lines, or a single wire. A 4:1
balun is built-in fo r connection to ba l anced lines. An
antenna-selector sw it ch provides versatile an te nna
selection . The MFJ -941E wi ll handle up to 300 watts of RF
output power f r om the transmitter f r om 160 th rough 10
me ter s. The MFJ -941E employs a cr oss -nee dle meter so
forward power, re f le cted power and SWR may be read
simulta ne ous ly.
CROSS NEEDLE SWR / WATT METER
The meter on the MFJ-941E may be used with the tuner or by
itse lf. To use the meter without the tune r, set the ANTENNA
SELECTOR to COAX 1 DIRECT or COAX 2 DIRECT . Th e MFJ -941E
utilizes a cr oss-need l e mete r FORWARD power, REFLECTED power
and SWR may be re ad simultaneous l y in two r anges . To read
FORWARD power, set the power range sw it ch t o HI(300 watts)
or L0(30 watts). Next r ead the power level on the FOR WARD
SCALE. REFLECTED power is shown at the same time on the
REFLECTED POWER SCALE . SWR is r ead by obse rv ing where the
two needles cr oss . No SWR se n sitivity adjustment is needed
to rea d SWR . Read the power level off of both scal es . The
HI ran ge is 300 wa tts FORWARD and 60 watts REFLECTED . The
LO r an ge is 30 watts FORWARD and 6 w atts REFLECTED . The
difference between the HI and LO sca l es r eadings is a factor
of 10.
The
mete r lamp can be powe re d by a 1 2V DC sou r ce, such as
the optional MFJ - 1312 power supply. Use a 2.5mm pl ug with
t he t ip of the p lu g co nn ected to the positive. The METER
LAMP ON/OFF switch will activa t e the meter lamp.
ANTENNA SELEC TOR
The ANTENNA SELECTOR switch a ll ows selecting two coax
antennas eithe r directly or through the tuner, a balanced-
line antenna, a wire antenna . An external 50 ohm dummy load
ca n be co nne cted t o the EXT . LOAD co n necto r located at the
rear of the tune r . Do not co ntinuously key into the dummy
load for more than 2 minutes at a time. CAUTION: DO NOT
OPERATE THE ANTENNA SE L ECTOR SWITCH WHILE TRANSMITTI NG.
Never
use the MFJ -948 for~ JOO watt s of RF output power,
~ in the DIRECT or DUMMY LOAD positions.
1

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INSTAL L ATION
1. Locate the tuner in a convenient location at the
operating position. N OTE: LOCATE THE TUNER SO THE REAR
IS N OT A CCESS I BLE DURI NG OPE RA TION . If random wire or
balanced line operation is used , the ce ramic fe ed
th r ough insu l ators wil l have high RF voltages which can
cause serious RF burns if touched when t r ansmitting .
2. In sta l l the MFJ -941E between the t r ansmitter and antenna
as shown in the diag r am above . A coax line is connected
to the t r ansmitte r and the S0-239 coax connector marked
TRANSMITTER on the back of the tuner.
3. One or two coax - fed antennas may be connected to the S0-
239
coax connectors marked COAX 1 or COAX 2. NO TE: Coax
1 and Coax 2
antennas may be connected di r ectly to the
t r ansmitte r , bypassing the tuner , by setting the ANTENNA
SELECTOR switch to COAX 1 DIRECT or COAX 2 DIRECT
r espectively .
4. A r andom
wire antenna may be connected to the five way
binding post ma r ked WIRE . The random length wire should
be l ong, high, and as clear of sur r ounding objects as
possible. Fo r optimum operation , the wire antenna
should be a quarter - wavelength or longer at the
operating frequency . Do NOT ground the random wire
antenna . Make ce r tain that the tuner is well - gr ounded
to the transmitter. A binding post marked GROUND is
provided for ground connection(s).
5. A balanced line fed antenna may be connected to the two
five w ay binding posts marked BAL ANCED LINE. A jumper
wire from the WIRE binding post , as indicated by a
dotted line on the MFJ - 941E, shou l d be connected to one
of the posts of the BALANCED LINE. This couples the
MFJ-941E to the balanced line through a 4:1 balun.
NOTE : E ither a balan c ed line or a rand om wire antenn a
m
ay be conne c te d t o the MFJ -941E at one time. If a
r andom
len gt h w ire i s used, make sure t h at t here is no
jum
per wire bet w een the WI RE an d B ALA NCE D L INE binding
po sts .
6. An external 50 ohm dummy load maybe connected to the
EXT. DUMMY LOAD connector located at the rear of the
tune r.
2

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USING THE MFJ-941E
The
INDUCTOR switch on the MFJ -941E represents minimum
inductance at position A and a maximum indu c tance at
position L. Less inductance is needed at higher frequencies
than at low frequencies for the same impedance. The
TRANSMITTER and ANTENNA controls both represent maximum
capacitance at position 10. Fo r optimum operation of the
MFJ-948, the transmitter must be tuned to a 50 ohm output
impedance at the frequency of operat ion. Set the ANTENNA
SELECTOR switch to DUMMY LOAD for tuning up the
transmitter.NOTE: Always tune the transmitter at a low
output power.
After properly tuning the transmitter, set ANTENNA SELECTOR
to the desired antenna and tune the tuner for a minimum SWR
as described below. Do NOT read just the transmitter loading
control setting after loading it to a 50 ohm load .
1. Set the TRANSMITTER and ANTENNA controls to 5. The
capacitors are h alf-opened .
2.
Rotate the INDUCfOR cont r ol until maximum noise is
obtained with your transceiver in the receiving mode.
3. While transmitting a steady state carrier (CW)
alternately adjust '' TRANSMITTER " and "ANTENNA" cont rols
for minimum SWR . Since both controls interact, the two
controls can best be adjusted by turning the TRANSMITTER
control a small increment at a time, then rotating the
ANTENNA control for minimum SWR . Repeat until minimum
SWR is obtained .
4. If a SWR of 1 :1 is not achieved, increase or decrease
the INDUCTOR control and repeat Step 3. If arcing
should occur between capacitor plates, increase or
decrease the INDUCTOR contro l one position, then repeat
Step 3. NOTE: If you can't achieve a SWR of 1:1, repeat
Step 3 for each INDUCTOR control position .
5. After minimum SWR is achieved , transmitter power may be
increased to 300 watts. Your VERSA TUNER II will red uce
the SWR of most feed systems to 1:1. In some cases, a
1:1 SWR is not achievable. Increase or decrease the
length of your antenna to improve SWR.
6. A SWR of 1:1 may occur at more than one set of control
settings on your MFJ - 9 41 E. When an SWR of 1:1 is
obtained, check transmitter power. I nsure that
transmitter power is relatively high . If transmitter
power has decreased substantially, try anothe r INDUCTOR
control setting and repeat Step 3.
7 . When using the MFJ -941E for receiving only, tune the MFJ -
941E
as described in S tep 1 and S tep 2.

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MFJ-941E SCHEMATIC
DIAGRAM
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MFJ Enterprises, i nc . warrants to the original owner of this product, If manufactured by
MFJ Enterprlses. Inc . and purchased from an authorized dealer or directly from MFJ
Enterprises, Inc.
to be free of defects In material and workmanship for a period of 12
months from date of purchase provided the follc:rMng terms of this wamwity an satisfied.
1. The purchaser must retain the dated proof-of-purchase (bil of sale, canceled check ,
credit card or money order receipt, etc .) deacribing the product to establish the va-
lidi
ty of warranty claim and must submit the original or a machine-reproduction of
such proof -o f-purchase to MFJ Enterprises, Inc. at the time of warranty service.
MFJ Enterprises, Inc. shall have the discretion
to deny warranty without dated
proof-of-purchase. Arly evidence of alteration, erasure,
or forgery of proof-of-purchase
shall
be cause to void any and all warranty terms immedlately.
2. MFJ Enterprises, Inc. agrees to repair or replace at MFJ 's option without charge to
the original
owner any defective product provided the product is returned postage
prepaid to MFJ Enterprises, Inc. with a personal check, cashier's
chec k or money
order for $4 . 00 covering postage and handling.
3. MFJ Enterprises, Inc. will supply replacement parts free of charge for any MFJ pro-
duct under warranty upon request. A dated proof- of -purchase and a 14 . 00 personal
check, cashier's
check or money order must be prov ided to cover postage and
handling.
4. This warranty Is NOT void for owners who attempfto re~ defective units. Techni-
cal consultation is available by calling [phone] .
5. This warranty does not apply to kits sold or manufactured by MFJ Enterprises, Inc.
6. Wired and tested PC board products are covered by this warranty provided only the
wired
and tnted PC board la returned. Wired and tested PC boards installed in
the owner's cabinet or connected to switches, jacks, cables, etc . sent to MFJ Enter-
prises, Inc. will
be returned at the owner's expense unrepaired.
7. under no circunstances Is MFJ Enterprises, Inc. liable for consequential damages to
person
or property by the use of any MFJ product.
8. OuHf.Warranty Service: MFJ Enterprises, Inc. will repair any out-of-warranty pro -
duct provided the unit is delivered prepaid. All charges will be shipped COD to the
owner.
9. Thia warranty la given in lieu of any other warranty express or implied.
10 .
11.
MFJ Enteri:,taea , Inc. reserves th9 right to make changes or improvement in design
or manufacture without Incurring any obligation to install such changes upon an-1 of
the products previously manufactured.
Al MFJ PR)CllCts to be 98f-v6oed ln-wwnny or out-of-warranty should be addressed
to
IFJ Enlllp;l ■ N, Inc., t21A Loulnllle Road, Starbllle, Mlululppl 31759 , USA
and muat be accompanied by • letter describing the problem in detail along with a
copy of ycu dated proof•of-purchaae.
12 . This warranty gives you specific rights , and you may also have other rights which
vwy from state to state.