MFJ MFJ-941E User Manual Download Page 2

MFJ-941E Versa Tuner II

2

INSTALLATION:

1.

The tuner should be placed in a location where operation will be convenient.  The ceramic
feed through insulators will have high RF voltages if random wire or balanced line
operation is used.  These voltages can cause serious RF burns if touched when
transmitting.

NOTE
:

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

2.

The 

MFJ-941E

 should be installed between the transmitter and antenna.  A coaxial line

should be connected to the transmitter and the SO-239 coax 

TRANSMITTER

 connector

on the back of the tuner.

3.

One or two coax-fed antennas may be connected to the SO-239 coax connectors marked

COAX 1

 or 

COAX 2

.  Coax 1 and Coax 2 antennas may be connected directly to the

transmitter, bypassing the tuner, by setting the 

ANTENNA SELECTOR

 switch to 

COAX 1

DIRECT

 or 

COAX 2 DIRECT

, respectively.

4.

A random wire antenna may be connected to the five-way binding post marked 

WIRE

.

The random length wire should be long, high, and as clear of surrounding objects as
possible.  For optimum operation, the wire antenna should be a quarter wave-length or
longer at the operating frequency.  Do NOT ground the random wire antenna.  The tuner
should be well-grounded to the transmitter.  A binding post marked 

GROUND

 is provided

for ground connections.

5.

A balanced line-fed antenna may be connected to the two five-way binding posts marked

BALANCED LINE

.  A jumper wire from the 

WIRE

 binding post, as indicated by a dotted

line on the 

MFJ-941E

, should be connected to one of the posts of the 

BALANCE LINE

.

This couples the 

MFJ-941E

 to the balanced line through a 4:1 balun.

NOTE
:

Either a balanced line or a random wire antenna may be connected to the 

MFJ-941E

 at

one time.  If a random length wire is used, care should be taken to assure that no
jumper wire is between the 

WIRE

 binding post and the 

BALANCED LINE

.

6.

An external 50 Ohm dummy load may be connected to the 

EXT. DUMMY LOAD

connector located at the rear of the tuner.

Summary of Contents for MFJ-941E

Page 1: ...vel on the FORWARD SCALE REFLECTED power is shown simultaneously on the REFLECTED SCALE SWR is determined by observing the intersection point of the two needles No SWR sensitivity adjustment is needed to read SWR The HI range is 300 Watts FORWARD and 60 Watts REFLECTED The LO range is 30 Watts FORWARD and 6 Watts REFLECTED The difference between the HI and LO scales readings is a factor of 10 The ...

Page 2: ...e connected to the five way binding post marked WIRE The random length wire should be long high and as clear of surrounding objects as possible For optimum operation the wire antenna should be a quarter wave length or longer at the operating frequency Do NOT ground the random wire antenna The tuner should be well grounded to the transmitter A binding post marked GROUND is provided for ground conne...

Page 3: ... be set to DUMMY LOAD for tuning up the transmitter NOTE The transmitter should always be tuned at a low output power After the transmitter is properly tuned the ANTENNA SELECTOR should be set to the desired antenna and the tuner adjusted for a minimum SWR as described below DO NOT readjust the transmitter loading control setting after loading it to 50 Ohms NOTE When using the MFJ 941E for receivi...

Page 4: ...adjust TRANSMITTER and ANTENNA controls for minimum SWR Since both controls interact the two controls can best be adjusted by turning the TRANSMITTER control one small increment at a time then rotating the ANTENNA control for minimum SWR Repeat this process until minimum SWR is obtained ...

Page 5: ...cedures again Be sure you are using enough inductance lowest letter usable for band and have the capacitors open far enough highest front panel number If this tuner arcs at the rated power levels please double check all connections and follow the tuning procedures again Be sure you are using the least amount of inductance and the greatest capacitance possible to match the load on the operating fre...

Page 6: ...n wire line is used to feed a half wave 100 to 140 foot dipole The odd quarter wave line transforms the dipole s low impedance to over three thousand Ohms at the tuner This is because the mismatched feedline is an odd multiple of 1 4 wavelength long The line inverts or teeter totters the antenna impedance ...

Page 7: ...d these lengths The worst possible line lengths are shown in brackets 160 meter dipole 35 60 170 195 or 210 235 feet Avoid 130 260 ft 80 meter dipole 34 40 90 102 or 160 172 feet Avoid 66 135 190 ft 40 meter dipole 42 52 73 83 112 123 or 145 155 feet Avoid 32 64 96 128 ft NOTE Some trimming or adding of line may be necessary to accommodate higher bands WARNING To avoid problems a dipole antenna sh...

Page 8: ... INC P O Box 494 Mississippi State MS 39762 by FAX to 601 323 6551 through Compuserve at 76206 1763 or by email to 76206 1763 Compuserve com Send a complete description of your problem an explanation of exactly how you are using your unit and a complete description of your station ...

Page 9: ...MFJ 941E Versa Tuner II 9 Schematic ...

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