MFJ MFJ-945E - User Manual

MFJ-945E Mobile Tuner
1
MFJ-945E MOBILE TUNER
General Information:
The MFJ-945E Mobile Tuner is a compact tuner designed for mobile operation in cars, trucks,
RV's, and boats. Covering
1.8
to
30 MHz
, it will match virtually any transmitter to almost any
mobile whip antenna. It will also match almost any antenna for home station operation such as
dipoles, inverted-vees, verticals, beams, random wires, and others fed by coax lines or single wire.
The MFJ-945E employs a cross-needle meter so forward power, reflected power, and SWR may
be read simultaneously. The meter lamp can be powered by a 12Vdc, 300mA source, such as the
MFJ-1312B for home-station operation. The meter lamp
ON/OFF
switch will activate the meter
lamp. Use a 2.1mm coaxial plug with the center conductor of the plug connected to the positive
and the sleeve connected to ground. Optional mobile mounting bracket (MFJ-20) is available.
Cross-Needle SWR/Wattmeter:
The MFJ-945E utilizes a cross-needle meter to read FORWARD power, REFLECTED power and
SWR simultaneously in either
HI
(300 Watts) or
LO
(30 Watts) power ranges. Set the power
range switch to
HI
or
LO
. Next read the FORWARD power on the Forward Scale. REFLECTED
power is shown at the same time on the Reflected Scale. SWR is read by observing where the two
needles cross. No SWR sensitivity adjustment 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 MFJ-945E is factory calibrated on the
LO
scale at
10
Watts FORWARD and
2
Watts REFLECTED, and on the
HI
scale at
100
Watts FORWARD and
20
Watts REFLECTED.
Installation:
1.
Place the tuner in a convenient location at the operating position. Avoid placing the tuner
near microphones, speech processors, TNC's or other RF sensitive devices.
2.
Install the MFJ-945E between your transmitter and antenna. Connect a coax line from your
transmitter to the SO-239 connector labeled
TRANSMITTER
on the rear panel of the tuner.
Connect your antenna to the SO-239 connector labeled
ANTENNA
on the rear panel of the
tuner. A random wire antenna may be connected to the center connection of the
ANTENNA
connector. 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
1/4-wavelength
or longer at the operating frequency. Do
not
ground the random wire antenna. Ensure that
the tuner is well grounded to the transmitter! A post labeled
GROUND
is provided for
ground connection(s).
NOTE:
If random wire operation is desired, position the tuner so that the rear panel terminals
can not be contacted by persons or conductors! When transmitting with random wire,
the rear panel connectors can operate with high RF voltages. These voltages may
cause serious burns and may also damage anything contacting or within 1/2" of the
terminals!

Summary

MFJ-945 E Mobile Tuner Overview

General Information

Overview of the tuner's features, capabilities, and power needs for mobile and home use.

Cross-Needle SWR;Wattmeter

Details the dual-needle meter for simultaneous power and SWR readings across different ranges.

Installation Instructions

Guides on proper placement and connection of the tuner to the transmitter and antenna systems.

Operating the MFJ-945 E Tuner

Tuning Procedure

Step-by-step guide to tuning the MFJ-945E using INDUCTOR, TRANSMITTER, and ANTENNA controls for minimum SWR.

Safety and Tuning Warnings

Crucial safety advice to never transmit while changing the INDUCTOR setting and to avoid arcing.

Troubleshooting and Antenna Matching

Troubleshooting Common Issues

Provides solutions for tuning failures, arcing, and general advice for optimal tuner performance.

Antenna Matching Problems

Discusses challenges with high impedance antennas and feedline lengths, offering solutions for better matching.

Antenna Matching Suggestions

Offers specific tips and feedline length guidelines to simplify matching various dipole antennas with the tuner.

Technical Assistance

MFJ MFJ-945E Specifications

General

Brand	MFJ
Model	MFJ-945E
Category	Tuner
Language	English