MFJ -945E User Manual

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 10Watts FORWARD and
2Watts REFLECTED, and on the HI scale at 100Watts FORWARD and 20Watts 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!
MFJ-945E MOBILE TUNER
MFJ-945E Mobile Tuner
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