MFJ MFJ-1922 User Manual

MFJ-1922 Screwdriver

Antenna Controller

with counter

The MFJ-1922 is designed to give up/down control to tune
most screwdriver type antennas. This unit is compact and
ideal for mobile installation (H 2 ¾’’, W 4’’, D 1½’’). It
features a counter to count turns of the motor inside the
antenna. The four-digit readout makes tuning easier by
enabling you to return your antenna to a desired position.
Your antenna must have a sensor installed in it for the readout
to work. If your antenna does not already have a sensor
installed, contact your antenna manufacturer or MFJ.

Installation

The MFJ-1922 can be easily connected. For mobile
installations, disconnect power at the battery, until installation
is complete. Connect power to your MFJ-1922 using the red
(+12Vdc) wire and the black (GND) wire. The red (+12) wire
should be connected to your vehicle battery (or 12Vdc source)
through an inline fuse (not included). Consult your antenna
manual or manufacturer for an appropriate fuse value;
normally a 5 to 10 Amp slow blow will work. Connect the
black (GND) wire to your vehicle (or station) ground.

The remaining four wires connect to your screwdriver
antenna. Two for motor control, and two for the motor
sensor. You will need to splice wires onto each of these four
wires, so that they will reach your screwdriver antenna. Use
quality insulated wire for these extensions. The motor control
wires (green and yellow) should be no smaller than 18 AWG,
and the sensor wires (brown and white) should be no smaller
than 24 AWG. Take care and follow your antenna
manufacturers suggestions about routing these wires for a
mobile installation. Connect the motor control wires and
sensor wires to the antenna. There is no polarity on the brown
and white sensor wires. If the motor travels in the wrong
direction, switch the polarity of the green and yellow motor
control wires. This control unit is designed to operate with a
screwdriver antenna that operates on 12 volts. Many antennas
operate on only 3 or 4 volts, a Dropping Resistor is used inline
with the motor control line to bring the voltage down.
Consult your antenna manual or manufacturer for the
operating voltage. See the section Dropping Resistor for
more details.

WARNING: The MFJ-1922 is designed for
screwdriver antennas that operate on 12 volts.
Many antennas operate on only 3 or 4 volts, a
Dropping Resistor is used inline with the motor
control line to bring the voltage down. Consult your
antenna manual or manufacturer for the operating
voltage. A mismatched voltage could severely harm
your antenna. See the section Dropping Resistor for
details.

Calibration and Operation

The MFJ-1922 will need to be calibrated to your antenna.
First, turn ON the power to the MFJ-1922 and press the motor
control rocker switch DOWN until your antenna is fully
collapsed. Then switch OFF the power to the MFJ-1922.
Next, press DOWN on the motor control switch WHILE
switching ON the power to the MFJ-1922. The display will
then read zero. The up/down switch may now be used to tune
your antenna to resonance on the desired operating frequency.
Consult your transceiver/antenna manual or manufacturer for
more operating and tuning procedures. Typically an SWR of

1.5 or less is acceptable.
Due to the nature of some screwdriver antennas they will
coast a few turns after power has been removed. This
coasting can be observed on the display. Allow a coast time
of one or two seconds before switching directions. Avoid
rapidly switching directions of the antenna. Rapidly
switching directions will uncalibrate the counter on the MFJ-

1922. If the counter does not read zero when the antenna is
fully collapsed, the counter will need to be recalibrated as
described above. Recalibration should be done periodically
due to vibrations in a mobile environment.
The counter on the MFJ-1922 is an aid to help you quickly
tune your antenna. Fine-tuning will be necessary. Use the
counter to bring your antenna back to a certain portion of a
band.

Dropping Resistor

The MFJ-1922 is designed to work with screwdriver antennas
that operate with 12 Vdc. Many antennas operate on only 3 or
4 volts, a Dropping Resistor is used inline with the motor
control line to bring the voltage down. Consult your antenna
manual or manufacturer for the operating voltage of your
antenna. If a dropping resistor is necessary, a good value to
try is 5 Ω/10 Watts.
on one of the motor control lines anywhere in between the
MFJ-1922 and the antenna. If you are not sure whether or not
this resistor is necessary for your antenna, try it and inspect
the torque and speed of the motor. If the motor is too slow,
reduce or eliminate the resistance. Use of 12 volts with a 3 or
4 volt antenna will result in failure of the motor.

This resistor will need to be placed inline

Technical Assistance

If you have any problems with this unit, please read the
manual again. If the manual does not reference your problem
or your problem is not solved by reading the manual you may
call MFJ Technical Service at 662-323-0549 or the MFJ
Factory at 662-323-5869.

You can also send questions by mail to MFJ Enterprises, Inc.,
300 Industrial Park Road, Starkville, MS 39759; by FAX to
662-323-6551; or by email to [e-mail].
Send a complete description of your problem, an explanation
of exactly how you are using your unit, and a complete
description of your station.