MFJ-1922B Screwdriver
Antenna Controller
with counter
motor control
The MFJ-1922B 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.
Antennas that do not have a 4 pin plug. The plug can be cut
off. Use the chart below for wire color and its function.
Controller with six wires
The MFJ-1922B can be easily connected. For mobile
installations, disconnect power at the battery, until installation is
complete. Connect power to your MFJ-1922B 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. Avoid routing
control wires with the feed line. Make sure a RF choke is placed
around the control lines at the antenna. 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.
Installation (B)
Controllers that have the 4 pin Molex plug.
The red wire needs to be fused and connected to the
vehicle’s +12 VDC supply. The size of the fuse depends
upon the current requirement of the antenna motor.
Typically a 5 Amp slow-blow fuse will work. Some
installations may require additional wire. Use 16 AWG
wire to add additional length.
2. The black wire needs to be connected to the vehicle
(station) ground.
If the supplied red and black wires are not long enough,
Use 16 AWG wire to add additional length.
3. Connect the 4 pin Molex to the antenna.
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
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.
mismatched voltage could severely harm your antenna.
See the section Dropping Resistor for details.
The MFJ-1922B will need to be calibrated to your antenna. First,
turn ON the power to the MFJ-1922B and press the motor control
rocker switch DOWN until your antenna is fully collapsed. Then
switch OFF the power to the MFJ-1922B. Next, press DOWN on
the motor control switch WHILE switching ON the power to the
MFJ-1922B. 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.
Setup Menu Flow
Hold Menu button + Power On Trip Current (C) Relay Delay (d) Set UP Normal Operation
After entering setup, the setting and the value are displayed.
Pressing Up or Down changes the value.
. After the end is reached the last value is saved and the controller
continues with normal operation.
Trip Current
This is shown in the menu with a “C” in the left-most digit. The
other 3 digits will display the currently selected value. The trip
current value is used to determine when the motor has stalled and
immediately shuts the motor off. This feature protects the motor
from damage if the antenna becomes stalled. The current is
displayed as Cxxx, which translates into x.xx amps. The default
setting is C075 or 0.75 amps. This is also the setting for use with
the Ameritron SDA-100 Screwdriver Antenna.
Relay Delay
This setting controls the amount of time the relays are reversed
when the motor is stopped. When the motor is stopped, the relay
that was moving the motor is deactivated and the opposite relay is
activated for the duration set in the menu. The default setting is
20ms. The values range from 0ms – 200ms.
This determines which button will move the antenna up. This can
also be used to move the antenna correctly if the motor terminals
are reversed. When UP is on the display, press the corresponding
button (Up or Down), which moves the antenna up. This is then
saved to memory. Pressing any other key will not make any
changes and simply exit setup. Since this is the last setting in the
setup menu. The controller will proceed with normal operation.
Consult your transceiver/antenna manual or manufacturer for
more operating and tuning procedures. Typically an SWR of 1.5
or less is acceptable.
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-1922B 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.
The MFJ-1922B 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. This resistor will need to be placed inline on one of the
motor control lines anywhere in between the MFJ-1922B 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.
If you have any problems with this unit, please read the
instructions again. If the instructions does not reference your
problem or your problem is not solved by reading the instructions
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 662-3236551; or by email to Send a
complete description of your problem, an explanation of exactly
how you are using your unit, and a complete description of your
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