MFJ-441 Instruction Manual
SlimLine Econo Keyer
1
Introduction
The MFJ-441 SlimLine™ Econo Keyer with Memory is a microprocessor controlled keyer that pro-
vides iambic key operation and dot-and-dash memory to make sending perfect code easier. It has
tuneable code speed, code weight, and sidetone frequency; it supports both direct and grid-block
keying outputs. You also get to choose between Iambic Type "A" and Type "B" keying. It even has
a volatile memory to record and play a message of your choice.
Control Functions
1. The Power button turns the unit ON and OFF. The power is ON when the button is locked in
the "in" position and OFF in the "out" position.
2. The Semi-Auto/Auto button allows semi-automatic "bug" and manual operations. The keyer
generates dots automatically when a squeeze or single lever key is used. Dashes are manually
made. The keyer is completely manual when a straight key is used. Semi-Auto is active when
the switch is in the "in" position and Auto when in the "out" position.
3. The Message button lets you record and play a message from the volatile memory. It is a mo-
mentary push-button that is time sensitive.
4. The Speed control varies the code speed. The speed range is configured with an internal
jumper (JMP 9) for 5 to 65 WPM or 10 to 40 WPM. Turn the control clockwise to increase
speed and counter-clockwise to decrease speed. The unit is factory set to 5 to 65 WPM. To
make the speed adjustment less sensitive, change the speed range to the narrower range of
10 to 40 WPM. To change the speed range the power must be off, then remove the cover by
removing the two screws (one on each side) that secure it. Locate jumper JMP 9 and set it to
the "H" position.
Note: Power must be off when changing the jumper settings.
5. The Weight control varies the code weight from approximately 25 % to 75 %, with the stand-
ard dot defined as 50 % weight. The standard dot-dash-space ratio is 1:3:1 (trimpot at mid-
range). Turn the control clockwise to increase dot and dash lengths and counter-clockwise to
decrease dot and dash lengths. This control is located internally. When looking at the unit's
front panel, it is accessible through the small hole on the left side, closest to the rear and may
be adjusted by inserting a small, flat-headed screwdriver.
6. The Tone control sets the desired sidetone pitch from approximately 300 to 1200 Hz. Turn the
control clockwise to raise the pitch and counter-clockwise to lower the pitch. This control is lo-
cated internally. When looking at the unit's front panel, it is accessible through the small hole
on the left side, closest to the front and may be adjusted by inserting a small, flat-headed
screwdriver.
7. The Volume control adjusts the sidetone level of the internal speaker. Turn the control clock-
wise to increase the volume and counter-clockwise to decrease the volume.
8. The Direct/Grid-Block Output keying circuit allows keying of grid-block and solid state
transmitters. The MFJ-441 can only key one type of transmitter at a time. This is an internal
jumper selected option. The unit is factory set to direct keying. To change to grid-block keying
the power must be off, then remove the cover by removing the two screws (one on each side)
that secure it. Locate JMP 1 and JMP 2. JMP 2 is directly behind the RCA jack and JMP 1 is ap-
proximately one inch in front of JMP 2. Set both jumpers JMP 1 and JMP 2 to the "G" position.
