MFJ-441 Instruction Manual
SlimLine Econo Keyer
2
To key a solid state transmitter, set both jumpers to the "D" position.
Note: Power must be off when changing the jumper settings.
9. The Iambic Type A/B mode is also set inside the unit with a jumper. The unit is factory set
for Type "A" Iambic. If you prefer Type "B" Iambic, remove the cover by removing the two
screws (one on each side) that secure it. Locate jumper JMP 3 and set it to the "B" position.
For Type "A" Iambic, set the jumper to the "A" position.
Note: Power must be off when changing the jumper settings.
When a squeeze is released during an element (dot or dash), type "B" adds the opposite ele-
ment. Type "A" just finishes the element in progress and does not produce a following alter-
nate element. For example, in Type "A" Iambic, a squeeze release during the "dah" in the letter
A will produce "di-dah" (A). In Type "B" Iambic, a squeeze release during the "dah" in the let-
ter A will produce "di-dah-dit" (R).
Installation
1. A 9-Volt battery (not included) may be installed. Remove the cover by removing the two
screws (one on each side) that secure it. A battery holder, located inside the enclosure, is pro-
vided for installing a 9-volt battery.
2. A 12 VDC power supply may also be used to power the MFJ-441. A 2.1 mm coaxial plug with a
positive center and a negative sleeve should be used to power this unit. The MFJ-1312B, an
optional 12 volts adapter, is available from MFJ Enterprises, Inc. The battery is automatically
disconnected when external power is used.
3. A squeeze or single lever key can be used. Squeeze key allows Iambic operation. A 1/4-inch
stereo phono plug and a two-conductor shielded cable should be used. If separate shielded ca-
bles are used, the two shields should be tied together and connected to ground. The dot wire
should be connected to the tip of the plug and the dash wire to the ring. The MFJ-441 be-
comes a manual keyer when a straight key is used. The unit will safely key your transmitter
and eliminate the shock hazard of high voltage being present on the straight key.
Note: To use a straight key, first switch the keyer to the Semi-Auto mode (button in). Again a
1/4-inch stereo phono plug should be used because a mono plug will not work on a straight
key in Semi-Auto mode. Connect one wire to the ring of the plug and another wire to ground.
The tip of the plug should not used.
4. Output keying circuit allows keying of grid-block and solid state transmitters. Remember this is
internally jumper selected (refer to page 2). The keying output connection is made with a RCA
phono plug.
Note: Consult the transmitter's instruction manual to determine which output to use. When in
doubt, try both jumper positions. The transmitter will key continuously when the jumpers are
connected to the wrong positions.
