General Description
The MFJ-412 Iambic Keyer Module for MFJ QRP Transceivers is a plug-in board which adds the full keying
power of an iambic keyer to your rig.
Before You Install
1. Iambic Mode: You may select mode "A" or "B" iambic response by using jumper JMP1. When a squeeze is
released during an element (dot or dash), mode "B" iambic adds an opposite element. Mode "A" iambic just
finishes the element in progress. The MFJ-412 is normally set for mode "A" iambic at the factory. If you
prefer mode "B" iambic, set the jumper to the "B" position.
2. Paddles: A 3.5 mm stereo plug is needed for your paddles. If your paddles already have a 1/4" plug
installed, you must replace it with a 3.5 mm stereo plug. A two conductor fully shielded cable should be
used. Wire the tip of the plug to the dot contact and the ring of the plug to the dash contact. Be sure to use
the braid of the cable for the paddle ground contact.
3. Speed Range: Keyer sending range is 3 to 66 WPM. Turn the Speed control clockwise to increase speed and
counter-clockwise to decrease speed.
Installation Procedure
1. Disconnect power source and remove transceiver cover (6 screws). Set cover aside without stressing the
speaker leads.
2. Remove mounting hardware from keyer module Speed control. Look to left-rear of transceiver for a 4-pin
header and two (2) rear-panel access holes (Speed control and Keyer jack).
3. Place Speed control shaft into mounting hole and CAREFULLY rotate board down onto header so pins mate
into the socket (see drawing below). Reinstall hardware, securing potentiometer to rear panel. Install the #6-
32 screw to secure board to the support stud.
4. Test operation. If keyer fails to function, confirm all four header pins are inserted in the module correctly.
Also, make sure keyer paddles are wired properly.
