MFJ MFJ-993, Instruction Manual

MFJ-993 IntelliTuner Automatic Antenna Tuner 

Instruction Manual 

©

 2003-2004 MFJ Enterprises, Inc. 

5

• 

L-UP and L-DN Buttons:

  Used to manually increase or decrease the inductance of the L-network 

matching circuit.  The inductance range is 0 to 24.86 µH (microhenries).  The upper limit of 
inductance, dependent on frequency, is used to limit the maximum voltage and current across the 
tuner’s components.  This limit can be removed in the LC Limit setup menu, but is not recommended. 

Shortcut: 

Press both [L-UP] and [L-DN] buttons simultaneously to toggle SWR Beep on and 
off.  See “SWR Beep Menu” on page 15. 

Note: 

Pressing [C-DN] and [L-DN] (both DOWN buttons) simultaneously places the tuner in 
bypass mode.  The reflected needle bouncing to the 20-watt mark indicates this.  RF from 
the transmitter goes directly to the antenna with no matching. 

• 

AUTO Button:

  Used to select automatic or semi-automatic tuning mode.  Button 

out

 selects 

automatic mode--the tuning routine is automatically started when at least 5 watts of power is applied 
and the SWR is a preset amount above the preset target SWR.  Button 

in

 selects the semi-automatic 

mode--the tuning routine starts only when the [TUNE] button is pressed.  The Auto/Semi indicator on 
the main display indicates the selected mode. 

Note: 

During the tuning process, the tuner will make some noise.  These are the relays 
switching at a very fast pace and it is normal operation.  Do not be alarmed. 

• 

TUNE Button:

  Has three different functions based on the length of time you press and hold it before 

releasing.  Press [TUNE] quickly (less than 0.5 second) to bypass the tuner.  RF from the transmitter 
goes directly to the antenna with no matching. 

Press and hold [TUNE] for 0.5 to 2 seconds to start the automatic tuning process.  The transmitter 
must be keyed first with at least 5 watts of power.  When the SWR is already below the target SWR, 
pressing [TUNE] will fine-tune the match for a lower SWR, if possible. 

“

StickyTune

” allows for one-handed tuning operation.  Normal tuning requires keying the transmitter 

with one hand and using the other hand to push the [TUNE] button to start the tuning process.  To 
toggle the 

StickyTune

 mode on and off, press and hold the [TUNE] button for two seconds.  When 

enabled, a bar appears on top of the Auto/Semi indicator, and the tuning process starts automatically 
when the transmitter is keyed with at least 5 watts of power regardless of the SWR.  This works in 
both automatic and semi-automatic modes.  One beep indicates on and two beeps indicate off. 

• 

VOL Control:  

A trimpot control that adjusts the volume level of the aural SWR meter.  Use a small 

flat blade screwdriver and turn clockwise to increase volume level. 

• 

POWER Button:

  Used to turn the power on and off.  Note that during power-on the analog meter 

bounces three times (to indicate the model number, 99

3

).  When the power is off, the tuner is placed 

in bypass mode and Antenna 1 is selected.  When turning on the power, the tuner automatically 
restores all previous settings and displays the target SWR on the main screen. 
 

WARNING: 

Do not turn the power on and off rapidly, otherwise the tuning setting 
memory can be corrupted and the unit will have to be reset to factory defaults. 

Note: 

When the tuner power is OFF, the tuner is in bypass mode and RF from the transmitter 
goes directly to the antenna (ANTENNA 1) with no matching.