MFJ-993B IntelliTuner Automatic Antenna Tuner
Instruction Manual
2005-2012 MFJ Enterprises, Inc.
21
Operation
Manual Tuning
Manual tuning may be used to “touch up” the tuner’s settings. For example, if the target SWR is set at
the default of 1.5, the tuner will stop when a match of 1.5 is found. In all cases, manual tuning gives the
user control of the tuner if desired, and the L-Network menu provides a picture of the matching network
configuration. Manual tuning should always be done at low power, and is accomplished by using the [C-
UP], [C-DN], [L-UP], and [L-DN] buttons. Since it is not known if more or less capacitance or
inductance is needed, manual tuning must be by trial-and-error. As an example, to manually tune
capacitance, press [C-UP] one time, and the reflected power will indicate if [C-UP] was the right
“direction.” If it was, press [C-UP] again and observe reflected power. If not, press [C-DN] twice (once
to return to the original setting of C, and once for one click past it).
Manual tuning of inductance is similarly accomplished, using [L-UP] and [L-DN]. Since the capacitance
and inductance are interdependent, some back-and-forth between the two may be needed, just as in a
conventional tuner with knobs.
Pressing [C-UP] and [C-DN] simultaneously moves the capacitance back and forth from one side of the
inductance to the other. The L-Network menu displays the capacitance on the left to indicate that the
capacitance is on the antenna side (corresponding with the rear panel configuration of connectors); the
capacitance value moves to the right side of the display when the capacitance is on the transmitter side of
the inductance. A general rule of thumb is that loads with impedance higher than 50 ohms call for the
capacitance on the antenna side; loads with impedance lower than 50 ohms call for the capacitance on the
transmitter side.
Pressing [C-DN] and [L-DN] simultaneously or pressing [TUNE] quickly places the tuner in bypass
mode; i.e. zero inductance and zero capacitance. RF from the transmitter goes directly to the antenna
with no matching. The reflected needle bounces to 20-watt mark to indicate the bypass mode. Also, the
decimal point in the SWR reading is replaced with a comma.
Pressing [TUNE], [C-DN] and [L-DN] simultaneously (must be pressed within 80ms of each other)
overwrites the tuner memory with the current tuner setting. Settings with SWR greater than 3.0 will not
be stored. Both forward and reflected needles go to full scale to indicate memory overwrite.
Meter Codes and Audible Beeps
In addition to displaying power and SWR, the meter also indicates tuner status. The meter needles
bounce, or rise to one point and stay, to provide information. In this mode the meters do
not
indicate
power levels. For example, when you press [C-DN] and [L-DN] simultaneously to place the tuner in
bypass mode, the reflected needle bounces to the 20 watts mark until you release the buttons. The
following tables show the meter needle stationary and bounce codes.
