MFJ-998 Legal Limit IntelliTuner Automatic Antenna Tuner
Instruction Manual
©
2007-2010 MFJ Enterprises, Inc.
21
Note: When exiting the setup mode,
TURN POWER OFF
message will display if the Radio
Interface menu setting has changed. Turn the tuner’s power off, connect the new radio
interface, then on again to re-initialize the radio interface circuitry.
Note: If the wrong interface is selected and the
TURN ON RADIO
message does not go away,
disable the interface by pressing and holding both [TUNE] and [MODE] while turning on
the power. The tuner will respond with two beeps. Then select the correct interface.
Push Tune <0.5s Menu
Selects how the [TUNE] button behaves when it is pressed momentarily. Refer to the “Tune Button”
section on page 7 for more details. Default is TO BYPASS.
LC Limit Menu
The upper limits of inductance (L) and capacitance (C) are factory-limited according to frequency and
maximum power rating; i.e., higher frequencies need less inductance and less capacitance when the L-
network is properly tuned. Pressing [C-UP] and/or [L-UP] allows capacitance and inductance to be
increased only to these limits. When a selected capacitance or inductance is higher than its allowed limit,
and the frequency is changed, that selection is automatically reduced to the value of its limit. These limits
are used to prevent matching of extreme load impedance outside the tuner’s specification, which may
result in excess voltage and/or current across the tuner’s components. This setting is not stored in non-
volatile memory and reverts back to the default when the tuner power is cycled. Refer to Figures 16 and
17 for the on-screen LC Limit indicator. Default is ON.
Note: If this feature is turned OFF, it will be re-set to ON whenever power is cycled.
WARNING: LC Limit is a safety precaution; the tuner is in danger of being damaged if this
function is turned off.
Operation
Manual Tuning
Note: Manual tuning must only be attempted under low power (less than 20 watts) conditions.
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).
