MFJ-998RT Legal Limit IntelliTuner
TM
Automatic Remote Antenna Tuner Instruction Manual
© 2011 MFJ Enterprises, Inc
MFJ-998RT Version 1A
7
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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. One beep
indicates bypass mode, where RF from the transmitter goes directly to the antenna with no
matching. A second quick press toggles the tuner back to its last L/C setting, and the tuner
responds with two beeps.
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Press [TUNE] for 0.5 to 2 seconds to start the automatic tuning process. Tuning starts when
[TUNE] is released after the 0.5-2 second hold-time. The transmitter must be keyed first with at
least five 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.
Note: You can reverse the two functions above by pressing and holding the [TUNE] button for
approximately 10 seconds. I.e., when the [TUNE] button is pressed and held for 10 seconds. You will
hear two beeps. Now pressing [TUNE] momentarily starts the tuning process, and pressing and holding
the [TUNE] button for 0.5-2 seconds puts the tuner into the bypass mode.
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Automatic/Semi-Automatic Tuning Mode
Automatic Tune mode is the standard mode for the MFJ-998RT.
Pressing [TUNE] and [ANT] simultaneously toggles between automatic and semi-automatic
tuning mode. In automatic mode, the tuning routine is automatically started when at least five
watts of power is applied and the SWR is a preset amount above the preset target SWR. In semi-
automatic mode, the tuning routine starts only when the [TUNE] button is pressed for 0.5 to 2
seconds. The Auto/Semi indicator on the main display indicates the selected mode. Refer to
Figures 15 and 16 for the on-screen Auto/Semi indicator.
Note: During the tuning process, the tuner will make some noise. These are the relays switching at a very
high rate, and it is normal. Do not be alarmed.
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POWER Button: Used to turn the power on and off. The MFJ-998RT should normally be left in the
ON position and switched remotely. When the power is off, the tuner is placed in bypass mode,
When turning on the power, the tuner powers up in the bypass mode and displays the target
SWR on the main screen.
Note: When remotely switching the power off and on leave the power off for at least 2 seconds so the
power supply capacitors in the tuner completely discharge.
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The tuner requires 12 volts DC at up to 1.4 amps. The use of a regulated supply is not mandatory
but is recommended for best performance. An optional 12 volts DC 1.5 amp power supply, the
MFJ-1316, is available from MFJ Enterprises, Inc.
WARNING
:
Do not apply voltages greater than 18 volts to this unit, or permanent damage to the unit may result.
Note: When the tuner power is OFF, the tuner is in bypass mode and RF from the transmitter goes
directly to the antenna with no matching. When turned on, the tuner powers up in bypass mode.
