MFJ-993B IntelliTuner Automatic Antenna Tuner
Instruction Manual
2005-2012 MFJ Enterprises, Inc.
18
Auto Tune SWR Menu
Allows you to set the SWR threshold
in the range 0.5 to 1.5. In the automatic mode, the tuning process
will automatically start when the SWR is above the target SWR by this amount of SWR threshold. For
example, for target SWR of 1.5 and auto tune SWR of 0.5, the tuning process will start whenever the
SWR rises above 2.0 (1.5 + 0.5) and there is at least two watts of RF power applied. Default is 0.5.
Shortcut:
Press both [TUNE] and [L-UP] buttons simultaneously to cycle the auto tune SWR
among 0.5, 1.0 and 1.5. Refer to Table 2 for meter code.
Note:
The AUTO button should always be IN (semi-automatic) unless a compatible radio interface
cable is connected between the MFJ-993B and your transceiver. This will ensure that the
MFJ-993B does not attempt tuning during high-power operation. This is particularly
important when a HF amplifier is also being used.
Note:
If an amplifier is in-line, it should always be bypassed prior to tuning.
Meter Range Menu
Allows you to select the meter scale range. In the 30 watts (low) range, forward full scale is 30 watts and
the reflected full scale is 6 watts (divide the meter reading by 10). In the 300 watts (high) range, the
forward full scale is 300 watts and the reflected full scale is 60 watts. Auto range automatically sets the
meter scales according to the input RF power to the tuner. Forward power greater than 30 watts or
reflected power greater than six watts automatically sets the meter to the high power range. Forward
power less than 25 watts and reflected power less than four watts automatically set the meter to the low
power range. Refer to Figures 13 and 14 for the on-screen Meter Range indicators. Default is the 300-
watt range.
Shortcut:
Press both [TUNE] and [L-DN] buttons simultaneously to cycle the meter range among
30 watts, 300 watts and auto range. Refer to Table 2 for meter code.
Peak Hold Menu
When the peak hold function is ON, the highest activated segment of the forward bar meter remains
visible for about one second, so that you can more easily read it. When OFF, the meter functions
normally. Default is ON.
Memory Menu
Turns the antenna memory on and off. The “memory resolution” is the width of frequency spectrum that
the tuner recognizes as being the same as a tuned frequency already in memory. The memory resolution
is approximately 0.1 percent of the lower frequency of each amateur band. For example, the memory
resolution on the 40-meter band (7000 to 7300 kHz) is 7 kHz; if the tuner has memorized a setting for
7050 kHz, it will automatically call up this setting for any frequency from 7047 to 7053 kHz. Memory
resolution is smaller at lower frequency to accommodate the higher antenna Q and larger at higher
frequency where the antenna Q is lower. The memory resolutions for the HF amateur bands are:
