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MFJ-991 / MFJ-994 IntelliTuner Automatic Antenna Tuners
Front Panel
3.0 2.0
Hi x1
Lo x.1
400-3083
MODEL
MFJ-991
•
SWR/Wattmeter: The cross-needle meter measures forward power, reflected power, and SWR. It
operates whenever the tuner is power on. Full-scale readings are 300 watts forward and 60 watts
reflected. The meter can be set to low power range of 30 watts forward and 6 watts reflected.
(Double these figures for the MFJ-994). The SWR is measured at the point where the two needles
cross. See "SWR/Wattmeter" on page 8 for more detailed information.
•
C-UP and C-DN Buttons: Used to manually increase or decrease the capacitance of the L-network
matching circuit. The capacitance range is 0 to 3900 pF (0 to 2950 pF in the MFJ-994). The upper
limit of capacitance, dependent on frequency, is restricted to limit the maximum voltage and current
across the tuner's components.
Note: Pressing [C-UP] and [C-DN] simultaneously toggles the capacitor between the input
and output sides of the L-network. Forward needle bounces to 30 watts when the
capacitor is on the transmitter side. Reflected needle bounces to 5 watts when the
capacitor is on the antenna side.
•
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 µH (0 to 17 µH in the MFJ-994). The upper limit
of inductance, dependent on frequency, is restricted to limit the maximum voltage and current across
the tuner's components.
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 (10 watts for MFJ-
994) 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.
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.
4
MFJ IntelliTuner
AUTOMATIC ANTENNA TUNER
150 Watts PEP SSB / 100 Watts CW
Figure 2. Front Panel (MFJ-994 same except for label).
C-UP
L-UP
Z
C-DN
L-DN
TM
BYPASS
300 / 30
WATTS
AUTO RANGE
© 2004 MFJ Enterprises, Inc.
Instruction Manual
AUTO
POWER
TUNE
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