MFJ-994B IntelliTuner Automatic Antenna Tuner Instruction Manual
© 2004-2010 MFJ Enterprises, Inc.
4
Note: When the tuner power is OFF, the tuner is bypassed and RF from the transmitter or
amplifier goes directly to the antenna with no matching. The MFJ-994B always powers
up in bypass mode to ensure maximum receiver sensitivity if you are listening on a
different frequency than where tuning last occurred. When tuning starts, the MFJ-994B
reverts to previously stored matching values or finds a new match if no previous
information is in memory. You may bypass the tuner at anytime when the tuner power is
ON by pressing [C-DN] and [L-DN] simultaneously or pressing [TUNE] quickly. When
the MFJ-994B is bypassed, the reflected meter needle bounces to the 20-watt mark while
the switches are pressed.
Figure 1. Typical Installation Block Diagram.
Front Panel
MODEL
MFJ-994B
C-UP L-UP AUTO POWER
C-DN
L-DN
TUNE
AUTOMATIC ANTENNA TUNER
600 Watts SSB / CW
MFJ IntelliTuner
TM
0
1
0
3
0
5
0
1
0
0
2
0
0
3
0
0
0
5
2
0
4
0
6
0
8
5
.
0
3.0
2.0
1
.
5
1
.
2
Hi x1
Lo x.1
400-3 083
1
1
0
BYPASS
Z
Figure 2. MFJ-994B Front Panel.
• SWR/Wattmeter: The cross-needle meter measures forward power, reflected power, and SWR. It
operates whenever the MFJ-994B is powered on. The default full-scale readings are 3000 watts
forward and 600 watts reflected power. The meter can be set to a low power range of 300 watts
forward and 60 watts reflected, or AUTO metering where the meter range is determined by the
transmit power. The SWR is measured at the point where the two needles cross. See
“SWR/Wattmeter” on page 11 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 2950 pF. The upper limit of capacitance, dependent
on frequency, is restricted to limit the maximum voltage and current across the tuner’s components.
HF Transceiver
Ameritron
ALS-600 HF
Power Am
lifie
MFJ-994B
Automatic
Antenna Tuner
Radio Interface Cable
Antenna
Single Point Ground
Ameritron ARB-704
Amplifier Interface
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