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MFJ-991 / MFJ-994 IntelliTuner Automatic Antenna Tuners
Fast Start
● Never operate the tuner with its cover removed. Contact with the components inside the
tuner while transmitting will result in painful RF burns.
● Locate the tuner so that the rear terminals are not accessible during operation. The single
wire connection may have high voltage while transmitting.
● Disconnect all antennas from the tuner during lightning storms.
● Always tune with low power (about 10 watts). Apply maximum power only after tuning up.
● Never exceed tuner specifications.
● Do not transmit with a high SWR for extended periods of time.
1. Connect the tuner to a 12-15 VDC voltage source capable of supplying at least 1 amp.
2. Connect your transmitter to the TRANSMITTER connector using a 50-ohm coaxial cable.
3. Connect your coax-fed antenna to the ANTENNA connector using a 50-ohm coaxial cable, or
connect your random wire to the WIRE binding post.
4. Press the [POWER] button to turn on the tuner. Lock the [AUTO] button in to select semi-automatic
mode.
5. Key your transmitter to output a carrier of 10 watts CW, FM or AM.
6. Press the [TUNE] button briefly to start the automatic tuning process. When completed, check to
ensure an SWR of 2.0 or less before increasing RF power.
7. You are ready to transmit.
Note: During the automatic 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.
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 the tuner power is ON, pressing [C-DN] and
[L-DN] simultaneously places the tuner in bypass mode (zero inductance and zero
capacitance) and indicates by the reflected needle bouncing to 20 watts.
Transmitter
© 2004 MFJ Enterprises, Inc.
WARNINGS
50-ohm Coax
RF Ground
Figure 1. Installation Block Diagram.
Automatic
Tuner
12 VDC
Instruction Manual
Antenna
3
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