MFJ-925 Super-Compact IntelliTuner Automatic Antenna Tuner
Instruction Manual
©
2006 MFJ Enterprises, Inc.
3
Fast Start
WARNING
●
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 MFJ-925 to a 12-15 VDC voltage source capable of supplying at least 750 milli-amps.
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 ANTENNA connector through the supplied adaptor.
4. Connect your ground connection to the GROUND post.
5. Press the [POWER] button to turn on the MFJ-925 tuner.
6. Press the [ALT] button momentarily until there is one beep. One beep indicates that memory 1 is
selected.
7. Key your transmitter to output a carrier of 10 watts CW, FM or AM.
8. Press and hold the [TUNE] button on the MFJ-925 for one second to start the automatic tuning
process. When completed, check to ensure an SWR of 2.0 or less before increasing RF power.
9. 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 [TUNE]
quickly places the tuner in bypass mode (zero inductance and zero capacitance) and indicates
by one beep.
Transmitter
MFJ-925
50-ohm Coax
Antenna 1
RF Ground
12 VDC
Figure 1. Installation Block Diagram.
Summary of Contents for MFJ-925
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