MFJ-993BRT 300 Watt IntelliTuner
TM
Automatic Remote Antenna Tuner Instruction Manual
© 2011 MFJ Enterprises, Inc
MFJ-993BRT Version 1A
4
Note: Route all single and random wire antennas safely to prevent RF burn hazard. For balanced
feedlines, connect an MFJ-912 1.5 kW 4:1 balun to the antenna connector output of the MFJ-993BRT.
Note: When the UHF RF output connector is not used, it should be covered so dirt and/or moisture does
not accumulate in the connector. A dirty open connector is susceptible to arcing under severe SWR
conditions.
Figure 2: Side View of Connectors
5. Connect a wire from a MFJ-993BRT GROUND wing nut to an adjacent antenna ground point.
See “Grounding Hints” on page 24. A good ground is important for the best operation of the
antenna and to reduce the chance of RF interfering with the tuner operation and causing the
tuner to go into bypass mode.
6. If a Lightning Surge Suppressor is used in line with the feed line to the tuner make sure it is
the type that will pass DC such as the MFJ-272 as DC power is supplied through the feed
line.
7. Connect a 12-15V power supply to the DC input of the MFJ-4117 BIAS TEE to supply power
to the tuner. The station supply or an MFJ-1316 will work. The supply needs to be capable of
supplying 1.4A. The use of a regulated supply is not mandatory but is recommended for best
performance. An optional 12 volts DC 1.5 amp power supply, the MFJ-1316, is available from
MFJ Enterprises, Inc.
WARNING
:
Applying greater than 18 volts to the MFJ-993BRT can result in permanent damage.
8. If an optional local antenna switch is used place it before the BIAS TEE (the RF side not the
RF/DC side) to prevent the chance of shorting out the DC line with the switch.
Note: The MFJ-993BRT is not designed to be placed AFTER remote antenna switches. Some antennas
and antenna switches have DC continuity between the center pin and shield which will short out the
power supply when switched to those positions
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 turned on, the tuner powers up in bypass mode.