MFJ-989D VersaTuner V
Instruction Manual
7
Installing the MFJ-989D
T
he block diagram below shows a typical tuner installation.
Station
Ground
Gnd
Gnd
Coax-1
Coax-2
Meter
Lamp
Transmitter
Line
Ant #1 Ant #2
+12 vdc
Jumper
Wire
Balanced
Feed
Ant #3
Radio
Tuner
Here are some important installation guidelines:
1.) Tuner Location:
Position the tuner for convenient access to all front panel controls. However, make
sure you cannot make accidental contact with RF-energized open-wire lines or longwire lead-ins
connected to the rear panel (serious RF burns could result).
Also, never operate the tuner with the cover
removed!
2.) Transmitter Patch Cable:
Use a short direct connection between your transmitter and the tuner. The
cable should be good-quality 50-Ohm stock that is rated for the full amount of power you intend to run.
Also, never install a balun between the tuner and transmitter or string ferrite beads on the cable!
3.) Tuner Grounding:
Connect the tuner chassis directly to your station's ground system. Don't rely on
the patch cable to ground the tuner to your radio or amplifier.
4.) Lightning Protection:
Make provisions to disconnect all antennas from your station in the event of
violent weather. Lightning arrestors may reduce damage from nearby strikes, but only disconnection can
reduce the odds of damage from a direct hit.
Important Warnings: Never install the tuner where you could come in contact with exposed open
wire lines connected to the rear panel. Also, never operate with the tuner cover removed. Finally,
always disconnect all antennas at the first sign of electrical storm activity!
As previously noted, the MFJ-989D incorporates five very useful station accessories into a single
package. Here are operating instructions for each one, beginning with the power meter and SWR bridge.
SWR/Wattmeter
The SWR bridge is configured at the
Transmitter
(or input) side of the tuner and it is always in-line with
the transmitter, regardless of the
Antenna Selector
setting. To measure forward and reflected power:
