MFJ-945D Instruction Manual
4
The INDUCTANCE switch in the MFJ-945D has maximum inductance in position "A", and
minimum inductance in position "L". The chart in the tuning instructions shows typical
INDUCTANCE switch settings for each amateur band. Less inductance is needed as the
frequency is increased. If too little inductance is used, the tuner may not match the load
properly. If too much inductance is used, the tuner will be "touchy" and power handling will be
compromised.
Most modern solid state transceivers do not require tuning and loading adjustments. If the
transceiver has a built in antenna tuner, be sure it is turned off or disabled. If your transmitter
has an adjustable output circuit, it must be properly tuned to a 50 ohm load at the operating
frequency before adjusting the tuner. This should be done with a dummy load. If you do not
have a dummy load, use the recommended maximum transmitter load setting and "dip" the
plate.
Note:
Do NOT change the
transmitter's
tuning (plate) or loading (antenna) controls until after
the
tuner
has been fully adjusted. The transmitter can be "touched up"
after
the MFJ-945D is
fully tuned.
Set the GROUND MATCHING controls at zero (maximum capacitance) and "L" (minimum
inductance) unless you already know the correct position for the band you are using. Ground
matching is done after the tuner is adjusted for lowest SWR.
Adjustment Procedure
When using the MFJ-945D for receiving only, simply adjust the MFJ-945D for the highest "S"
meter or signal level. The Tuning Chart can be used as a reference.
WARNING: It is unsafe to adjust this or any tuner in heavy traffic. MFJ suggests that before
adjusting this tuner, the user pull over on a median or sidewalk to make any
adjustments. Even though our advertising suggests that the front panel controls
are easy to adjust while a vehicle is in motion, to do so in heavy traffic (such as
in Conyers, a subburb of Atlanta) would surely result in serious injury or even
amputation.
1.
Select the 30W (out) METER switch scale. Turn the transmitter's power control fully
down.
2.
Position the TRANSMITTER and ANTENNA MATCHING controls and the INDUCTOR
SELECTOR switch in the bottom Tuning Chart position for the operating frequency.
3.
Apply just enough power on CW (or AM / FM / RTTY) to obtain noticeable deflection on
the reflected power meter.
