MFJ-269 Instruction Manual HF/VHF/UHF SWR Analyzer
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2.) Coaxial lines can lay in a pile or coil on the floor. Internal or external power can be used, and the MFJ-269
can be placed on or near large metallic objects with no ill effects. Coaxial lines connect normally, with the shield
grounded.
When tuning critical stubs,
gradually
trim the stub to frequency. Adjust the feedline or stub using the following
method:.
1.
Determine the desired frequency and theoretical length of the feedline or stub.
2.
Cut the stub 20 percent longer than calculated.
3a.
Measure frequency of lowest resistance and reactance, or lowest impedance for odd quarter wave stubs. For
fine tuning look only at the “X=?” display. Adjust for X=0, or as close as X=0 as possible. The frequency
should be about 20% below the desired frequency if everything worked as planned during the length
calculation.
3b.
For 1/2 wavelength stubs, measure the frequency of highest Zo where the analyzer overflows and Z>1500
appears.
4.
Divide the measured frequency by the desired frequency.
5.
Multiply the result by the length of the feedline or stub to find the required length.
6.
Cut the stub to the length calculated in step 5, and confirm lowest “X” is on he desired frequency.
The Distance to Fault mode can also be used. It will directly display the line length in degrees at any frequency
you choose. See section
5.5 Advanced 2
.
7.2 Velocity Factor of Transmission Lines
The MFJ-269 accurately determines velocity factor of any transmission line. Select the
Distance to Fault
mode
in
5.5 Advanced 2
.
1.) If a balanced line is used, operate the MFJ-269
only
from internal batteries. Keep the MFJ-269 a few feet
away from other conductors or earth, and do not attach any wires (other than the stub) to the unit. Use the
ANTENNA connector’s shield for one lead and its center pin for the other. Two wire balanced lines
must
be
suspended in a straight line a few feet away from metallic objects or ground.
2.) Coaxial lines can lay in a pile or coil on the floor. Internal or external power can be used, and the MFJ-269
can be placed on or near large metallic objects with no ill effects. Coaxial lines connect normally, with the shield
grounded.
The Distance to Fault mode measures the
electrical length
of a transmission line if a Vf of 1 is entered. To obtain
velocity factor, you must know the electrical and physical length of the line. If the length in feet displayed (with a
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