MFJ MFJ-213 - Measuring Unknown Capacitance; Measuring Unknown Inductance; Determining Cable Velocity Factor

MFJ-213 HF/VHF/UHF Antenna Analyzer Instruction Manual
7.2 Measuring Unknown Capacitance
To measure capacitance, connect the unknown component to the Antenna
connector (usable range is from approximately 15 pF to 1200 pF). To enter
the Capacitance mode, begin with the analyzer at the main menu and select
the LC-meter function (see Section 3.1.3). The screen will display the
approximate value of the unknown capacitor in pF along with the stimulus
frequency where the measurement is being made. The best accuracy is
typically obtained in the 4 to 9 MHz range, which may be selected using the
BAND button and the TUNE knob. Note that any capacitor and lead
combination that approaches self-resonance at the stimulus frequency will
trigger the C = Xc >1.5KQ message and will be un-measurable. Attempt to
re-measure at a lower frequency.
7.3 Measuring Unknown Inductance
To measure inductance, connect the unknown component to the Antenna
connector. To enter the Inductance mode, begin with the analyzer at the
main menu and select the LC-meter function then press the MODE button
to select the inductance mode(see Section 3.1.3).The screen will display the
approximate value of the unknown inductor in uH along with the stimulus
frequency where the measurement is being made. The best accuracy is
typically obtained in the 2 to 9 MHz range, which may be selected using the
BAND button and the TUNE knob. Note that any inductor approaching self-
resonance at the stimulus frequency will trigger the L = X, >1.5KQ message
and will be un-measurable. Try to re-measure at a lower frequency.
7.4 Determining Cable Velocity Factor
If you have coax cable with an unknown velocity factor, you can determine
it quickly using the following procedure:
(1.) Set the MFJ-213 up in Analyzer mode (Section-3)
(2.) Set the frequency to around 20 MHz (Section-4)
(3.) Make a 1/4-A stub from 9 feet of the unknown cable and connect it to the
analyzer (other end open)
(4.) Rotate Tune for minimum impedance magnitude reading. Write down
the frequency (in MHz)
(5.) Divide 246 by this frequency to find the free-space 1/4-A wavelength in
feet (L = 246 +f MHz)
(6.) Divide 9 (the actual length) by free-space 1/4- wavelength to get the
Velocity Factor (VF =9 +L)
Note that there is nothing magical about the 9-foot stub length, other than it
falls conveniently within the limits the tuning range. Other lengths could be
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