MFJ-209 SWR Analyzer Instruction Manual
12
MEASURING INDUCTANCE AND CAPACITANCE
To measure capacitance or inductance you will need some standard value capacitors and
inductors. These should be collected and tested for accuracy. MFJ suggests the following sets
of values:
Inductors: 330µH, 56 µH, 5.6 µH, 0.47 µH
Capacitors: 10 pF, 150 pF, 1000 pF, 3300 pF
Readings will be the most accurate if the standard test values used are between 0.5 µH to 500
µH to measure capacitance or 10 pF and 5000 pF to measure inductance.
Take a component of unknown value and connect it in series with a standard component to
make a series LC circuit. Attach the series LC circuit to the "ANTENNA" connector in series
with a 50 Ω resistor.
Measure capacitance.
1. Connect an unknown capacitor in parallel with the highest value standard inductor.
2. Connect the LC circuit to ANTENNA connector with a 50 Ω resistor in series.
3. Adjust the tune knob through the bands until you get the lowest SWR. If you do not get a
deep meter deflection change to the next inductor with a lower value and try again.
Continue the process until you obtain low SWR. Read the resonant frequency off the MFJ-
209 scale or measure it with a counter.
4. Solve this equation using F as the resonant frequency as L as the inductance of the standard
inductor,
C(pF) =
00003948F L
F = MHz L = H
2
.
µ
Measure inductance.
1. Connect an unknown inductor with the highest value standard capacitor in parallel.
2. Connect the LC circuit to "ANTENNA" connector with a 50 Ω resistor in series.
3. Adjust the tune knob through the bands until you get the lowest SWR. If you do not get a
deep meter deflection change to the next smaller value standard capacitor and try again.
Repeat the process until you get low SWR.
4. Solve this equation using F as the resonant frequency and C as the capacitance of the
standard capacitor.
L( H) =
00003948F C
F = MHz C = pF
2
µ
.
RESONANT FREQUENCY OF TUNED CIRCUITS
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