MFJ-259 Instruction Manual
HF/VHF SWR Analyzer
13
A properly designed current balun, the type that is the most effective and usually handles the
most power, should show a low SWR over the entire operating range of the balun with the
clip lead in any of the three positions.
A well designed voltage balun should show a low SWR over the entire operating range when
the clip lead is in position "B". It will show a poor SWR when the clip lead is in position "A"
and "C".
A voltage balun should also be tested by disconnecting the outer connections of the two
resistors and connecting each resistor in parallel. If the balun is operating properly the SWR
will be very low with the resistors connected from either output terminal to ground.
BALUN
"ANTENNA"
To the MFJ-259's
connector
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: 330
µ
H, 56
µ
H, 5.6
µ
H, .47
µ
H
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
µ
H to 500
µ
H 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 series 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.
4.
Solve this equation using F as the resonant frequency as L as the inductance of the
standard inductor,