Care Use and Feeding
of a
MFJ-259B Antenna Analyzer
MFJ-259B Description
Schematic
Block Diagram
Vz= Voltage across the load.
Vr= Voltage indicating bridge balance.
Vs= Voltage across a series 50-ohm resistor
between the RF source and the load.
MFJ-259B Operation
Origin - Designed by Tom Rauch - W8JI
www.w8ji.com
Power - External source
Alkaline Batteries
Rechargeable Batteries
Load -
Antenna Connections
Frequency Source
Other Loads
Care and Feeding - Don’t drop it.
Don’t get it wet
Don’t let it bake in the sun.
Be careful of the detector diodes.
Modes of Operation
Main mode 1 - Impedance R & X
14.250 MHz
R= 54
1.1
X= 6 SWR
Impedance R&X is the initial power-up mode. In this mode, the MFJ-259B
LCD (liquid crystal display) shows frequency in MHz, SWR, the resistive
part of load impedance (R=), and the reactive part of load impedance (X=).
The IMPEDANCE meter displays the complex impedance (Z in ohms), and
the SWR meter displays SWR.
Modes of Operation
Main mode 2 - Coax Loss
14.250 MHz
Coax Loss = 12dB
The liquid crystal display(LCD) indicates the test frequency and approximate loss of any 50
ohm coaxial cable, 50 ohm attenuator pad, or 50 ohm transformer or balun (for differential
mode current only). In this mode, the 50 ohm device or cable under test must not be connected
or terminated by a load resistance at the far end.
Main mode 3 - Capacitance
66.120 MHz
263
C=
Xc
9pF
The LCD shows measurement frequency, capacitive reactance (Xc=) in ohms, capacitance
(C=) in picofarads or pF. The Impedance meter indicates reactance in ohms, and the SWR
meter displays SWR.
Modes of Operation
Main mode 4 - Inductance
66.120 MHz
263
L= 0.633μH
XL
The digital display indicates measurement frequency, capacitive reactance (Xl=) in ohms,
inductance (L=) in microhenries or μH. The Impedance meter indicates reactance in ohms, the
SWR meter displays SWR.
Main mode 5 - Freq. Counter
66.12 MHz
0.01s
Freq. Counter
The BNC connector labeled FREQUENCY COUNTER INPUT should connect to the RF
sample you want to measure. The sensitivity of this port rangesfrom 10 millivolts at 1.7 MHz
to 100 millivolts at 180 MHz. The frequency counter is not design for use below 1 MHz. The
“GATE” button controls the gate time of the frequency counter. (.01, .1 or 1 second)
Modes of Operation
Advanced Modes - Press and hold both the “Gate” and “Mode” buttons
simultaneously until the display shows “Advanced” and then release.
Advanced
Advanced mode 1 - Impedance
12.004 MHz
Z= 49
1.0
θ= 0º SWR
In this mode, the MFJ-259B LCD displays frequency, impedance or Z magnitude (in
ohms), and phase angle ( θ ) of impedance. The meters indicate SWR and Impedance.
The maximum impedance limit is set at 650 ohms, indicated by the standard display of
(Z>650).
Modes of Operation
Advanced mode 2 - Return Loss
& Reflection Coeff.
12.120 MHz
>25
RL=0.3dB ρ=.96 SWR
The Return Loss and Reflection Coefficient mode measures and displays return loss in dB and
voltage reflection coefficient in percent on the LCD. The meters indicate SWR and impedance.
Advanced mode 3 - Distance to
Fault
8.3153 MHz
DTF
1st
X= 0
Select a frequency where the Impedance meter is at the lowest deflection possible and where
minimum reactance displayed on the MFJ-259B LCD.
Press the “GATE” button. The blinking “1st” on the display will change to “2nd”.
Modes of Operation
Distance to Fault continued
25.047 MHz
DTF
2nd
X= 0
Tune the frequency control to the very next dip in impedance and lowest reactance.
Press the “GATE” button again.
Dist. To Fault
29.1 ft. x Vf
The LCD display will now show the electrical distance to the fault. To convert that to a
physical distance, multiply that number by the velocity factor of the cable.
If in this example RG-8 coax was used the velocity factor is .66, so the actual distance would
be 19.2 ft.
Modes of Operation
Advanced mode 4 - Resonance
Mode
12.120 MHz
1.0
R= 49 [X= 0] SWR
The Resonance Mode displays reactance on the IMPEDANCE meter. In this mode, the MFJ259B measures frequency, SWR, resistance (R= ), and reactance (X= ). When reactance is zero,
the system is said to be resonant.
Advanced mode 5 - Match
Efficiency
(Percent Transmitted Power)
25.167 MHz
4.0
Match = 64%
SWR
Percentage of transmitted power is yet another way of describing SWR. It is similar to
mismatch loss, but SWR data is expressed as a “percentage of transmitted power”.
Measuring an Antenna