Care Use and Feedingof 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 - W8JIwww.w8ji.com

Power - External sourceAlkaline BatteriesRechargeable Batteries

Load - Antenna ConnectionsFrequency SourceOther 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

14.250 MHz 1.1

R= 54 X= 6 SWR

Main mode 1 - Impedance R & X

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

14.250 MHz

Coax Loss = 12dB

Main mode 2 - Coax Loss

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.

66.120 MHz 263

C= 9pF Xc

Main mode 3 - Capacitance

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 SWRmeter displays SWR.

Modes of Operation

66.120 MHz 263

L= 0.633μH XL

Main mode 4 - Inductance

The digital display indicates measurement frequency, capacitive reactance (Xl=) in ohms, inductance (L=) in microhenries or μH. The Impedance meter indicates reactance in ohms, theSWR meter displays SWR.

66.12 MHz 0.01s

Freq. Counter

Main mode 5 - 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

Advanced Modes - Press and hold both the “Gate” and “Mode” buttons simultaneously until the display shows “Advanced” and then release.

12.004 MHz 1.0

Z= 49 θ= 0º SWR

Advanced mode 1 - Impedance

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

12.120 MHz >25

RL=0.3dB ρ=.96 SWR

Advanced mode 2 - Return Loss & Reflection Coeff.

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.

8.3153 MHz 1st

DTF X= 0

Advanced mode 3 - Distance to Fault

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”.

25.047 MHz 2nd

DTF X= 0

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

Distance to Fault continued

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

Modes of Operation

12.120 MHz 1.0

R= 49 [X= 0] SWR

Advanced mode 4 - Resonance Mode

The Resonance Mode displays reactance on the IMPEDANCE meter. In this mode, the MFJ-259B measures frequency, SWR, resistance (R= ), and reactance (X= ). When reactance is zero, the system is said to be resonant.

25.167 MHz 4.0

Match = 64% SWR

Advanced mode 5 - Match Efficiency (Percent Transmitted Power)

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