MFJ MFJ-225 Instructions

MFJ ENTERPRISES, INC.

300 Industrial Park Road

Starkville, MS 39759 USA

Tel: [phone] Fax: [phone]

MFJ Graphical

COPY RIGHT 2 013 MFJ E NTERPR ISES , IN C.

Antenna Analyzer

Model MFJ-225

INSTRUCTION MANUAL

CAUTION: Read All Instructions Before Operating Equipment !

VERSION 1B

Table of Contents

1.0: Introduction to the MFJ-225 Analyzer 1

1.1 Manual Information: 1

1.2 General Features: 1

1.3 Panel and Control Layout: 2

1.4 Operating Modes: 2

ANT-G Mode: 3
Cable Mode: 3
ANT-S Mode: 3
PC>USB Mode: 3

2.0 Powering Your Analyzer 3

2.1 Power Sources: 3

2.2 Power Switches: 3

2.3 Battery Selection: 4

2.4 Installing Batteries: 4

2.5 Battery Chargers: 5

2.6 Initial Battery Charge: 5

2.7 Long-Term Storage: 5

2.8 Powering Via a USB Cable: 5

3.0 About DDS Frequency Control 6

3.1 Tune Encoder Functions: 6

[ ] Frequency (F): 6

3.2 Rounding Off: 6

4.0 ANT-G Mode 6

4.1 Accessing Ant-G: 6

4.2 ANT-G Screen: 7

Top Screen 7
Middle Screen 7
Bottom Screen 7

4.3 Test-Signal Generation 7

5.0 Cable Mode 8

5.1 Accessing Cable Mode: 8

5.2 Resonance, Length, and Velocity Factor: 8

5.3 Cable Loss: 9

6.0 ANT- S Mode 10

6.1 Accessing ANT-S Mode: 10

6.2 Frequency Setup for Graphic Displays: 10

6.3 Graph Parameters and their Ranges: 10

7.0 USB>PC Mode 11

7.1 PC Interface: 11

7.2 Accessing USB>PC: 11

7.3 Port Assignments: 11

OUTPUT: 11
INPUT: 11

7.4 IG-miniVNA Freeware: 11

8.0 Measurement Accuracy and Limitations 11

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MFJ-225 Graphical Antenna Analyzer

ii

8.1 General: 11

8.2 Local Interference: 12

8.3 Coupler Loss and Directivity: 12

8.4 Calibration Plane Error: 12

8.5 Sign Ambiguity (±j): 12

8.6 Calibration: 12

9.0 Quick Guide to Controls and Functions 13
External Power: 13
Battery Charger: 13
Turn on Analyzer: 13
ANT-G Test Mode: 13
CABLE Mode: 13
ANT-S Mode: 14
USB>PC Mode: 14

TECHNICAL ASSISTANCE 14
12 MONTH LIMITED WARRANTY 15

MFJ-225 Graphical Antenna Analyzer

1.0: Introduction to the MFJ-225 Analyzer

1.1 Manual Information: The MFJ-225 HF/VHF RF-Analyzer delivers all the

popular measurement functions you've come to expect, plus it takes RF testing to
a new level. Advanced features include full-screen LCD graphics, two-port VNA
measurements, precise DDS frequency control, and direct PC interface running
powerful IG-miniVNA freeware. These features are advanced, but actually less
complicated to use because they reduce the number of steps needed to capture
and view a wide range of data.

Before powering up your MFJ-225 for the first time, please read the manual,
paying special attention to Section-2.0, Powering Your Analyzer. It contains
essential information for installing batteries and supplying power correctly. In fact,
the more you know about the MFJ-225 ahead of time, the sooner you'll be able to
utilize all of its functions and features. Note that a "Quick Guide" reference is
available in Section-9 to recap and help you review the essentials for operating
your unit.

Important Warning: Read "2.0 - Powering Your Analyzer" before loading
batteries or turning it on for the first time. Applying the wrong voltage,
reversing polarity, or loading batteries incorrectly could permanently
damage the unit.

1.2 General Features: The MFJ-225 is really two analyzers in one. By itself, it's

a compact and completely self-contained handheld unit with a rechargeable
battery pack and a back-lit 3-inch 128 x 64 dot-matrix LCD screen to display
graphs and data. Using the Output port, you'll measure a wide range of reflection
(S11) parameters including:

[ ] SWR (1:1 to 9.9:1)
[ ] Complex Impedance (R and X)
[ ] Impedance Magnitude (Z)
[ ] Return Loss (RL, 0 to -25 dB)
[ ] Phase (0-180°)
[ ] Capacitance (0-9999 pF)
[ ] Inductance (.1uH-80 uH)
[ ] Cable Length (0.5-45 m)
[ ] Cable Loss (0-30dB)

Note that important data points like SWR, Impedance Magnitude, Resistance,
Reactance, Return loss, Capacitance, and Inductance are displayed on the
screen simultaneously, eliminating the need to search for them in sub-menus.
You'll also get frequency-swept plots for SWR, Impedance Magnitude, Return
Loss, Resistance, Reactance, and Phase Angle with full control over center
frequency, tuning step, and scan width while viewing the plot.

When paired up with a pc, the MFJ-225 becomes a two-port desktop analyzer
capable of compiling and plotting S11 and S21 measurements. Download IG­miniVNA freeware to your PC from the web at no cost, then connect the analyzer

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MFJ-225 Graphical Antenna Analyzer

Charge LED

using a Type-B USB interface cable. The USB cable carries both power and
data. In no time you'll be measuring all the standard reflected power parameters
(S11) plus forward-power transmission parameters (S21) such as gain, loss,
pass-band slopes, and phase shift. Best of all, your pc captures these
measurements, processes them, and presents stunning color-graphic plots you
can print, store, or transmit electronically to document your work.

Unlike most low-cost analyzers, the MFJ-225 uses DDS (direct-digital synthesis)
for signal generation. It covers the 1.0-MHz to 180-MHz tuning range (HF and
VHF) without breaks or gaps. The constant-amplitude RF signal is virtually free of
harmonics and spurious signals, a big advantage for delivering accurate results.
In addition, you can connect to the OUTPUT port and use the DDS generator as
a independent RF source for driving mixers and amplifiers, or even for measuring
antenna patterns on a range. When paired with a precision step attenuator, it
becomes a stable service generator for troubleshooting or tuning up receivers
and preamps. Although the MFJ-225 will tune from 1 to 180MHz the accuracy of
the SWR and the S11 and S21 measurements is best in the Amateur bands
through the 2M Amateur Band. Above 160MHz the accuracy may be reduced.

1.3 Panel and Control Layout: The analyzer's RF jacks, screen, and controls

are all configured for user-friendly (ergonomic) operation. Measurement cables
exit from the left side where they won't interfere with hand movements. The LCD
screen is centrally positioned for easy viewing. Three prominent push-button
switches controlling most analyzer functions are located to the right of the
screen, and the optical encoder Tune knob extends from the right-hand side of
the case -- all perfectly positioned for right-handed operation. In addition to
controlling the DDS, the Tune knob features a built-in press-on momentary
switch that functions as the fourth selector for controlling analyzer functions.

MFJ-225 Panel Layout

Function

SMA

Female

SO-239

Input

Output

LCD Display

Power

Power

Source

Exit

Mode

<USB Jack

1

2

3

<Charger Jack

Tune-4

1.4 Operating Modes: When you first power the MFJ-225, the MFJ Logo

followed by a main Menu appear in sequence. Each mode is selected by
pressing the appropriate selector switch. The analyzer's four operating modes
are show below.

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Version 1B

MFJ-225 Graphical Antenna Analyzer

Power Off/On

(Main Menu)

1.ANT-G 2.CABLE

3.ANT-S 4.PC>USB

BAT/USB

FUNCTION

MODE

1

EXIT

2

3

TUNE/SET

1. ANT-G SWR Mode, Press FUNCTION (1)

2. CABLE Mode, press EXIT (2)

3. ANT-S, press MODE (3)

4

4. PC>USB Mode, press TUNE/SET knob (4)

To Return to Main Menu, press EXIT (2)

ANT-G Mode: This screen presents a easy-to-view analog SWR bar-graph for

making "on-the-fly" tuner or matching network adjustments. In addition, numeric
readouts show Test Frequency, DDS Tuning Step, Numeric SWR, Impedance

Magnitude, Complex Impedance, Return Loss, C and L values, plus battery
condition. See Section 4.0 for a detailed rundown.

Cable Mode: On command, the DDS sweeps and calculates the open-stub
resonant frequency of random lengths of cable, then applies a default velocity
factor (Vf) to show an approximate measurement. To obtain final results, dial in
the factory specified Vf for your cable. The exact length will be displayed in both
feet and meters. You can also measure the Vf for a cable of known length. By
advancing to Loss Mode, you can measure your cable's losses on any frequency
from 1.0 to around 160 MHz. The screen displays test frequency along with the
computed results. See Section 5.0 for step-by-step instructions.

ANT-S Mode: This mode renders graphic plots for SWR, Impedance Magnitude,
Resistance, Reactance, Return Loss, and Phase. It also displays Center
Frequency, DDS Tuning Step, and Sweep Width -- parameters you can edit in

real time while viewing the screen. The top line of the display provides several
center-frequency measurement parameters while bottom line shows the
frequency scale plus an identifier for the type of plot. See section 6.0 for details.

PC>USB Mode: A built-in data link interfaces the analyzer with your PC to
provide access to the functions and features of IG-miniVNA. See Section 7.0 for
instructions to enter the pc interface mode.

2.0 Powering Your Analyzer

2.1 Power Sources: The MFJ-225 can run from either of two power sources. For

handheld operation, it is self-powered by four (4) AAA NiMh cells that provide up
to two hours running time. For desktop use, you may power it directly from your
computer's USB port through a Type-B interface cable, or use an external USB
AC-power adapter capable of providing 500 mA (not supplied). Note the MFJ-225

will not function on the 12V battery charger. The 12V input is only for battery
charging.

2.2 Power Switches: The unit's main ON/OFF switch and USB/BAT selector

are located to the right of the LCD screen. Select USB (button up) when
powering from your personal computer or from a USB adapter. You need not be
running PC>USB to obtain power, simply turn on your pc. When operating on

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Version 1B