MFJ MFJ-209 User Manual

Model MFJ-209

VERSION 1A

INSTRUCTION MANUAL

CAUTION: Read All Instructions Before Operating Equipment

MFJ ENTERPRISES, INC.

300 Industrial Park Road

Starkville, MS 39759 USA

Tel: 662-323-5869 Fax: 662-323-6551

DISCLAIMER

Information in this manual is designed for user purposes only and is not intended to supersede information contained in customer regulations, technical manuals/documents, positional handbooks, or other official publications. The copy of this manual provided to the customer will not be updated to reflect current data.

Customers using this manual should report errors or omissions, recommendations for improvements, or other comments to MFJ Enterprises, 300 Industrial Park Road, Starkville, MS 39759. Phone: (662) 323-5869; FAX: (662) 323-6551. Business hours: M-F 8-4:30 CST.

MFJ-209 SWR Analyzer Instruction Manual

MFJ-209 HF/VHF SWR Analyzer

TABLE OF CONTENTS

Table of Contents .........................................................................................................2

Introduction ..................................................................................................................3

Powering The MFJ-209................................................................................................4

Battery Installation .......................................................................................................5

Operation Of The MFJ-209..........................................................................................5

SWR and the MFJ-209.....................................................................................6

Measuring SWR ...............................................................................................7

Adjusting Simple Antennas..........................................................................................7

Dipoles..............................................................................................................7

Verticals............................................................................................................8

Tuning an Antenna...........................................................................................8

Measuring the Feedpoint Resistance of Antennas ...........................................8

Testing and Tuning Stubs and Transmission Lines......................................................9

Velocity Factor of Transmission Lines ............................................................10

Impedance of Transmission Lines....................................................................10

Estimating transmission line loss.....................................................................11

Adjusting Tuners..........................................................................................................11

Adjusting Amplifier Matching Networks.....................................................................12

Testing RF Transformers..............................................................................................12

Testing Baluns..................................................................................................12

Measuring Inductance and Capacitance.......................................................................13

Measure capacitance.........................................................................................13

Measure inductance..........................................................................................14

Resonant Frequency of tuned circuits ..........................................................................14

Testing RF Chokes...........................................................................................15

"Zero Beating" the MFJ-209........................................................................................16

Using the MFJ-209 as a Signal Source ........................................................................16

Technical Assistance....................................................................................................17

MFJ-209 SWR Analyzer Instruction Manual

INTRODUCTION

The MFJ-209 SWR Analyzer is an easy to operate, versatile test instrument for analyzing nearly any 50 ohm RF system on frequencies between 1.8 and 170 MHz. In addition the MFJ-209 can be used as signal source.

The MFJ-209 combines three basic circuits; a wide range oscillator, a 50 ohm RF bridge, and a calibrated bridge unbalance indicator. This combination of circuits allows measurement of the SWR (referenced to 50 ohms) of any load connected to the ANTENNA connector.

The MFJ-209 covers all ham bands from 2 meters to 160 meters. The dial calibration is approximate and for reference only. The actual frequency may vary from what is marked on the front panel. The MFJ-209 FREQUENCY switch selects the following frequency ranges:

1.8 - 4 MHz 4 - 10 MHz 10 - 27 MHz 27 - 70 MHz 70 - 114 MHz 114- 170 MHz

A frequency counter, such as the MFJ-346, can be connected to the "FREQ. OUT" jack (RCA phono) to get a more accurate reading of the frequency. As an alternative to a frequency counter, you can zero beat the output with an HF receiver. See the section on zero beating the MFJ-209 with a receiver.

The MFJ-209 can be used to adjust or measure the following:

Antennas: SWR, resonant frequency, bandwidth, efficiency Antenna tuners: SWR, frequency Amplifiers: Input and output networks Coaxial transmission lines: SWR, velocity factor, losses, resonance Balanced transmission lines: Impedance, velocity factor, resonance Matching or tuning stubs: SWR, resonant frequency, bandwidth Traps: Resonant frequency Tuned Circuits: Resonant frequency Small capacitors: Value RF chokes and inductors: Self resonance, series resonance, value Transmitters and oscillators: Frequency

Warning: Please read this manual thoroughly before using this instrument. Failure to

follow the operating instructions may cause false readings or even damage this unit.

A Quick Word about Accuracy

Inexpensive SWR meters have limitations. The following text details several common problems and reasons they occur.

MFJ-209 SWR Analyzer Instruction Manual

Measurement errors. Unreliable readings are rooted in three primary areas:

1.) Signal ingress from external RF sources, usually strong AM broadcast stations.

2.) Diode detector and A/D converter errors.

3.) The impedance of connectors, connections, and lead lengths.

Virtually all low cost impedance meters use broad-band voltage detectors. The reason virtually all analyzers use broadband detectors is cost. Narrow band detectors are very expensive, since the detector system would have to use at least one selective gain-stable receiver. Narrow band detectors would price antenna and impedance analyzers far outside the price range of most casual users.

Broadband detectors are sensitive to out-of-band external voltages, and solutions to most outof-band interference are not simple. Common low-pass or band-pass filters behave like small transmission lines of varying impedances on different frequencies. Low-pass or high-pass filters change impedance and SWR readings, just as an additional section of transmission line would. This modification of impedance caused by filters severely limits their usefulness.

One solution to this problem (often mentioned by users) is to increase internal generator power. Unfortunately the power required to operate a clean, harmonic-free broadband VFO system greatly reduces battery life. In this unit, more than 70% of the total battery drain (-150 mA) is used to produce the low harmonic distortion test signal.

Most RF interference problems occur on lower frequencies, since high power AM broadcast signals couple well into large antennas (especially 160 meter verticals). MFJ offers an adjustable filter that attenuates all off-frequency signals while having virtually no small effect on measurements between 1.8 and 30 MHz. Properly used, this adjustable filter reduces external interference while having nearly no measurable effect on desired measurements.

Component limitations are another source of inaccuracy. Diodes detecting very small voltages are non-linear. The accuracy of the MFJ-259B is enhanced by the use of special microwave zero-bias Schottky detectors with matching compensating diodes. Each unit is individually compensated to provide the best possible linearity with both high and low impedance loads, making the A/D converter's 1/2 percent resolution the primary limitation.

POWERING THE MFJ-209

The MFJ-209 requires between 8 and 18 volts for proper operation. Any power supply used with the MFJ-209 must be capable of supplying 200mA of current MFJ has an optional

power supply, the MFJ-1312D, that satisfies all external supply requirements. We recommend only using this supply.

The MFJ-209 has a standard 2.1 mm female receptacle on the top right edge of the case. This jack is labeled "12VDC" and has the word "POWER" near it. A pictorial polarity marking appears on the case near the power jack. The outside conductor of the plug must connect to

MFJ-209 SWR Analyzer Instruction Manual

the negative supply voltage and the center conductor of the plug must connect to the positive voltage. The internal battery pack is automatically disconnected when an external power plug is inserted in this jack.

SWR measurement will be inaccurate when the supply voltage falls below 7 volts. To avoid false readings maintain fresh batteries and always use the correct power supply.

WARNING: REVERSE POLARITY OR EXCESSIVE VOLTAGE CAN DAMAGE

OR DESTROY THE MFJ-259B. NEVER APPLY MORE THAN 18 VOLTS, NEVER USE AC OR POSITIVE GROUND SUPPLIES!

BATTERY INSTALLATION

If batteries are used, they must be installed by removing the 8 phillips head screws on each side of the case. The eight batteries fit in two separate battery holders with the positive terminal of the batteries positioned toward the round fixed connection, and the negative terminals toward the springs of the battery holder.

The battery case has two external terminals that connect to a "pigtail" that has two terminals on it. This connector looks like the type used for 9 volt transistor radio batteries and connects in the same way. Do not attempt to use 9 volt batteries with this unit. After the batteries are installed in the plastic holders and the connections are made to the battery packs, the battery holders can be slid directly into the chrome retaining clips on the cover.

MFJ recommends the use of ALKALINE AA (or rechargeable nicad) cells to reduce the risk of equipment damage from battery leakage. Avoid leaving any batteries in this unit during periods of extended storage. Remove weak batteries immediately!

Carefully check the following: * The battery packs are positioned so that they do not interfere with any internal parts of the

MFJ-209.

* The leads are positioned to reach with the cover in the original position. * The wires are not pinched between the cover and the chassis.

OPERATION OF THE MFJ-209

After the MFJ-209 is connected to a proper power source the red on-off button can be depressed to apply power. When pressed, the red button should lock into position.

The "ANTENNA" connector (SO-239 type) on the top of the MFJ-209 provides the SWR bridge output connection. To measure SWR, this connector must be connected to the load or device under test. Warning: Never apply power to the "ANTENNA" connector.

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