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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

COPYRIGHT 2014 MFJ ENTERPRISES, INC.

C

Model MFJ-249C

VERSION 1A

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Содержание MFJ-249C

Страница 1: ...AUTION 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 COPYRIGHT 2014 MFJ ENTERPRISES INC C Model MFJ 249C VERSION 1A ...

Страница 2: ...s 5 3 4 Blinking VOLTAGE LOW display warning 6 4 0 MAIN OR OPENING MODE 6 4 1 General Connection Guidelines 6 5 0 ADJUSTING SIMPLE ANTENNAS 7 5 1 Dipoles 7 5 2 Verticals 7 5 3 Tuning a simple antenna 7 6 0 TESTING AND TUNING STUBS AND TRANSMISSION LINES 8 6 1 Testing Stubs 8 6 2 Velocity Factor of Transmission Lines 8 6 3 Impedance of Transmission Lines or Beverage antennas 9 6 4 Adjusting Tuners ...

Страница 3: ...eeded to deliver the additional RF power greatly reduces battery life In fact over 70 of the analyzer s 150 mA current drain is already allocated to the VFO and its amplifier stages for generating a low harmonic level amplitude test signal Most RF interference problems occur at lower frequencies and are caused by high power AM broadcast stations These signals couple efficiently into large antenna ...

Страница 4: ...ithout frequency gaps using a precision reduction drive VFO tuning capacitor and two band switches Bands of coverage are Main Switch 155 230 MHz 113 155 MHz 67 113 MHz 28 67 MHz 11 28 MHz Lower Range Lower Range Switch 4 7 11 MHz 2 1 4 7 MHz 1 0 2 1 MHz 0 53 1 0 MHz Note that LF coverage may be shifted from 0 53 1 0 MHz down to 0 47 0 94 MHz for 600 Meter and maritime frequency coverage To retune ...

Страница 5: ...h two screws 2 3 Using Rechargeable AA Type Batteries IMPORTANT WARNING Do not use an external power sources that deliver less than 13 8 volts with rechargeable batteries installed If the external supply voltage is too low the charger will not work properly and batteries will eventually discharge We recommend charging batteries with the MFJ 249C power switch off and allowing enough charging time t...

Страница 6: ...nd hold the Mode button while reapplying power 3 Continue holding the Mode button until the copyright message appears on the screen 4 Release Mode If Sleep Mode was disabled successfully the message shown below will appear on screen The Sleep Mode function becomes re enabled anytime the analyzer is turned Off and On again 3 0 MAIN MENU AND DISPLAY IMPORTANT WARNING Never Apply RF or any other exte...

Страница 7: ...the ANTENNA connector The display will show the selected frequency and the actual SWR in a numerical and a bar graph format The maximum numerical SWR displayed is 25 Any SWR adjustments have to be made at the antenna since any adjustments at the transmitter end of the feedline cannot affect the losses nor the efficiency of the antenna system 2 Impedance Magnitude This mode will provide magnitude o...

Страница 8: ... with supply voltages below 11 volts may not be as reliable 4 0 MAIN OR OPENING MODE IMPORTANT WARNING Never apply RF or any other external voltages to the Antenna port of this unit This unit uses zero bias detector diodes that are easily damaged by external voltages over a few volts Also confirm the power supply is correct as described in Section 2 0 before operating this unit A basic understandi...

Страница 9: ... that is detuning the antenna or the feedline itself is not really 50 ohm cable Common mode current caused by conduction typically occurs when no balun has been installed at the feed point to choke it off Common mode induction currents may also result from other installation errors such as running the feedline parallel rather than perpendicular to the radiating element Repositioning the feedline m...

Страница 10: ...of the PL 259 and one conductor The other conductor of the balanced line connects directly to the center pin of the connector Coaxial lines can lay in a pile or coil on the floor two wire lines must be suspended in a straight line a few feet away from metallic objects or ground The lines must be open circuited at the far end for odd multiples of 1 4 wave stubs i e 1 4 3 4 1 1 4 etc and short circu...

Страница 11: ...nna connector 2 Terminate the far end with a potentiometer or resistance decade box 3 Adjust the analyzer s VFO frequency and note only the SWR change SWR need not be low 4 Adjust termination resistance until SWR remains constant over the widest possible range 5 The resistance of the termination resistor is the line impedance or surge impedance of the system 6 4 Adjusting Tuners The MFJ 249C can b...

Страница 12: ...nt balance It also has the highest power capability and lowest loss for given materials To evaluate the balun DUT measure SWR while connecting the grounded clip lead to point A B and C When functioning properly a current balun will exhibit low SWR over its entire operating range with the clip lead installed at any of those three positions A well designed voltage balun should show low SWR over its ...

Страница 13: ...ot get a low SWR change to the next smaller value standard capacitor and try again Repeat the process until you get low SWR 4 Solve this equation using F as the resonant frequency and C as the capacitance of the standard capacitor L H 1 00003948F C F MHz C pF 2 μ 6 9 Resonant Frequency of Tuned Circuits The MFJ 249C can be used to measure the resonant frequency of tuned circuits by two methods The...

Страница 14: ...er will identify the low impedance series resonant frequencies 1N34 01 10K Measure the voltage between these points with a Hi Z meter All leads should be short choke ANTENNA To the MFJ 249B s connector Refer to the section on measuring the inductance of RF chokes 7 0 TECHNICAL ASSISTANCE If you have any problem with your MFJ 249C first check the appropriate section of this manual If the manual doe...

Страница 15: ...s warranty is NOT void for owners who attempt to repair defective units Technical consultation is available by calling 662 323 5869 5 This warranty does not apply to kits sold by or manufactured by MFJ Enterprises Inc 5 Wired and tested PC board products are covered by this warranty provided only the wired and tested PC board product is returned Wired and tested PC boards installed in the owner s ...

Страница 16: ...MFJ 249C Manual Version 1A Printed In U S A 300 Industrial Park Road Starkville MS 39759 ...

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