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MFJ MFJ-269 Скачать руководство пользователя страница 24

MFJ-269 Instruction Manual HF/VHF/UHF SWR Analyzer

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NOTE: You can also cycle through the

Advanced 1

UHF menu by holding the

MODE

button until the

display indicates the desired function.

After a few seconds, the display changes to:

The

“Return Loss and Reflection Coeff”

mode measures and displays return loss in dB and voltage reflection

coefficient on the LCD. These terms are another way of describing SWR. The SWR meter indicates 50 ohm
SWR and the impedance meter is disabled.

To use this mode, connect the load to be measured to the ANTENNA connector, adjust the frequency to the
desired frequency range, and read the results on the MFJ-269 LCD and panel meter displays.

5.4.1.6 Match Efficiency (UHF)

Match Efficiency

is the second and final measurement mode available in the

Advanced 1

UHF menu. This

mode is reached (after entering the

Advanced 1

menu) by pressing and releasing the

MODE

button one time. It

can also be reached (as all other advanced modes are) by stepping through the other

Advanced 1

modes with the

MODE

button until the display indicates

“Match Efficiency

”.

Match efficiency is another way of describing SWR. It is similar to mismatch loss, but SWR data is expressed as
a “percentage of forward power” compared to the “reactive” or “circulating power” of the system.

CAUTION:

“Match efficiency” may mislead those unfamiliar with SWR and energy transfer in a system. Power

“transmitted” or transferred to a load can be nearly 100% even when a match efficiency calculation or display
indicates a system has

nearly zero percent match efficiency

. Conversely, match efficiency can measure nearly

100%, and the actual power at the load might be very low due to system losses.

Match efficiency ONLY applies to the loss in power transfer from a perfect 50 ohm fixed tuned source to the
input of the feedline or system where the measurement is made. It is mostly useful in laboratory situations. It is
not a description of antenna system or feedline efficiency. Even with nearly zero percent match efficiency, an
antenna system can radiate applied power with good efficiency. With any given amount of match efficiency your
antenna system can be near 100% or near zero percent efficient.

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Содержание MFJ-269

Страница 1: ...inking VOLTAGE LOW display warning 10 2 6 Power Saving Mode Sleep mode 6 3 0 MAIN MENU AND DISPLAY 7 3 1 General Connection Guidelines 7 3 2 Power up Display 7 3 3 Main Mode Descriptions HF functions...

Страница 2: ...attempting to use this product Incorrect power supply voltages or excessive external voltages applied to the ANTENNA connector will damage this unit 1 0 Description The MFJ 269 RF analyzer is a compa...

Страница 3: ...nce and value Transmitters and oscillators Frequency The MFJ 269 measures and directly displays the following Electrical length feet or deg Impedance phase angle degrees Resonance MHz Feedline Loss dB...

Страница 4: ...th impedance measurement devices Most RF interference problems occur on lower frequencies since high power AM broadcast signals and other external voltage sources couple better into large antennas esp...

Страница 5: ...ably well filtered the case of the MFJ 269 is connected directly to the negative terminal The supply must not have a grounded positive lead The MFJ 269 can be used with external low voltage dc supplie...

Страница 6: ...E TO ESTABLISH FULL BATTERY CHARGE AT LEAST TEN HOURS NEVER CHANGE BATTERIES WITH THE POWER SWITCH ON OR WITH AN EXTERNAL SUPPLY PLUGGED INTO THE MFJ 269 The internal charger trickle can be used to ch...

Страница 7: ...ing Mode sleep mode The operating current drain of the MFJ 269 is approximately 135 mA for HF operation Battery life is extended by using an internal Power Saving mode Sleeping battery drain is less t...

Страница 8: ...it Improper or incorrect power supply voltage or wiring could permanently damage this unit The FREQUENCY COUNTER INPUT connector BNC type is for frequency counter use only Correct use of this connecto...

Страница 9: ...button the display will show the type of data measured in the newly selected mode step The five main or opening measurement modes are described below 3 3 Main MODE descriptions HF Functions Only CAUT...

Страница 10: ...acitive reactance Xc in ohms capacitance C in picofarads or pF The Impedance meter indicates reactance in ohms and the SWR meter displays SWR 4 Inductance in H is the fourth mode The digital display i...

Страница 11: ...sion line and antenna behavior and terminology is very important in understanding information provided by the MFJ 269 Most explanations are available in the ARRL Handbooks and they should suffice for...

Страница 12: ...art of the system impedance is displayed in ohms f Adjust the TUNE knob until the counter displays the desired frequency or until you find the lowest SWR Advanced antenna measurement modes are availab...

Страница 13: ...impedance would remain 50 ohms SWR would be 1 1 in this case since a dissipative resistance readily accepts power from the source 3 Electrical Half wave lines only repeat the far end impedance over a...

Страница 14: ...3 Advanced 3 allows user selection of analyzer impedance and measurement of loss non 50 ohm systems Caution Do not measure loss of conventional transformers attenuators or coaxial cables with impedanc...

Страница 15: ...r above 1500 ohms If the reactance of the component is outside reliable ranges C X 7 X or C Z 1500 will be displayed When the warning is displayed capacitance is not measured To measure capacitance a...

Страница 16: ...actance is in the inaccurate range L X 7 X or L Z 1500 will be displayed An inductance value will not be displayed if measurement range is questionable To measure inductance a Turn the MFJ 269 on and...

Страница 17: ...roximate loss of a 50 ohm feedline The line must not be terminated it must remain open at the far end to measure line loss An overflow indicator in the display less than sign LOSS 1 76dB means the los...

Страница 18: ...unit as accurate as possible most formulas contain squares and other complex functions A certain amount of error is unavoidable especially at high or low impedance values and especially at higher VHF...

Страница 19: ...output connection This port is used to measure SWR or perform other RF impedance measurements with the exception of the Frequency Counter mode The ANTENNA connector supplies about 7 dBm output into 5...

Страница 20: ...apacitance will be lower than 1500 ohms at frequencies higher than 30 MHz and lower as adapters and leads are added to the ANTENNA port This small stray capacitance will not affect high frequency meas...

Страница 21: ...ries equivalent impedance display examples 7 1598 M H z 3 2 Rs 50 Xs 62 14 095 M H z 31 Rs Z 1500 sW R sW R With impedances in the above left hand display resistance would remain 50 ohms reactance wou...

Страница 22: ...Advanced 1 menu by stepping through the other modes When this mode is initialized the display briefly indicates The Resonance Mode primarily draws attention to reactance displaying reactance on the IM...

Страница 23: ...o percent match efficiency Conversely match efficiency can measure nearly 100 and the actual power at the load might be very low due to system losses Match efficiency ONLY applies to the loss in power...

Страница 24: ...er Advanced 1 modes with the MODE button until the display indicates Match Efficiency Match efficiency is another way of describing SWR It is similar to mismatch loss but SWR data is expressed as a pe...

Страница 25: ...set the correct feedline velocity factor Velocity factor is increased by pressing the GATE button and decreased by pressing the MODE button When the correct Vf is reached press both buttons at the sa...

Страница 26: ...outside of the connector 5 5 1 3 DTF Antenna Length Antenna length such as the electrical length of longwires dipoles or Beverages can be measured Measurements should ideally be made either through a...

Страница 27: ...ult 2 After setting the Vf press GATE and MODE simultaneously to lock in the desired Vf The display will indicate and after a few seconds change to 15 814 M H z 1st D TF Xs 51 This display prompts you...

Страница 28: ...ulate the length of one wavelength of line for the velocity factor and at the frequency of the display Remember this is the length of a full wavelength 360 degrees at the frequency selected and with V...

Страница 29: ...ms of wavelength cutting the line to an exact electrical degree is almost impossible This is true over extremely narrow frequency ranges 1 Simultaneously press and hold GATE and MODE buttons until Adv...

Страница 30: ...ow the required variables velocity factor and electrical degrees The analyzer can also directly measure and display length using the distance to fault mode sec 5 5 1 for HF VHF If this mode is entered...

Страница 31: ...line length adjustment function that allows you to change the length in degrees Li ne l eng th l 360 o o 7 To increase line length in degrees press the GATE button To decrease line length in degrees p...

Страница 32: ...the message shown above appears Zo can be adjusted by pressing either the GATE increase or MODE decrease buttons 2 After the correct Zo is reached press both MODE and GATE at the same time for a very...

Страница 33: ...he feedpoint The balun can be as simple as several turns of coax several inches in diameter or a complicated affair with many windings on a ferromagnetic core The height of the dipole as well as it s...

Страница 34: ...cy 5 Multiply the present antenna length by the result of step 4 This will be close to the antenna length actually needed Note This method of tuning will only work on full size vertical or dipole ante...

Страница 35: ...required length 6 Cut the stub to the length calculated in step 5 and confirm lowest X is on he desired frequency The Distance to Fault mode can also be used It will directly display the line length...

Страница 36: ...ured with the MFJ 269 Lines of higher impedance can be measured if a broadband transformer or resistance is used to extend the MFJ 269 s range Select any measurement mode that indicates resistance R a...

Страница 37: ...nced 2 7 4 Adjusting Tuners The MFJ 269 can be used to adjust tuners Connect the MFJ 269 ANTENNA connector to the tuner s 50 ohm input and the desired antenna to the normal tuner output This connectio...

Страница 38: ...0 to 1000 ohm winding is connected through very short less than one electrical degree long leads to the ANTENNA connector on the MFJ 269 The other winding s of the transformer is terminated with a low...

Страница 39: ...A To the MFJ 259B s connector 7 8 Testing RF Chokes Large RF chokes usually have frequencies where the distributed capacitance and inductance form a low impedance series resonance This series resonanc...

Страница 40: ...oes not reference your problem or your problem is not solved by reading the manual you may call MFJ Technical Service at 601 323 0549 or the MFJ Factory at 601 323 5869 You will be best helped if you...

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