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MFJ MFJ-269D Скачать руководство пользователя страница 24

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

22

5.5.1.3

DTF Antenna Length

To measure the electrical length of wire antennas (longwires, dipoles, Beverages), connect through a
good broadband matching transformer -- or by connecting directly to the analyzer's

Antenna

port.

To  ensure  accuracy,  avoid  using  any  appreciable  lengths  of  feedline  (more  than  1/32  wl)  between  the
analyzer and the antenna.  While measurements can be made with a transmission line connected between
the  antenna  and  analyzer,  false  zero  reactance  crossings  will  be  introduced  from  line  mismatch.
Watching the SWR meter will help you weed-out false reactance nulls when measuring antennas through
a transmission line.

To determine antenna length, treat the antenna like a transmission line, following the procedure for
measuring

Distance To Fault

. For a dipole, your result will be the electrical length of one leg. For a

longwire or Beverage, it will be electrical length for the entire antenna.

5.5.1.4

DTF Measurement Procedures

Distance to Fault

is the first measurement mode in

Advanced-2

. To enter the mode, press and hold the

Mode

and

Gate

buttons until

Advanced-2

appears on the screen. From other Modes, step through the

menu holding the

Mode

and

Gate

button.

The first menu that appears is:

The

Gate

button increases Vf,

Mode

decreases it.

1.

Set the

Vf

to the factory specified velocity factor of the transmission line. This data is required to for

Physical Length

calculations that will be displayed later. For

Electrical Length in Feet

, set Vf to unity

(1.00).

Note:

An

Incorrect

Vf

setting will not cause an errors in electrical measurements such as

Length in

Degree.

However it

will

cause an error in physical length calculations, such as

Dist. to Fault

.

2.

After setting the

Vf

, press

Gate

and

Mode

simultaneously to lock-in the value. The display indicates:

and after a few seconds changes to (sample screen):

15.814 MHz 1st

DTF Xs= 51

Note that

1st

is flashing on and off. This display is prompting you to use

Tune

to

find the frequency

where the

Impedance Meter

shows the lowest reading for

Xs

(as close to Xs=0 as possible). When you

find that frequency, press and hold

Gate

until the flashing

1st

on the display stops flashing. Then release

Gate

quickly.

The display now indicates the first frequency data point and the blinking

1st

will change to a blinking

2nd

:

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Содержание MFJ-269D

Страница 1: ......

Страница 2: ...NERAL CONNECTIONS 6 3 2 POWER UP DISPLAY 7 3 3 MAIN MEASUREMENT MODES LF HF VHF 0 10 230 MHZ 7 3 4 FREQUENCY CONTROL 8 4 0 MAIN OR OPENING MODE 9 4 1 GENERAL CONNECTIONS 9 4 2 ANTENNA SWR AND IMPEDANC...

Страница 3: ...NES OR BEVERAGE ANTENNAS 30 7 4 ADJUSTING TUNERS 30 7 5 ADJUSTING AMPLIFIER MATCHING NETWORKS 31 7 6 TESTING RF TRANSFORMERS 31 7 7 TESTING BALUNS 31 7 8 TESTING RF CHOKES 32 8 0 TECHNICAL ASSISTANCE...

Страница 4: ...ntennas SWR impedance reactance resistance resonant frequency and bandwidth Antenna tuners SWR bandwidth frequency Amplifiers Input and output matching networks chokes suppressors traps and components...

Страница 5: ...interference isn t an issue but occasionally a particularly powerful signal may be picked up by the antenna under test and routed into the analyzer bridge circuit where it conflicts with the internal...

Страница 6: ...O ANY POWER SOURCE IMPROPER CONNECTIONS OR INCORRECT VOLTAGES MAY CAUSE DAMAGE TO THIS PRODUCT 2 1 External Power Supply The MFJ 1312D satisfies all external voltage and current power source requireme...

Страница 7: ...are depleted charge with the analyzer power switch turned off it may take ten hours or more to fully restore depleted cells Important Warning Never change batteries with the power switch On or with a...

Страница 8: ...dby A blinking SLP message in the display screen lower right corner indicates power saving mode see below To pull the unit out of SLP momentarily press either the Mode or Gate button to resume operati...

Страница 9: ...wo analog panel meters also activate when the working display comes up 3 3 Main Measurement Modes LF HF VHF 0 10 230 MHz Momentarily pressing or tapping the Mode button after the first working display...

Страница 10: ...F and HF bands 0 10 11 0 MHz The Upper Range switch selects 5 HF and VHF bands for 11 230 MHz coverage Note that the Upper Range switch must be set fully clockwise to the Lower Range position for the...

Страница 11: ...quality parts and check them for wear oxidation dirt and tight pin contact before proceeding 2 Lead Length Make all connection electrically secure and keep all leads as short as possible This precaut...

Страница 12: ...2 wavelength of cable displace the calibration plane by a controlled amount 360 degree phase rotation 2 Electrical Half Wavelengths of Cable Installing a half wavelength of cable between the load and...

Страница 13: ...far end of the cable If the SWR is elevated or the Impedance Z fluctuates very much as you tune the analyzer s VFO suspect a defective cable 8 Excessive Transmission Line Loss Your cable may exhibit...

Страница 14: ...ta when the measurement accuracy is questionable see examples below Reactance Sign The MFJ 269D measures the DUT s reactance X and mathematically converts it to a capacitance value Xc However the anal...

Страница 15: ...r capacitive You can usually confirm the sign by adjusting the VFO If tuning down in frequency decreases reactance the reactance is likely inductive jX because inductors normally exhibit decreased rea...

Страница 16: ...ng until you understand its full technical meaning Information Sources A basic understanding of transmission line and antenna behavior and terminology is very important in understanding Advanced Mode...

Страница 17: ...nts with the exception of the Frequency Counter mode The Antenna connector supplies about 7 dBm output into 50 ohms 5 volts RMS and appears like a 50 ohm source resistance open circuit voltage 1 volt...

Страница 18: ...ode by holding down Mode and Gate switches The opening display first indicates and then flashes to In this mode the LCD displays Frequency Impedance Magnitude Z in ohms and Phase Angle of the Impedanc...

Страница 19: ...meter displays the Z in ohms while the SWR meter displays 50 ohm referenced SWR Series Equivalent Impedance display examples 7 1598 MHz 3 2 Rs 50 Xs 62 14 095 MHz 31 Rs Z 1500 sW R sW R In the left h...

Страница 20: ...e meter as an analog tuning aid for identifying resonance In this mode the MFJ 269D measures and displays Frequency SWR Resistance Rs and Reactance Xs When reactance equals zero in a system that has s...

Страница 21: ...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...

Страница 22: ...he SWR meter indicates SWR normalized to 50 Ohms and the impedance meter is disabled To use this mode connect the DUT to the Antenna connector adjust Frequency as needed and read the results on the sc...

Страница 23: ...rs in other measurements Only SWR and SWR related functions are displayed for the UHF band 5 5 1 Distance to Fault DTF for HF VHF only With Vf entered in the previous function the next function in the...

Страница 24: ...o enter the mode press and hold the Mode and Gate buttons until Advanced 2 appears on the screen From other Modes step through the menu holding the Mode and Gate button The first menu that appears is...

Страница 25: ...s at the current frequency setting 68 511 Mhz o As you Tune the analyzer frequency the electrical length of the line will be re calculated Note that Electrical Length repeats at 360 degrees and return...

Страница 26: ...rogrammed in manually If a length is not programmed in a default length of 100 feet will be selected automatically When changing UHF frequency with a 100 foot line the display rotates through 360 degr...

Страница 27: ...ed length in feet of matching sections and phasing lines if you know the required variables velocity factor and electrical degrees The analyzer can also directly measure and display length using the d...

Страница 28: ...it in The display will now change to Line length l 78 o Pressing Mode shifts the display to the Velocity Factor adjustment in step 2 5 6 Advanced 3 LF HF VHF only To access this mode press and hold M...

Страница 29: ...cle the analyzer back to the Main or to another Advanced mode 6 0 ADJUSTING SIMPLE ANTENNAS Most antennas are adjusted by varying element length and most homemade antennas are simple verticals or dipo...

Страница 30: ...o 4 Divide the measured minimum SWR frequency by the desired operating frequency 5 Multiply the present antenna length times the result from Step 4 This will approximate the antenna length you actuall...

Страница 31: ...Distance to Fault mode in Advanced 2 see section 5 5 If balanced line is used operate the MFJ 269D only from internal batteries and keep it a few feet away from other conductors or earth Do not attac...

Страница 32: ...round the expected value 2 Connect the transmission line or antenna directly to the MFJ 269D Antenna connector Adjust the frequency near the expected operating frequency until the lowest resistance an...

Страница 33: ...r s RF matching networks The appropriate network can now be adjusted When the analyzer shows 50 ohms and a 1 1 SWR at the operating frequency with the proper amounts of capacitance to set the system Q...

Страница 34: ...voltage balun is operating properly the SWR will be very low with the resistors connected from either output terminal to ground 7 8 Testing RF Chokes Large RF chokes usually have frequencies where the...

Страница 35: ...62 323 0549 or the MFJ Factory at 662 323 5869 You will be best helped if you have your unit manual and all information on your station handy so you can answer any questions the technicians may ask Yo...

Страница 36: ...erms are satisfied MFJ must receive the original parts you wish to replace your proof of purchase and a personal check cashiers check or money order must be provided to cover postage and handling Post...

Страница 37: ......

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