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Страница 2: ...ntenna SWR 7 4 3 Coax Loss 9 4 4 Capacitance 9 4 5 Inductance 10 5 0 ADVANCED OPERATION 11 5 1 Forward 11 5 2 General Connection Guidelines 12 5 3 Magnitude of Impedance mode 12 5 4 Return Loss and Reflection Coefficient mode 12 5 5 Distance to Fault mode 13 5 6 Resonance Mode 13 5 7 Percentage Transmitted Power 14 6 0 ADJUSTING SIMPLE ANTENNAS 14 6 1 Dipoles 14 6 2 Verticals 15 6 3 Tuning a simpl...
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: ...eferenced to 50 ohms The MFJ 259D as a non precision signal source VFO output is leveled at approximately 3 Vpp or around 20 milliwatts into a 50 ohm load This signal is relatively pure with harmonics better than 25 dBc dB below the fundamental frequency carrier The internal source impedance Zo is 50 ohms A more complete description of the MFJ 259D s features along with proper measurement methods ...
Страница 5: ... of the Charger Jumper To gain access remove the eight screws securing the analyzer s back cover and separate it from the unit Look for a 3 pin header with a small black plastic shorting plug that fits over two of its pins It is located at the top of the main pc board near the OFF ON switch and power connector The shorting plug must be properly positioned for the type of battery you intend to use ...
Страница 6: ...just the frequency by more than 50 kHz at least once for the analyzer to remain awake Any time a two minute inactivity period elapses the power saving circuit automatically switches in When the analyzer goes to sleep a blinking SLP message will appear in the display s lower right corner as shown below To reawake the unit momentarily press either the Mode or Gate button To Disable Sleep mode 1 Turn...
Страница 7: ... new selection comes up on the display with an Identifier Screen After 3 seconds the Identifier Screen is replaced by the mode s working screen The menu is circular so after sequencing through all five choices the sequence starts over The five basic operating modes are described in detail below 1 Impedance R X Initial Mode Use this mode for measuring SWR and complex impedance The Impedance R X mod...
Страница 8: ... 10 millivolts and this level gradually increases to around 200 millivolts at 230 MHz The never exceed limit for safe testing is 2 volts peak to peak The counter s default gate time is 0 1 second but you may reset it to either 01 second very fast or 1 0 second very slow by tapping the Gate button A 1 0 second gate times provide increased frequency resolution more digits to the right of the decimal...
Страница 9: ...ance measurements Displacing the load away from the analyzer s calibration plane through random lengths of coax will have little or no impact on SWR readings but will introduce enough error through phase shift and transformer action to invalidate virtually any complex impedance measurement you might make When measuring Complex Impedance install the MFJ 259D as close electrically to the DUT as poss...
Страница 10: ...nnas such as Yagis and verticals are adjustable for both resonant frequency and impedance match Begin by setting these antennas for the element length prescribed in the instruction sheet or the calculated length Then adjust the matching network for minimum SWR The two adjustments tuning and matching are separate but often interact so be prepared to alternately readjust both element length and netw...
Страница 11: ...ance Access the Capacitance Mode by stepping the Mode switch to the Capacitance identification screen The top line of the working display shows the Frequency in MHz and the Capacitive Reactance Xc of the DUT at that specific frequency The lower line displays the computed Capacitance in pF Normally the measurement range is from a few pF to a few thousand pF The MFJ 259D becomes inaccurate when meas...
Страница 12: ...e is questionable Positive Reactance Sign The MFJ 259D measures Reactance X and mathematically converts it to an Inductance value but its processor can t determine if the reactance is inductive or capacitive You can usually determine the type or sign of the reactance by adjusting the VFO If tuning up in frequency cause the reactance to decrease the load is likely capacitive j at the measurement fr...
Страница 13: ...of Apparent Power in the system see equivalency chart below All of these terms have a corresponding SWR value attached to them so if they seem unfamiliar and you have no specific need to apply them sticking with basic SWR measurements will serve you just as well MFJ 259D Limitations for Advanced Measurements The analyzer s coupler uses a 50 ohm bridge with voltage detectors across each leg An eigh...
Страница 14: ... measuring components or systems other than Zo 50 ohms Also assume that installing a random length transmission line between the DUT and the analyzer s calibration plane can and usually will substantially alter Impedance measurements When measuring SWR use properly constructed 50 ohm coaxial cables of known quality and check connector condition 5 3 Magnitude of Impedance mode Impedance Magnitude i...
Страница 15: ... resistive and reactive loads or L C terminations may skew the results or simply not work To conduct the test follow the specific sequence of steps outlined below To measure fault distance 1 Connect the DUT to the analyzer s Antenna connector From Advanced mode tap the Mode switch twice to bring up the Distance to Fault ID screen The top line of the working screen will display the VFO frequency in...
Страница 16: ...ntennas are tuned for operating frequency by varying the element length and most homemade verticals and dipoles are very simple to adjust 6 1 Dipoles Because the dipole is a balanced antenna it s always a good idea and good engineering practice to install a balun at the feed point A balun could be as simple as several turns of coax wrapped several inches in diameter or it could be a complicated af...
Страница 17: ... bleed off static then connect to the Antenna jack 2 Set the analyzer s band switches and VFO tuning for the desired band 3 Select any analyzer operating mode that will display SWR 4 Read the SWR and adjust the VFO tuning for minimum SWR Write down the frequency 5 To re tune your antenna accurately without a lot of cut and try calculate a Scaling Factor 6 First determine if the antenna needs to be...
Страница 18: ... with the shield grounded For balanced line run the analyzer on its internal batteries keep it a few feet away from other conductors and earth and do not attach any stray wires other than the feedline Connect the DUT with one lead to the analyzer s ground stud and the other to the Antenna center pin The DUT must be suspended and kept away from metallic objects and ground Note that the far end of t...
Страница 19: ...known line Taking one approach we intentionally introduce a resistive mismatch at the far end of the line measure the impedance transformation over a 360 phase rotation at the near end and calculate the impedance at the center Or we introduce different trial loads of known resistance at the far end until we find a value where the cable becomes flat across a wide range of frequencies In essence we ...
Страница 20: ...nected to the MFJ 259D 1 Patch the analyzer Antenna jack to the tuner input connector 2 Connect the desired antenna at the tuner output connector 3 Tune the analyzer VFO to the desired frequency and leave it there 4 Select the analyzer s basic SWR Resistance R Reactance X Mode 5 Adjust the tuner s controls until the analyzer s SWR indicators show unity 1 1 6 Turn off and disconnect the MFJ 259D Re...
Страница 21: ...he clip lead installed at position B but show poor SWR with the clip lead is installed at A or C note however that the SWR readings should measure about the same whether connected to A or C A voltage balun should also be tested using the configuration shown in Fig B with the resistors in parallel If it is operating properly SWR will be remain low with the resistors connected from either output ter...
Страница 22: ... 0549 or the MFJ Factory at 622 323 5869 We can serve you best if you have your unit manual and all pertinent information about your difficulty handy so you can answer questions the technicians may ask You can also send questions by mail to MFJ Enterprises Inc 300 Industrial Park Road Starkville MS 39759 by FAX to 662 323 6551 or by e mail to techinfo mfjenterprises com Send a complete description...
Страница 23: ...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 Postage and handling may vary according to the weight of the product in question We also take MasterCard Visa American Express and Discover credit cards 4 This warranty is NOT void for owners who attempt to repair defective units Te...
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