BIRD 4304A Operating & Service 电路图.pdf

INSTRUCTION BOOK RF DIRECTIONAL THRULINE WATTMETER MODEL 4304A Copyright 2002 by Bird Electronic Corporation Instruction Book Part Number 920-4304A Rev. E Thruline and Termaline are registered trademarks of Bird Electronic Corporation RadioFans.CN 收音机爱 好者资料库 THIS page intentionally left blank RadioFans.CN 收音机爱 好者资料库 i Safety Precautions The following are general safety precautions that are not necessarily related to any specific part or procedure, and do not necessarily appear elsewhere in this publication. These precautions must be thoroughly understood and applied to all phases of operation and maintenance. Keep Away From Live Circuits Operating personnel must at all times observe normal safety regulations. Do not replace components or make adjustments inside the equipment with high voltage turned on. To avoid casualties, always remove power. Shock Hazard Do not attempt to remove the RF transmission line while RF power is present. Do Not Service or Adjust Alone Under no circumstances should any person reach into an enclosure to service or adjust equipment except in the presence of someone who is capable of rendering aid. Safety Earth Ground An uninterruptible safety earth ground must be supplied from the main power source to test instruments. Grounding one conductor of a two conductor power cable is not sufficient protection. Serious injury or death can occur if this grounding is not properly installed. RadioFans.CN 收音机爱 好者资料库 Bird 4304A Thruline Wattmeter ii Resuscitation Personnel working with or near high voltages should be familiar with modern methods of resuscitation. Safety Symbols The caution symbol appears on the equipment indicating there is important information in the instruction manual regarding that particular area. NOTE: Calls attention to supplemental information Warning Statements The following safety warnings appear in the text where there is danger to operating and maintenance personnel, and are repeated here for emphasis. WARNING Warning notes call attention to a procedure, which if not correctly performed, could result in personal injury. CAUTION Caution notes call attention to a procedure, which if not correctly performed, could result in damage to the instrument. WARNING Never attempt to connect or disconnect equipment RF equipment from the transmission line while RF power is being applied. Leaking RF energy is a potential health hazard. iii Caution Statements The following equipment cautions appear in the text whenever the equipment is in danger of damage, and are repeated here for emphasis. WARNING When working with RF powers of 200 watts or more, the potential of the center conductor of the line section will exceed 100 volts. Do not touch the center conductor while RF power is on. CAUTION Do not drop. Calibration could be disturbed or the meter could be damaged as a result. CAUTION Above 800 MHz, do not exceed 150 W RF power. CAUTION RF power must not exceed range switch setting. CAUTION Do not attempt to remove the RF center conductor. This will damage the line section. CAUTION When handling the circuit board, use caution: Do not bend the dc contact finger that extends into the line section. Do not lose the contact finger insulator or the spacers on the mounting screws. Do not disturb the potentiometer settings. Bird 4304A Thruline Wattmeter iv Safety Statements USAGE ANY USE OF THIS INSTRUMENT IN A MANNER NOT SPECIFIED BY THE MANUFACTURER MAY IMPAIR THE INSTRUMENTS SAFETY PROTECTION. USO EL USO DE ESTE INSTRUMENTO DE MANERA NO ESPECIFICADA POR EL FABRICANTE, PUEDE ANULAR LA PROTECCIN DE SEGURIDAD DEL INSTRUMENTO. BENUTZUNG WIRD DAS GERT AUF ANDERE WEISE VERWENDET ALS VOM HERSTELLER BESCHRIEBEN, KANN DIE GERTESICHERHEIT BEEINTRCHTIGT WERDEN. UTILISATION TOUTE UTILISATION DE CET INSTRUMENT QUI NEST PAS EXPLICITEMENT PRVUE PAR LE FABRICANT PEUT ENDOMMAGER LE DISPOSITIF DE PROTECTION DE LINSTRUMENT. IMPIEGO QUALORA QUESTO STRUMENTO VENISSE UTILIZZATO IN MODO DIVERSO DA COME SPECIFICATO DAL PRODUTTORE LA PROZIONE DI SICUREZZA POTREBBE VENIRNE COMPROMESSA. SERVICE SERVICING INSTRUCTIONS ARE FOR USE BY SERVICE - TRAINED PERSONNEL ONLY. TO AVOID DANGEROUS ELECTRIC SHOCK, DO NOT PERFORM ANY SERVICING UNLESS QUALIFIED TO DO SO. SERVICIO v LAS INSTRUCCIONES DE SERVICIO SON PARA USO EXCLUSIVO DEL PERSONAL DE SERVICIO CAPACITADO. PARA EVITAR EL PELIGRO DE DESCARGAS ELCTRICAS, NO REALICE NINGN SERVICIO A MENOS QUE EST CAPACITADO PARA HACERIO. WARTUNG ANWEISUNGEN FR DIE WARTUNG DES GERTES GELTEN NUR FR GESCHULTES FACHPERSONAL. ZUR VERMEIDUNG GEFHRLICHE, ELEKTRISCHE SCHOCKS, SIND WARTUNGSARBEITEN AUSSCHLIELICH VON QUALIFIZIERTEM SERVICEPERSONAL DURCHZUFHREN. ENTRENTIEN LEMPLOI DES INSTRUCTIONS DENTRETIEN DOIT TRE RSERV AU PERSONNEL FORM AUX OPRATIONS DENTRETIEN. POUR PRVENIR UN CHOC LECTRIQUE DANGEREUX, NE PAS EFFECTUER DENTRETIEN SI LON NA PAS T QUALIFI POUR CE FAIRE. RF VOLTAGE MAY BE PRESENT IN RF ELEMENT SOCKET - KEEP ELEMENT IN SOCKET DURING OPERATION. DE LA TENSION H.F. PEAT TRE PRSENTE DANS LA PRISE DE LLMENT H.F. - CONSERVER LLMENT DANS LA PRISE LORS DE LEMPLOI. HF-SPANNUNG KANN IN DER HF-ELEMENT-BUCHSE ANSTEHEN - ELEMENT WHREND DES BETRIEBS EINGESTPSELT LASSEN. PUEDE HABER VOLTAJE RF EN EL ENCHUFE DEL ELEMENTO RF - MANTENGA EL ELEMENTO EN EL ENCHUFE DURANTE LA OPERACION. IL PORTAELEMENTO RF PU PRESENTARE VOLTAGGIO RF - TENERE LELEMENTO NELLA PRESA DURANTE IL FUNZIONAMENTO. Bird 4304A Thruline Wattmeter vi About This Manual This instruction book covers the Bird 4304A RF Thruline Wattmeter. The manual is arranged so that essential safety information appears in the front of the book. Reading the Safety Precautions Section before operating the equipment is strongly advised. The remainder of this Instruction Book is divided into Chapters and Sections. At the beginning of each chapter, a general overview describes the contents of that chapter. Operation First time users should read Chapter 1 Introduction, and Chapter 3 Installation, to get an overview of equipment capabilities and installation. An experienced operator can refer to Chapter 4 Operating Instructions. All instructions necessary to operate the equipment appears in this chapter. Maintenance All personnel should be familiar with the preventive maintenance found in Chapter 5 Maintenance. If a failure should occur, the troubleshooting section will aid in isolating and correcting the cause. Specifications and replacement part lists are also in this chapter. Changes to This Manual We have made every effort to ensure this manual is accurate. If you should discover any errors or if you have suggestions for improving this manual, please send your comment to our factory. This manual may be periodically updated. When inquiring about updates to this manual refer to the part number and revision level on the title page. Table of Contents Safety Precautions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i About This Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3 Travelling Wave Viewpoint. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3 Coupling Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 Load Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 Standing Wave vs. Travelling Wave Viewpoint . . . . . . . . . . . . . . . . .6 vs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Component Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 Impedance Mismatch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11 Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 Connections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 Load Matching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 Operating Instructions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 Normal Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 Low Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 VSWR Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 Cleaning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22 Zero Adjust. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 Connector Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 Element Removal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 Back Cover Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25 Line Section Replacement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25 Meter Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26 Calibration Checks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26 Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28 Customer Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28 Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29 Replacement Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30 Available “QC” Type Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . .31 1 Chapter 1Introduction The Bird 4304A Wattmeter is an in-line sensor that measures RF power and load match in 50 coaxial transmission lines. It can be used with CW, AM, FM, and TV modulation, but not pulse modulation. It is supplied with a special broadband element with a frequency range of 25 to 1000 MHz. It can measure up to 500 W, depending on the frequency, and has a maximum VSWR of 1.07 with the standard “N” connectors. A range switch allows the full scale power to be reduced for greater accuracy. The wattmeter is portable, with an included carrying strap. It has an aluminum housing and an easily removed back cover, with bumpers on the base and back that allow the meter to stand or lie flat. For additional protection, the microammeter is specially shock mounted. A screw on the lower front face of the meter is used to zero the pointer. Below the meter face, the RF line section protrudes slightly from the wattmeter housing with the element socket in the center. The RF line section is precision machined to provide the best possible impedance match to the transmission line under test. A formed phosphor-bronze spring finger protrudes into the element socket to make contact with the element. At each end of the line section are Bird Quick-Change RF connectors that may be interchanged with any other Bird “QC” connector. The wattmeter housing does not interfere with connector changes. Combining the Thruline Wattmeter with a Bird Termaline Load Resistor creates an accurate absorption wattmeter. With this combination, readings only need to be taken in the forward direction because the reflected power will be negligible. Bird 4304A Thruline Wattmeter 2 Figure 1 Bird 4304A Thruline Wattmeter Outline Drawing 5 15 50 150 500 6-7/8” (175 mm) 4” (100 mm) 2-3/8” (59 mm) “QC” CONNECTORS FEMALE N NORMALLY SUPPLIED 4” (100 mm) 1-3/4” (44 mm) POWER RANGE SWITCH ELEMENT 3 Chapter 2Theory of Operation Travelling Wave Viewpoint The easiest way to visualize Thruline operation is from a travelling wave viewpoint. In transmission lines the voltages, currents, standing waves, etc., on any uniform line section result from the interaction of two travelling waves: ! The forward wave (and its power) travels from the source to the load. It has RF voltage Ef and current If in phase, with Ef / If = Zo. ! The reflected wave (and its power) originates by reflection at the load and travels from the load back to the source. It has an RF voltage Er and current Ir in phase, with Er / Ir = Zo. Each wave is mathematically simple and has a constant power: Wf = Watts Forward = Ef2 / Zo = If2 Zo = Ef If Wr = Watts Reflected = Er2 / Zo = Ir2 Zo = Er Ir Zo is the characteristic impedance of a uniform line section. For useful lines it is usually a pure resistance of 50. The RF circuit of the Bird 43 is a length of uniform air line with Zo = 50. Bird 4304A Thruline Wattmeter 4 Coupling Circuit The element, which contains the coupling circuit, and its relationship to the rest of the Bird 4304A is shown in Figure 2. Current is produced in the coupling circuit by travelling waves in the line section, through both inductive and capacitive coupling. The inductive current flows in the direction of the travelling wave, while the capacitive current is independent of the direction of the wave. Therefore, the inductive current produced by one travelling wave will add in phase with the corresponding capacitive current, while that produced by the wave travelling in the opposite direction will subtract. The additive or “arrow” direction is assigned to the forward wave. Figure 2 Thruline Wattmeter Schematic RF Coaxial Line XMTR or LOAD LOAD or XMTR Directional Coupling Detector Element Diode Meter DC Contact Circuit Board Theory of Operation 5 The electrical characteristics of the element are carefully adjusted so that, for the reverse wave, the inductive current will completely cancel the capacitive current, giving a directivity greater than 20 dB. Thus, the element is sensitive at either of its settings, but to only one of the two travelling waves. Thruline Wattmeter measurements are also independent of position along the transmission line. Like similar diode devices, the Bird 4304A indicates the carrier component of amplitude modulation, with very little response to side band components added by modulation. Load Power For loads with a VSWR of 1.2 or less, the power dissipated in a load (Wl) is equivalent (with less than one percent error) to the forward power (Wf). When appreciable power is reflected, as with an antenna, it is necessary to use the exact load power which is given by: Wl = Watts into Load = Wf Wr Good load resistors, such as Bird Termaline loads, will give negligible reflected power. Bird 4304A Thruline Wattmeter 6 Standing Wave vs. Travelling Wave Viewpoint As mentioned previously, the Thruline Wattmeter reacts to forward and reverse travelling waves to measure power in a transmissio