E-mail: support@nautel.com Web: www.nautel.com Nautel Inc.Nautel Limited 201 Target Industrial Circle,10089 Peggys Cove Road, Bangor, MaineUSA04401Hacketts Cove, NS CanadaB3Z 3J 4 Phone: (207) 947-8200Phone: (902) 823-3900 Fax: (207) 947-3693Fax: (902) 823-3183 ISO 9002 RegisteredISO 9001 Registered Copyright 2011 NAUTEL.All rights reserved TECHNICAL INSTRUCTIONS ATU500 LOW POWER AUTOMATIC ANTENNA TUNING UNIT (190 kHz to 1250 kHz and 1600 kHz to 1800 kHz) NAT39D NAPC139C NAPI102A/01 and /02 Original Issue.......................01 March 2011 LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Effective Pages (Page 1) 01 March 2011 LIST OF EFFECTIVE PAGES The list of effective pages lists the status of all pages in this manual. Pages of the original issue are identified by a zero in the Change #column. The change number identifies pages subsequently changed. Blank pages are identified by a -. On a changed page, a vertical bar in the margin opposite the changed material indicates the text affected by the latest change. Original ........................................................01 March 2011 Total number of printed sides in this manual is 73 as listed below: CHANGECHANGECHANGE PAGE#.PAGE#PAGE# Title0 Title (Rear)- Effective (1)0 Effective (2)- Warranty (1)0 Warranty (2)0 Safety (1)0 Safety (2)0 Safety (3)0 Safety (4)- Contents (1)0 Contents (2)0 Contents (3)0 Contents (4)0 1-10 1-20 1-30 1-40 2-10 2-20 2-30 2-40 2-50 2-60 3-10 3-20 3-30 3-40 3-50 3-60 3-70 3-80 4-10 4-20 4-30 4-40 4-50 4-6- 5-10 5-20 5-30 5-40 5-50 5-60 5-70 5-80 5-90 5-100 6-10 6-20 7-10 7-20 7-30 7-40 7-50 7-60 7-70 7-80 7-90 7-100 7-110 7-120 8-10 8-20 9-10 9-2- SD-10 SD-20 SD-3A0 SD-3B0 SD-4A0 SD-4B0 10-10 10-2- MD-10 MD-20 MD-3A0 MD-3B0 MD-40 LOW POWER AUTOMATIC ANTENNA UNIT ATU500 (NAT39D) Warranty (Page 1) 01 March 2011 WARRANTY Nautel Limited/Nautel Maine Incorporated, hereinafter referred to as Nautel, guarantees all mechanical and electrical parts of the equipment for a period of 18 months from date of shipment. 1.A "Part Failure" shall be deemed to have occurred when the part has become defective, or does not have the characteristics required for the specified equipment performance: (a)When the equipment is operated within the design parameters, and (b)When the equipment is installed and adjusted according to Nautel's prescribed procedures as stated in the instruction manual. 2.Nautelshallprovidereplacementsforall"Parts"atnocosttotheCustomerwhentheybecomedefective during the warranty period, and upon the return of the defective part. 3.In the event that a "Part" fails during the warranty period and causes damage to a sub-assembly that cannot be readily repaired in the field, the entire sub-assembly so damaged may be returned to Nautel for repair.The repairs will be made without charge to the Customer. 4.Wherewarrantyreplacementsorrepairareprovidedunderitems2or3,Nautelwillpaythatpartofthe shipping costs incurred in returning the part/assembly to the Customer. 5.Warrantyreplacementpartsandrepair,whichareprovidedunderitems2or3,shallbeguaranteedfora period of ninety days from date of shipment or until the end of the original warranty period, whichever occurs later. 6.Nautel will not assume responsibility for any charges incurred by other than Nautel employees. 7.Nautelshallhavetheprivilegeofinvestigatingwhetherfailureshavebeencausedbyfactorsbeyondits control. 8.Nautel shall in no event be liable for any consequential damages arising from the use of this equipment. 9.When requesting a warranty repair/replacement, please provide complete and accurate information.Observe the instructions regarding 'Equipment Being Returned to Nautel' on page two of this warranty and provide the information requested. 10.When ordering spare/replacement parts; please provide complete and accurate information.Refer to the parts listofthismanualfororderinginformation.Provideasmuchoftheinformationrequestedfor'Equipment BeingReturnedtoNautel'onpagetwoofthiswarrantyasispractical.Theinformationidentifiedbyan asterisk is the minimum required. ON-LINE PART QUOTES Nautel provides an on-line website service (www.nautel.com/in-service.html) where requests for part quotes may be submitted.Requests will normally be responded to within one working day. LOW POWER AUTOMATIC ANTENNA UNIT ATU500 (NAT39D) Warranty (Page 2) 01 March 2011 FACTORY SUPPORT TECHNICAL ASSISTANCE Nautel's field service department provides telephone technical assistance on a 24 hour, seven days a week basis.Requests by other media (facsimile or e-mail) will be responded to the next working day if received after Nautel's normal working hours.Contact the appropriate field service centre from the following: U.S.A. customers use:Nautel IncorporatedTelephone207-947-8200 (24 hours) 201 Target Industrial CircleFacsimile207-947-3693 Bangor, Maine 04401 All other customers use:Nautel LimitedTelephone902-823-3900 (24 hours) 10089 Peggys Cove Road,Facsimile902-823-3183 Nova Scotia, Canada E-Mailsupport@nautel.com B3Z 3J 4Webwww.nautel.com MODULE EXCHANGE SERVICE In order to provide Nautel customers with a fast and efficient service in the event of a problem, Nautel operates a factory rebuilt, module exchange service which takes full advantage of the high degree of module redundancy in Nautelequipment.ThismoduleexchangeserviceisoperatedfromNautelsfactoryinBangor,Maineand Hacketts Cove, Nova Scotia.These two locations allow us to provide a quick turn around service to keep our customersontheair.Duringthetransmitterswarrantyperiod,upto18monthsfromshipment,repairand exchange of modules is at no charge to the customer.When the warranty has expired, a charge of 80% of the list price for all exchanged modules is made.If the faulty module is returned to Nautel within 30 days, a credit is issued reducing this charge by one half to 40% of the list price.U.S.A. customers are required to contact our Bangor, Maine facility.Canadian and overseas customers should contact our Nova Scotia, Canada facility. EQUIPMENT BEING RETURNED TO NAUTEL All equipment being returned to Nautel and all requests for repairs or replacements should be marked 'field return' and addressed to the appropriate Nautel facility. Completeandaccurateinformationregardingtheequipmentbeingreturnedwillensurepromptattention and will expeditethedispatchofreplacements.Refertothenameplateonthetransmitterand/ortheappropriate module/assembly to obtain name, type, part and serial number information.Refer to the parts list of this manual or the appropriate service instruction manual for additional ordering information. The following information should accompany each request: *Model of Equipment *Serial number of Equipment *Name of Part/Assembly Serial number of Part/Assembly *Complete reference designation of Part/Assembly *Nautel's part number of Part/Assembly *OEM's part number of Part/Assembly Number of hours in Use Nature of defect *Return shipping address *Denotes minimum information required to order spare/replacement parts LOW POWER AUTOMATIC ANTENNA UNIT ATU500 (NAT39D) Safety (Page 1) 01 March 2011 ARTIFICIAL RESPIRATION (MOUTH-TO-MOUTH) (a)START MOUTH-TO-MOUTH BREATHING IMMEDIATELY. SECONDS COUNT.Do not wait to loosen clothing, warm the casualty, or apply stimulants. (b)ASSESS RESPONSIVENESS OF CASUALTY.Do not jar casualty or cause further physical injury (Figure 1) (c)IF POSSIBLE, SEND A BYSTANDER TO GET MEDICAL HELP.Do not leave casualty unattended (Figure 2) (d)CHECK CAROTID PULSE (Figure 3) (e)LAY CASUALTY ON HIS/HER BACK and place any available jacket or blanket under his/her shoulders. (f)TILT THE HEAD BACK AND LIFT THE CHIN to open the airway (Figure 4) (g)PINCH CASUALTYS NOSE AND EXHALE TWO SLOW BREATHS INTO CASUALTY (Figure 5) (h)REMOVE YOUR MOUTH and check for breathing (Figure 6) (i)CONTINUE GIVING ONE BREATH EVERY FIVE SECONDS without interruption.If any air is retained in the stomach after exhalation by casualty, press gently on stomach to expel air. (j)IF CHEST DOES NOT RISE CHECK for obstruction in casualtys mouth: clear foreign material using your finger, tissues, etc.Use chin lift and recommence mouth-to-mouth breathing. (k)WHILE MOUTH-TO-MOUTH BREATHING IS CONTINUED have someone else: (a)Loosen casualtys clothing. (b)Keep the casualty warm. (l)DONT GIVE UP.Continue without interruption until the casualty is revived, or until a doctor pronounces the casualty dead.Four hours or more may be required. (m)DO NOT PROVIDE ANYTHING ORALLY while victim is unconscious. 1 2 3 4 5 6 LOW POWER AUTOMATIC ANTENNA UNIT ATU500 (NAT39D) Safety (Page 2) 01 March 2011 GENERAL RULES FOR TREATMENT FOR BURNS, BLEEDING, AND SHOCK 1.After casualty has revived, treat for injuries and shock. 2.Reassure casualty. 3.Try to make him comfortable. 4.Keep him reasonably warm but do not apply heat. 5.If thirsty, liquids may be given but no alcohol (no liquids should be given in cases of severe burns). 6.Treat burns or wounds.Infection danger in treating burns or wounds is very great so ensure hands are clean and do not handle affected areas more than necessary. 7.Do not apply salves, grease, etc. to burns. 8.Do not remove burned clothing which adheres to the skin or break blisters. 9.Cover the burn with a dry sterile dressing, piece of sheeting, etc. 10.Bandage lightly over blisters where care must be taken to cover and not to break. 11.If severe bleeding of wound, elevate affected area, except in the case of a fracture. 12.Expose wound and apply pressure. 13.Apply dressing, pad and bandage. 14.Forburnsandbleeding,immobilizeinjuredpartusingsplintsifnecessaryandkeeppatientinrestful position during removal to hospital or expert medical attention. 15.In all cases, send for medical aid immediately. LOW POWER AUTOMATIC ANTENNA UNIT ATU500 (NAT39D) Safety (Page 3) 01 March 2011 ELECTRIC SHOCK - RESCUE METHODS Electricity can damage the body in a number of ways.It may interfere with the proper functioning of the nervous system and the heart action, it can subject the body to extreme heat and can cause severe muscular contractions.The path that the current of electricity takes through the body is important.Currents which pass from hand to hand or from hand to foot may pass directly through the heart and upset its normal functioning.This threat to life is related to the amount of current or amperage that will flow through a victim's body.Very little current (as little as 10 milliamps) can result in severe shock or death. Speed in the application of first aid measures is absolutely essential in cases of electrical injury.As soon as the victim isfreedsafelyfromthesourceoftheelectricalcurrent,ifbreathinghasstopped,artificialrespirationshouldbe commencedimmediately.Ifthecarotidpulsecannotbefelt,externalcardiacmassageshouldbecommenced simultaneously.Resuscitationshouldbecontinueduntilthepatientisbreathingonhisownoruntilmedicalaid arrives.Survival rates can be quite high if cardio-pulmonary resuscitation is started within 3 to 4 minutes of the injury being received. ACT AT ONCE - DELAY OR INDECISION MAY BE FATAL 1.Turn OFF the electrical source. 2.Commence artificial respiration immediately. 3.Treat for burns, bleeding and shock. REMOVING A CASUALTY FROM ELECTRICAL CONTACT LOW VOLTAGE - 0 to 240 volts (household use) Switch off the current, if possible and time permits.If the switch cannot be located immediately and the supply is throughaflexiblecordorcable,thecurrentmaybeshutoffbyremovingtheplugorevenbreakingthecableor wrenching free.Never attempt to shut off current by cutting cord with a knife or scissors. If the current cannot be shut off, the greatest care is necessary in removing the casualty.Household rubber gloves, rubber or plastic hose (if there is no water in them), a dry unpainted stick or a clean dry rope can be used to free victim. HIGH VOLTAGE - 240 volts and up (industrial machines and power lines) Do not touch any person or equipment in contact with a wire. Use a dry unpainted pole, clean dry rope, dry rubber or plastic water hose to separate the casualty from the contact. Keep as far away as possible. Do not touch the casualty until he is free. LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Contents (Page 1) 01 March 2011 TABLE OF CONTENTS Section Page 1GENERAL INFORMATION 1.1INTRODUCTION.............................................................................................................................1-1 1.2PURPOSE AND SCOPE OF MANUAL ..........................................................................................1-1 1.3PURPOSE OF EQUIPMENT..........................................................................................................1-1 1.4FACTORY REPAIR SERVICE.......................................................................................................1-1 1.5MECHANICAL DESCRIPTION.......................................................................................................1-1 1.5.1CABINET...........................................................................................................................................1-1 1.5.2REMOVABLE PWB/CHASSIS.........................................................................................................1-1 1.5.3ATU CONTROL/MONITOR PWB....................................................................................................1-3 1.5.4VECTOR SERIAL INTERFACE PWB..............................................................................................1-3 1.5.5LOADING COIL ASSEMBLY..........................................................................................................1-3 1.6TECHNICAL SUMMARY................................................................................................................1-3 1.7SPECIAL TOOLS AND TEST EQUIPMENT.................................................................................1-3 2THEORY OF OPERATION 2.1GENERAL.........................................................................................................................................2-1 2.2ANTENNA TUNING UNIT OVERVIEW...........................................................................................2-1 2.3ATU CONTROL/MONITOR PWB OVERVIEW..............................................................................2-1 2.3.1SERVO PROBE................................................................................................................................2-1 2.3.2FORWARD/REFLECTED POWER PROBE ...................................................................................2-1 2.3.3MATCHING TRANSFORMER/CURRENT PROBE........................................................................2-1 2.3.4TUNING COILS ................................................................................................................................2-1 2.3.5AUTOMATIC TUNING SELECTOR.................................................................................................2-1 2.3.6TUNING DRIVE MOTOR .................................................................................................................2-1 2.4VECTOR SERIAL INTERFACE PWB OVERVIEW........................................................................2-2 2.4.1POWER SUPPLIES..........................................................................................................................2-2 2.4.2SERVO PROBE................................................................................................................................2-2 2.4.3INPUT VOLTAGE AND CURRENT PROBES ................................................................................2-2 2.4.4MICROCONTROLLER.....................................................................................................................2-2 2.4.5ANTENNA CURRENT PROBE........................................................................................................2-2 2.5ATU CONTROL/MONITOR PWB DETAILED CIRCUIT DESCRIPTION....................................2-2 2.5.1SERVO PROBE................................................................................................................................2-2 2.5.2MOTOR LIMIT CONTROL..............................................................................................................2-3 2.5.3FORWARD/REFLECTED POWER PROBE ...................................................................................2-4 2.5.4MATCHING TRANSFORMER/CURRENT PROBE........................................................................2-4 2.6VECTOR SERIAL INTERFACE PWB DETAILED CIRCUIT DESCRIPTION...............................2-4 2.6.1SERVO PROBE................................................................................................................................2-4 2.6.2POWER SUPPLIES..........................................................................................................................2-5 2.6.3CURRENT/VOLTAGE SAMPLES ...................................................................................................2-5 2.6.4ANTENNA CURRENT PROBE........................................................................................................2-5 2.6.5MICROCONTROLLER.....................................................................................................................2-5 2.6.5.1Analog Inputs .................................................................................................................................2-5 2.6.5.2Digital Inputs..................................................................................................................................2-6 2.6.5.3Digital Outputs...............................................................................................................................2-6 2.6.6SERIAL COMMUNICATION (RS485)..............................................................................................2-6 LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Contents (Page 2) 01 March 2011 TABLE OF CONTENTS (Continued) SectionPage 3 - INSTALLATION AND PREPARATION FOR USE 3.1GENERAL.........................................................................................................................................3-1 3.2TEST EQUIPMENT..........................................................................................................................3-1 3.3SITE REQUIREMENTS ...................................................................................................................3-1 3.3.1PROXIMITY TO TRANSMITTER.....................................................................................................3-1 3.3.2ANTENNA STRUCTURE ................................................................................................................3-1 3.3.3ANTENNA FEED RF CABLE ..........................................................................................................3-1 3.3.4EXTERNAL CABLING......................................................................................................................3-1 3.3.5RF TRANSMISSION LINE ...............................................................................................................3-1 3.3.6DC POWER CABLE.........................................................................................................................3-1 3.3.7REMOTE CONTROL/MONITOR WIRING......................................................................................3-2 3.3.8GROUNDING....................................................................................................................................3-2 3.4UNPACKING...................................................................................................................................3-3 3.5ANCILLARY PARTS........................................................................................................................3-4 3.6USER SUPPLIED PARTS...............................................................................................................3-4 3.7USER DETERMINED INFORMATION............................................................................................3-5 3.7.1CARRIER FREQUENCY .................................................................................................................3-5 3.7.2ANTENNA CAPACITANCE..............................................................................................................3-5 3.7.3ANTENNA SERIES RESISTANCE .................................................................................................3-5 3.8PRE-INSTALLATION REQUIREMENTS...........................................................................................3-5 3.8.1TUNING COIL PRE-INSTALLATION............................................................................................3-5 3.8.1.1Tuning Coils ...................................................................................................................................3-5 3.8.1.2Selecting Tuning Coil Taps...........................................................................................................3-5 3.8.2ATU CONTROL/MONITOR PWB PANEL PRE-INSTALLATION.......................................................3-7 3.8.3SPARK GAP PRE-INSTALLATION .....................................................................................................3-7 3.9EXTERNAL CABLE CONNECTIONS.................................................................................................3-7 3.10PLACING ATU IN SERVICE................................................................................................................3-7 4OPERATING INSTRUCTIONS 4.1 GENERAL .............................................................................................................................................4-1 4.2 EMERGENCY SHUTDOWN.................................................................................................................4-1 4.3 CONTROLS AND INDICATORS .........................................................................................................4-1 4.3.1READING REFLECTED POWER ........................................................................................................4-1 4.4 PRESTART-UP CHECKS ....................................................................................................................4-1 4.5 OPERATING PROCEDURES.............................................................................................................4-1 4.6 SETTINGS FOR UNATTENDED OPERATION.................................................................................4-1 4.7 PLACING ATU IN UNATTENDED OPERATION................................................................................4-2 LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Contents (Page 3) 01 March 2011 TABLE OF CONTENTS (Continued) SectionPage 5CALIBRATION AND TESTING 5.1 GENERAL .............................................................................................................................................5-1 5.2 CALIBRATION TEST EQUIPMENT ....................................................................................................5-1 5.3 OPERATION OF EQUIPMENT............................................................................................................5-1 5.4 CALIBRATION PROCEDURES...........................................................................................................5-1 5.4.1INITIAL CONTROL SETTINGS ............................................................................................................5-1 5.4.2INITIAL TURN-ON.................................................................................................................................5-1 5.4.3MANUAL CHECK OF TUNING DRIVE................................................................................................5-2 5.4.4INITIAL CHECK OF RF TUNING AND AUTOMATIC OPERATION...................................................5-2 5.4.4.1Automatic Control Assumed...........................................................................................................5-3 5.4.4.2Automatic Control Not Assumed....................................................................................................5-3 5.4.5FINAL TUNING OF RF CIRCUITS.......................................................................................................5-4 5.4.6RF POWER INDICATION.....................................................................................................................5-5 5.4.7SPARK GAP ALIGNMENT ...................................................................................................................5-5 5.4.8IMPROVING MODULATION DEPTH ON RF OUTPUT......................................................................5-8 5.4.9CALIBRATING ANTENNA CURRENT.................................................................................................5-8 5.5FUNCTIONAL TEST PROCEDURES..................................................................................................5-9 5.6POST-TESTING PROCEDURES...................................................................................................... 5-10 6MAINTENANCE 6.1GENERAL. ............................................................................................................................................6-1 6.2MAINTENANCE AIDS.........................................................................................................................6-1 6.2.1PARTS INFORMATION........................................................................................................................6-1 6.2.2WIRING INFORMATION.......................................................................................................................6-1 6.2.3ELECTRICAL SCHEMATIC..................................................................................................................6-1 6.2.4MECHANICAL DRAWINGS .................................................................................................................6-1 6.3SCHEDULED MAINTENANCE............................................................................................................6-1 6.4CORRECTIVE MAINTENANCE...........................................................................................................6-1 6.5FRONT COVER WEATHER SEAL......................................................................................................6-1 6.6TUNING COIL REPLACEMENT..........................................................................................................6-1 7PARTS LIST 7.1INTRODUCTION...................................................................................................................................7-1 7.2REFERENCE DESIGNATION LISTS.................................................................................................7-1 7.3COLUMN CONTENT EXPLANATION ................................................................................................7-1 7.3.1REF DES COLUMN.............................................................................................................................7-1 7.3.2DESCRIPTION COLUMN.....................................................................................................................7-1 7.3.3NAUTEL #COLUMN ............................................................................................................................7-1 7.3.4VENDOR #COLUMN...........................................................................................................................7-1 7.3.5OEM CODE COLUMN..........................................................................................................................7-1 7.4OEM CODE TO MANUFACTURER CROSS-REFERENCE .............................................................7-2 7.4.1MANUFACTURERS INDEX.................................................................................................................7-2 7.5COMMON ABBREVIATIONS / ACRONYMS .....................................................................................7-2 8 - WIRING INFORMATION 8.1INTRODUCTION...................................................................................................................................8-1 8.2WIRING LISTS NOT PROVIDED.........................................................................................................8-1 8.3PRINTED WIRING PATTERNS...........................................................................................................8-1 8.4WIRE COLORS.....................................................................................................................................8-1 8.5WIRING LISTS PROVIDED..................................................................................................................8-1 LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Contents (Page 4) 01 March 2011 TABLE OF CONTENTS (Continued) SectionPage 9 - ELECTRICAL SCHEMATICS 9.1INTRODUCTION...................................................................................................................................9-1 9.2COMPONENT VALUES.......................................................................................................................9-1 9.3GRAPHIC SYMBOLS...........................................................................................................................9-1 9.4LOGIC SYMBOLS ................................................................................................................................9-1 9.5REFERENCE DESIGNATIONS...........................................................................................................9-1 9.6LOCATING LOGIC/SCHEMATIC DIAGRAMS...................................................................................9-1 10 - MECHANICAL DRAWINGS 10.1INTRODUCTION................................................................................................................................ 10-1 10.2LOCATING ASSEMBLY DETAIL DRAWINGS............................................................................... 10-1 10.3CONTENT OF MECHANICAL DRAWINGS..................................................................................... 10-1 LIST OF ILLUSTRATIONS NumberTitlePage 1-1ATU500 Automatic Antenna Tuning Unit..................................................................................................1-2 3-1Typical Site Layout......................................................................................................................................3-2 3-2Typical Downlead Insulator Installation......................................................................................................3-3 3-3Tuning Coil Tap Configurations ..................................................................................................................3-8 5-1Spark Gap Detail........................................................................................................................................5-7 5-2Peak Antenna Voltage Versus Spark Gap Setting ....................................................................................5-7 SD-1Block Diagram - Automatic Antenna Tuning Unit (NAT39D) .................................................................SD-1 SD-2Electrical Schematic - Automatic Antenna Tuning Unit (NAT39D w/ NAPC139C)................................SD-2 SD-3AElectrical Schematic Vector Serial Interface PWB (NAPI102A/01) (Sheet 1 of 2)........................... SD-3A SD-3BElectrical Schematic Vector Serial Interface PWB (NAPI102A/02) (Sheet 1 of 2)........................... SD-3B SD-4AElectrical Schematic Vector Serial Interface PWB (NAPI102A/01) (Sheet 2 of 2)........................... SD-4A SD-4BElectrical Schematic Vector Serial Interface PWB (NAPI102A/02) (Sheet 2 of 2)........................... SD-4B MD-1Assembly Detail ATU500 (NAT39D) Automatic Antenna Tuning Unit............................................... MD-1 MD-2Assembly Detail NAPC139C ATU Control/Monitor PWB................................................................... MD-2 MD-3AAssembly Detail NAPI102A/01 Vector Serial Interface PWB...........................................................MD-3A MD-3BAssembly Detail NAPI102A/02 Vector Serial Interface PWB...........................................................MD-3B MD-4Dimensional Information ATU500 (NAT39D) Automatic Antenna Tuning Unit.................................. MD-4 LIST OF TABLES NumberTitlePage 1-1Test Equipment ...............................................................................................................................................1-4 3-1Tuning Coil Inductance Values (uH)..............................................................................................................3-4 3-2Tuning Coil Series Loss Resistance (Ohms) .................................................................................................3-6 3-3Selecting Matching Transformer Input/Output Taps.......................................................................................3-6 4-1Antenna Tuning Unit Controls and Indicators.................................................................................................4-3 5-1Antenna Reactance - Xa (Ohms) ...................................................................................................................5-6 6-1Troubleshooting Assistance Chart..................................................................................................................6-2 7-1Manufacturers' Index.......................................................................................................................................7-2 8-1Wiring Lists Provided ......................................................................................................................................8-1 8-2Wiring List NAT39D Automatic Antenna Tuning Unit .................................................................................8-2 9-1List of Electrical Schematics ...........................................................................................................................9-1 10-1List of Mechanical Drawings .........................................................................................................................10-1 LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Page 1-1 01 March 2011 SECTION 1 GENERAL INFORMATION INTRODUCTION 1.1The subject automatic antenna tuning unit (ATU)isanautomatictuningdevicethatprovides impedance matching between a 50-ohm feeder cable fromatransmitterandanantenna.Nautel's nomenclature control number is NAT39D. The ATU is referenced as the NAT39D throughout this manual. TheATUoperatesintheLF/MFband(190to 1800 kHz).Provisionismadeforlocalandremote manualtuningandfortransmittertoATU intercommunications. PURPOSE AND SCOPE OF MANUAL 1.2Thismanualprovidestheinformation necessarytoinstall,operateandmaintainNautel's NAT39 - antenna tuning units (see figure 1-1).Other configurations, not specifically covered in this manual are available on request. PURPOSE OF EQUIPMENT 1.3The subject ATU interfaces and impedance matches the RF output of a low power transmitter to anantenna.Aservomechanismautomatically maintainsatunedconditionwhentheantenna reactancechangesbecauseofenvironmental conditions.Thetransmitter'sRFoutputlevel (unmodulatedRFcarrier)mustfallbetween25and 125 W at an output impedance of 50 . The antenna must have a capacitance of between 250 and 1250 pF andaseries(total)resistanceofbetween3.7and 60.5 . FACTORY REPAIR SERVICE 1.4Nautelprovidesafactorymodulerepair service for users of Nautel's equipment. Users who do not have repair facilities or who are not able to repair an assembly may utilize this service for a nominal fee. Refer to warranty (page 2) for address of Nautel repair facility and information to be supplied with returned parts. MECHANICAL DESCRIPTION 1.5Each automatic ATU is housed in an IP66 rated,all-weathercabinetforoutdoorinstallation closetotheantenna.Electricalinterconnectionis made via cables that enter the cabinet through a sealed connector in the side. The dc input and control power wiring is terminated on terminal blocks of the ATU control/monitor PWB (A1) and Vector serial interface PWB (A2) that are located behind the cabinets front cover. 1.5.1CABINET:RefertofigureMD-1.The cabinet is assembled from heavy gauge metal and is standardfittedforrearmounting.Abase-mounting optionisalsoavailable.Accesstothecabinetis achieved by removing the weather-tight, front panel. Provision for an air intake, plugged during shipping, is provided at the base of the cabinet. Depending on environmental conditions (i.e., condensation), the user may wish to remove the plugging hardware and install asuitablemicro-filter.Theairintakemustnotbe obstructedwhentheunitisinstalled.Thecabinet contains a loading coil assembly, a lightning arrestor sparkgap,aninsulatedRFfeed-through/connector, andaremovablePWB/chassisthatcontainsthe electronic circuitry. The electrical wiring access hole isfittedwithaliquid-tightconnector,whichis tightened (sealed) after wiring is installed, to ensure rodents, dirt and moisture do not enter the cabinet. 1.5.2REMOVABLEPWB/CHASSIS:Refer to figure MD-1. The removable PWB/chassis consists of a fabricated metal panel that is used to support the ATUcontrol/monitorPWB(A1)andVectorserial interfacePWB(A2).Itmayberemovedbyfirst removing serial interface PWB A2 and its wiring and mountingpanel,andthenunfasteningfourcaptive screwfasteners,disconnectingtheinterconnecting wiring and carefully extracting it from the cabinet. It contains the electrical monitoring and control circuitry for the ATU. LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Page 1-2 01 March 2011 Figure 1-1ATU500 Automatic Antenna Tuning Unit LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Page 1-3 01 March 2011 1.5.3ATUCONTROL/MONITORPWB: TheATUcontrol/monitorPWB(A1)containsthe operatingandtestcontrolsandindicators,which consist of a power/current meter, rocker switches that selectPOWERON/OFF,AUTOON/OFF,INDUCTANCE INCREASE/DECREASEandvariousmetering parameters.Allelectricalconnectionsaremadevia spadeterminalsat15-positionterminalblocksTB1 and TB2. 1.5.4VECTOR SERIAL INTERFACE PWB (OPTIONAL): The Vector serial interface PWB (A2) providesameansofcommunicationswithan associated Vector transmitter. It contains test controls and indicators, which consist of push-button switches thatselectXMTROFF,LOCAL/REMOTE,INCRLandDECRL, and INHBLTUNE. All electrical connections aremadeviaspadeterminalsat6-positionterminal block TB1 and via discrete wiring at 6 and 9 position terminal blocks TB2 and TB3. 1.5.5LOADINGCOILASSEMBLY: Refer to figure MD-1. The loading coil assembly consists of a two-coildrivemechanismthatmovesaboutafixed ferrite core. The loading coils, each with three taps, may be connected in series or in parallel.The taps provide fixed, inductance range selections, while the coilsaremechanicallydrivenaboutafixed,ferrite core to fine-tune the coils to the required inductance. 1.5.5.1Theinstalledloadingcoilsareselected from one of two options: a high inductance set or a lowinductanceset.Thehighinductancesetis normallyinstalledsinceitsinductancerange accommodatesthevastmajorityofantenna capacitance/carrier frequency combinations. The low inductancesetisinstalled,inlieuofthehigh inductanceset,onlywhenspecificallyrequestedat time of purchase. Low inductance coils will be used forhigh-endcarrierfrequencyapplications(above 1600 kHz). Refer to paragraph 3.8.1.1 for additional loading (tuning) coil configuration. 1.5.5.2Theloadingcoilsareinstalledona threaded rod that forms part of a motor driven gear train.Thegeartrainislimitedinitstravelbylimit detectors at the upper and lower extremities. TECHNICAL SUMMARY 1.6A Technical Summary is provided at in the specifications brochure at the front of this manual. SPECIAL TOOLS AND TEST EQUIPMENT 1.7There are no special tools required. Table 1-1 - Test Equipment, lists the test equipment that is required to operate and maintain the subject ATU. LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Page 1-4 01 March 2011 Table 1-1: Test Equipment PART, MODEL, OR TYPE NUMBER NOMENCLATURE(EQUIVALENTS MAY BE USED)APPLICATION AC VoltmeterHP400EPrecise measurement of RF voltage during calibration and trouble Digital VoltmeterAny good quality 3 1/2 digit digital voltmeterMeasure voltages and resistances during testing and troubleshooting procedures. ** Dummy LoadResistive 50-ohm dummy load rated at 250 watts (twice the maximum power rating of the associated transmitter). Provides precise 50-ohm load during calibration and troubleshooting OscilloscopeAny good quality oscilloscope Monitor waveforms during testing and trouble shooting procedures. ** - Denotes may be simulated (with limited modulation/capability) using resistors provided in ATU LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Page 2-1 01 March 2011 SECTION 2 THEORY OF OPERATION GENERAL 2.1Thetheoryofoperationfortheantenna tuning unit (ATU) is presented in this section. ANTENNA TUNING UNIT OVERVIEW 2.2SeeblockdiagraminfigureSD-1.The ATU is an integral part of a radio beacon transmitter systemoperatingintheLF/MFband(190kHzto 1800 kHz).It interfaces a beacon transmitter, such as theNautelND500orVR125,toanantennaand maintainstheantennaimpedance,asseenbythe transmitter, at 50 ohms under changing environmental conditions.Provisionismadetomanuallytunethe tuning unit locally and remotely from the transmitter location,andforintercommunicationsbetweenthe ATU and the transmitter site. The dc supply voltage requiredbytheATU(+15Vor+24V)mustbe provided by the associated transmitter. ATU CONTROL/MONITOR PWB OVERVIEW 2.3SeeblockdiagraminfigureSD-1.With the exception of the tuning coils (L1 and L2) and the tuningdrivemotor(B1),allcircuitrydescribedin thefollowingparagraphsislocatedontheATU control/monitorPWB(A1)ortheVectorserial interface PWB (A2). Refer to the paragraph heading to determine whether it describes A1 or A2. 2.3.1SERVOPROBE:Theservoprobe monitors the RF input for voltage and current phase relationship. When the load impedance is resistive, the voltage and current are in phase and the servo probe will not produce an output. When the load impedance is inductive or capacitive, the voltage and current will not be in phase. The servo probe will then produce an auto increase signal if more inductance is required or an auto decrease signal if less inductance is required. The servo probe's monitoring circuits are inhibited by theapplicationofaservoinhibitsignalfromthe transmitterwhentheATUisbeingtunedmanually fromthetransmittersiteorfromaremotelocation. The output of the servo probe will then be overridden bytheincreaseordecreasesignalfromthe transmitter. 2.3.2FORWARD/REFLECTEDPOWER PROBE: The forward/reflected power probe samples theRFsignalandproducesoutputsthatare representative of the forward power and the reflected power.Theseoutputs,asselectedbyFWD/REFLD switch S3, can be displayed on the RF WATTS scale of meter M1. 2.3.3MATCHINGTRANSFORMER/ CURRENTPROBE: The matching transformer is a widebandautomatchingtransformerwhich transformsthesumofthecoillossresistanceand antennaseriesresistanceonitsoutputtoa50ohm impedance at its input. Selective taps provide a wide selectionoftransformerratiostomatchaload resistanceof3.7to60.5ohms.Thecurrentprobe constantlysamplestheRFoutputandproducesa signalthatisrepresentativeofthemeanantenna current.This signal is applied to switch S7 and can be displayed on the RF AMPERES scale of meter M1. 2.3.4TUNINGCOILS:Thetuningcoilstune theantennatotheoperatingfrequencyofthe transmitter.Therearetwotuningcoils,which, dependingonthefrequency,maybeconnectedin parallel or in series. Coarse tuning is provided using selectivetapsoneachcoil.Finetuningis accomplished by altering the position of tuning coil using a reversible motor. 2.3.5AUTOMATICTUNINGSELECTOR: The automatic tuning selector comprises two switches that determine where the control signal for the tuning drivemotorwilloriginate.Normallytheautomatic output of the servo probe is selected. 2.3.6TUNINGDRIVEMOTOR:Thetuning drivemotorisareversibledcmotorthatdrivesa mechanism to position the coils about a fixed ferrite core.Limitdetectorsinhibitthemotorselectrical circuit if an end of travel condition is obtained. LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Page 2-2 01 March 2011 VECTORSERIALINTERFACEPWB OVERVIEW 2.4SeeblockdiagraminfigureSD-1.The VectorserialinterfacePWB(A2)isanoptional board that can be used when the ATU500 is paired with a Vector transmitter. It contains a servo probe, currentprobe,tuningdrivecircuitry(forthe inductiveterm),powersupplies,localcontrols, alarm and status LEDs and microcontroller control. All circuitry described in the following paragraphs is located on the Vector serial interface PWB (A2). 2.4.1POWERSUPPLIES:Thedcpower sourceisregulatedto+15VtosupplytheATU control/monitorPWBandto+5Vtopowerthe microcontrollerandothercontrolcircuitryonthe PWB. 2.4.2SERVOPROBE:Theservoprobe monitors the RF input for voltage and current phase relationship. When the load impedance is resistive, the voltage and current are in phase and the servo probe will not produce an output. When the load impedance is inductive or capacitive, the voltage and current will not be in phase. The servo probe will then produce an increaseLsignal if more inductance is required or adecreaseLsignal if less inductance is required. The information from the servo probe signals is fed to the microcontroller which controls the inductive motor. 2.4.3INPUTVOLTAGEANDCURRENT PROBES: Samples of the input voltage and current, whichareusedtodeterminetheATU500sinput resistance, are applied to the microcontroller. 2.4.4MICROCONTROLLER:Themicro-controller generates status and alarms. It also provides aserialdataconnectionwhichcanberemotely monitoredforATUstatusinformationandRF antenna current level. 2.4.5ANTENNACURRENTPROBE:The antennacurrentprobeconstantlysamplestheRF output and produces a signal that is representative of the mean antenna current. A sample of the antenna current is applied to the microcontroller. ATUCONTROL/MONITORPWBDETAILED CIRCUIT DESCRIPTION2.5The following descriptions provide a reader withanin-depthunderstandingofcomplexornon-obvious circuit functions. The descriptions are keyed totheblockdiagramSD-1andexpandonthe associated descriptions. Partial reference designations aregiveninthefollowingdescriptions.Unless otherwise specified, all reference designations in the following paragraphs are part of ATU control/monitor PWB A1 (see electrical schematic SD-2). 2.5.1SERVOPROBE:TransformerT1 transforms the RF current passing through the primary winding to the secondary windings.Since the eight-turnsecondarywindingofT1areidentical,theRF currentflowingineachwillbeinphase.Diode bridges CR2 through CR5 and CR6 through CR9 act as RF switches.They are alternately switched on and off, one by the positive half cycle and the other by the negative half cycle, of the RF current. The 50-ohm RF voltage signal is applied to both diode bridges after being phase-shifted ninety degrees by capacitor C5. 2.5.1.1If this voltage is exactly ninety degrees out ofphasewiththecurrentflowingintheeight-turn secondaries of transformer T1, the net dc potential, at the output of both diode bridges will be zero, since bothwillgateequalportionsofthenegativeand positive half cycles. In this state, Q3 and Q4 are not forwardbiasedandtheyarebothturnedoff.Transistors Q5 and Q6 are both forward biased, but becausetheiremittersareatthesamepotential, current will not flow through off-board tuning drive motor B1. 2.5.1.2If the voltage from C5 is not exactly ninety degrees out of phase with the current flowing in the eight-turn secondaries of transformer T1, the net DC outputwillbepositivefromonediodebridgeand negative from the other. LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Page 2-3 01 March 2011 2.5.1.3If the output of diode bridge CR2 through CR5goespositive,transistorQ3willbeforward biased and turn on.The junction of diode CR16 and resistorsR14andR16willgotogroundpotential, reverse biasing transistor Q5.Q5 will be turned off.Simultaneously,theoutputofdiodebridgeCR6 through CR9 will go negative, transistor Q4 will still bereversebiased,maintainingtheforwardbiason transistor Q6. A current path, from +15 V to ground, will be established between transistors Q6 and Q3, via normallyclosedcontactsS4-4/S4-5andS5-1/S5-2, off-boardtuningdrivemotorB1,normallyclosed contactsS5-5/S5-4andS4-2/S4-1anddiodeCR16. The off-board tuning drive motor will drive the coils upward(directionrequiredtoincreasecoil inductance). 2.5.1.4If the output of diode bridge CR6 through CR9goespositive,transistorQ4willbeforward biased and turn on.The junction of diode CR17 and resistorsR15andR17willgotogroundpotential, reverse biasing transistor Q6.Q6 will be turned off.Simultaneously,theoutputofdiodebridgeCR2 through CR5 will go negative, transistor Q3 will still bereversebiased,maintainingtheforwardbiason transistor Q5.A current path, from +15V to ground, will be established between transistors Q5 and Q4, via normallyclosedcontactsS4-1/S4-2andS5-4/S5-5, off-boardtuningdrivemotorB1,normallyclosed contactsS5-2/S5-1andS4-5/S4-4anddiodeCR17. The tuning drive motor will drive the coils downward (direction required to decrease coil inductance). 2.5.1.5ResistorR1anddiodesCR1andCR24 form a voltage divider that maintains a 1.4V bias, that acts as a pedestal, to aid in turning on transistor Q3 or Q4, since they are both Darlington transistor pairs and would normally require 1.4V forward bias to turn on. 2.5.1.6Theoutputoftheservoprobemaybe controlled manually from the transmitter site or from a remotelocation.Whentheservooutputisbeing manually controlled from the ATUs front panel, the AUTO switch (S2) should be set to OFF.The AUTO lamp (DS2) should turn off.When the servo output is being manually controlled from a remote location, a 12Vservoinhibitsignal(fromtheassociated transmitter)willforwardbiastransistorQ2.Transistor Q2 will turn on and place the junction of diodesCR14andCR15atgroundpotential, effectively shorting the output of the diode bridges to ground and inhibiting the normal servo tuning action. IfagroundisappliedtoTB1-3asanincrease command,transistorQ6willbereversebiasedand current will flow as described in paragraph 2.5.1.4.If a ground is applied to TB1-4 as a decrease command, transistor Q5 will be reverse biased and current will flow as described in paragraph 2.5.1.3. 2.5.2MOTORLIMITCONTROL:Themotor limitcontrolcircuitryconsistsofphoto-interrupter devicesU1andU2,transistorsQ7throughQ10,a mechanical travel indicator (indicative of position of movabletuningcoilsL1andL2)andassociated components.Photo-interrupters U1 and U2 act as the upper and lower limit detectors. 2.5.2.1When tuning coils L1 and L2 are between theirupperandlowerlimits,themechanicaltravel indicator does not obstruct the light-source path of U1 and U2 and they will turn on.Transistors Q7 and Q8, connectedascurrentamplifiers,willturnon.Darlingtontransistors Q9 and Q10 will turn on and +15V will be applied as the +15V-A (E1) and +15V-B (E2) dc sources that are used by the servo control circuitry (see paragraphs 2.5.1.1 through 2.5.1.6). 2.5.2.2When tuning coils L1 and L2 reach their upperlimit,themechanicaltravelindicatorwill obstruct the light-source path of U1 and it will turn off.Transistor Q7 will turn off.Darlington transistor Q9willturnoffandthe+15V-Asupplywillbe inhibited.Thisdisablesanyfurtherincrease commandsfromlocalorremoteswitchesorbythe automatic servo control circuit. 2.5.2.3When tuning coils L1 and L2 reach their lowerlimit,themechanicaltravelindicatorwill obstruct the light-source path of U2 and it will turn off.Transistor Q8 will turn off.Darlington transistor Q10willturnoffandthe+15V-Bsupplywillbe inhibited.Thisdisablesanyfurtherdecrease commandsfromlocalorremoteswitchesorbythe automatic servo control circuit. LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Page 2-4 01 March 2011 2.5.3FORWARD/REFLECTEDPOWER PROBE:VoltagetransformerT3andcurrent transformer T2 provide voltage and current arms of a forward/reflectedpowerbridgethatsamplestheRF output.Theanti-phasevoltagesacrossthe secondaries of T2 are summed with the voltage from T3 to provide voltages at the anode of diodes CR10 andCR11proportionaltotheforwardandreflected power.FORWARD/REFLECTEDswitch S3 selects the parameterfordisplayonfrontpanelmeterM1. CURRENT/RFPOWERswitchS7mustbesettoRF POWER and METER ON/OFF switch S8 must be set to ONtomeasureeitherFORWARDorREFLECTED power.RFPOWERpotentiometerR22providesa means of calibrating the front panel meter. 2.5.4 MATCHINGTRANSFORMER/ CURRENTPROBE:MatchingtransformerT4 transformsthesumofthecoillossresistanceand antenna series resistance on its output to a 50-ohm impedance on its input. The RF current through the lowseriesresonatednetantenna impedance passes through the primary of current transformer T5.The current transformed to the secondary winding flows through resistors R31/ R32, diodes CR19/CR20 and resistorsR29/R30,diodesCR18/CR21onalternate halfcycles.Thevoltageatthe cathode junction of diodesCR18/CR21,representativeoftheantenna current,isappliedtofrontpanelmeterM1via resistorR33,CURRENTpotentiometerR34and switches S7/S8.When 5/NORMAL switch S6 is set to NORMAL,theoutputofthebridgewillprovidean indication of the mean antenna current.The setting of momentary switch S6 to 5 will increase current meter reading by a factor of five, and permit more accurate measurement of low current readings. CURRENT/RF POWERswitchS7mustbesettoCURRENTand METERON/OFFswitchS8mustbesettoONto measurecurrent.CURRENTpotentiometerR34 provides a means of calibrating the front panel meter. VECTORSERIALINTERFACEPWB DETAILED CIRCUIT DESCRIPTION2.6The following descriptions provide a reader withanin-depthunderstandingofcomplexornon-obvious circuit functions. The descriptions are keyed totheblockdiagramSD-1andexpandonthe associated descriptions. Partial reference designations aregiveninthefollowingdescriptions.Unless otherwise specified, all reference designations in the followingparagraphsarepartofVectorserial interface PWB A2 (see electrical schematics SD-3 and SD-4). 2.6.1SERVOPROBE:TransformerT2 transforms the 50 RF current passing through the primary winding to the secondary windings. The RF current passing through T2s secondary is transformed tothesecondarywindingsofT1.Sincethe10-turn secondarywindingsofT1areidentical,theRF currentflowingineachwillbeinphase.Diode bridgesCR5/CR6/CR9/CR10and CR7/CR8/CR11/CR12 act as RF switches. They are alternatelyswitchedonandoff,onebytheRF currentspositivehalfcycleandtheotherbythe negative half cycle. The 50 Ohm RF In voltage signal (TB1-2) is applied to both diode bridges after being phase-shifted 90 by capacitor C1. 2.6.1.1If this voltage is exactly 90 out of phase with the current flowing in the 10-turn secondaries of transformer T1, the net dc potential, at the output of both diode bridges will be zero, since both will gate equal portions of the negative and positive half cycles. In this state the Inc_L and Dec_L signals applied to microcontroller U2 will be low. 2.6.1.2If the voltage from C1 is not exactly 90out ofphasewiththecurrentflowinginthe10-turn secondaries of transformer T1, the net dc output will be positive from one diode bridge and negative from the other. 2.6.1.3IftheoutputofdiodebridgeCR5/CR6/ CR9/CR10 goes positive, a high Inc_L signal and a low Dec_L signal will be applied to microcontroller U2. 2.6.1.4IftheoutputofdiodebridgeCR7/CR8/ CR11/CR120 goes positive, a high Dec_L signal and a low signal Inc_L will be applied to microcontroller U2. LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Page 2-5 01 March 2011 2.6.2POWERSUPPLIES:RegulatorU7and associatedcomponentsproducea+15Vdcsupply from the Vector transmitters dc supply. This supply is used to power the ATU control/monitor PWB (A1). The Vector dc supply is also applied to regulator U6 andassociatedcomponentstoproducea+5Vdc supply.The+5Vdcsupplyisusedtopowerthe microcontroller and control circuitry. 2.6.3CURRENT/VOLTAGESAMPLES: Current transformer T4 and resistors R10, R11, R16, and R17 provide a sample of the 50 ohm RF inputs current.DiodeCR13,voltagedividerR18andR20 and RF filter components R19, C14 and C12 provide a dc voltage (Current_Sample), proportional to the 50 ohmRFcurrentsample,tothemicrocontroller.A sample of the 50 ohm RF voltage (Voltage_Sample) is appliedtothemicrocontrollerthroughcomponents CR14,voltagedividerR21andR22,andRFfilter R23, C15 and C13. If the impedance at the ATUs RF inputis50ohms,theCurrent_Sampleand Voltage_Samplevoltageswillbeequal.Iftheinput impedance is less than 50 ohms, the Current_ Sample voltagewillbehigher.Iftheinputimpedanceis greater than 50 ohms the Voltage_Sample voltage will be higher. 2.6.4ANTENNACURRENTPROBE:TheRF current flowing into the ATUs tuning coils also flows through the primary winding of transformer T3. The currenttransformedtoT3ssecondarywinding flows through resistors R3/R4, diodes CR3/CR4 and resistorsthroughR1/R2,diodesCR1/CR2on alternatehalfcycles.Thevoltageatthecathode junction of diodes CR3/CR4 is representative of the antennacurrentAsampleoftheantennacurrent (Ant_Current_Sample)isappliedtothe microcontroller,viaANTCURSAMPLE potentiometer R6, through the RF filter comprised of R9, C2 and C3. 2.6.5MICROCONTROLLER:Microcontroller U2receivesanalog,digitalandserialinputsand providesdigitalandserialoutputs.The microcontrolleranditsassociatedcomponents controllocalandremoteoperation.The microcontroller also generates the ATUs alarms and status indications. 2.6.5.1AnalogInputs:MicrocontrollerU2 acceptsfiveanaloginputs:Voltage_Sample, Current_Sample,Ant_CurrentSample,Inc_Land Dec_L. All analog inputs have conditioning circuitry consisting of two diodes, to protect against excessive voltages on the microcontroller as well as a low pass R-C filter. 2.6.5.1.1TheInc_LandDec_Lsamplesare provided by the servo probe circuitry (see paragraph 2.6.1). These samples are used to determine whether moreorlessinductanceisneededtomatchthe capacitanceoftheantenna.U2willcontrolthe digitaloutputswhichactivatethemotorand associated LED indication (INCREASE L, NORMAL L or DECREASE L) for the loading coil accordingly. 2.6.5.1.2TheVoltage_SampleandCurrent_ Sample inputs are provided by the 50 ohm current probeandtheforwardreflectedprobevoltage transformer (see paragraph 2.6.3). These samples are usedtodeterminewhethertheinputresistanceis greaterorlessthantherequired50.U2will controlthedigitaloutputswhichactivatethe associated LED indication (INCREASE R, NORMAL R or DECREASE R) accordingly. 2.6.5.1.3The Ant_Current_Sample is provided by the antenna current probe (see paragraph 6.3.5). This sampleisappliedtotheassociatedtransmitter,via serialconnection,andisusedtocauseautomatic poweradjustmentstokeeptheantennacurrent constant. LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Page 2-6 01 March 2011 2.6.5.2DigitalInputs:8-bit shift register U4 and its associated components perform the conditioning required to process digital inputs. The digital inputs includethreepush-buttonswitchesforATU control/setup.Therearealsotwolimitswitches, whicharenotused,toprotecttheservofrom reaching its end limits. A clock input is applied to microcontrollerU2atpin10.WhenU2pin9is clearedandthenset,thecurrentdigitalinputsare loaded into U4. Data is shifted from U4-9 to U2-11. All switch inputs are momentary. 2.6.5.2.1Thefiveswitchesthataffectdatasentto themicrocontrollerare:INCREASEL(S4), DECREASE L (S3), INHIBIT L TUNING (S2), XMTR ON/OFF (S5) and LOCAL/REMOTE (S1). Only the LOCAL/REMOTEswitchwilloperateifthe ATU500 is in remote mode. 2.6.5.2.2TheINCREASELandDECREASEL switches control the inductive motor movement and activatetheinductivetuningmotorandinhibitthe Inc_LandDec_Lmicrocontrollerinputsfrom affecting the inductive tuning. 2.6.5.2.3INHIBITLTUNINGswitchdisablesthe ATU from auto tuning. Once the switch is pressed theautotunewillnotfunctionuntiltheswitchis pressed again. 2.6.5.2.4LOCAL/REMOTEswitchtogglesfrom localtoremotemode.Inremotemodeallother switches are inactive. 2.6.5.2.5XMTR ON/OFF enables the user to control a Vector series DGPS or NDB transmitter from the ATU. The microcontroller applies on/off commands to the transmitter via serial connection. 2.6.5.3DigitalOutputs:8-bitshiftregisterU5, microcontroller U2, and their associated components perform the conditioning required to produce digital outputs.Thedigitaloutputsconsistof12 status/alarmLEDsandthreemotorcontroloutputs andtwofancontroloutputs.Theseoutputsare shifted out of U2, using its SPI bus, into U5. U2 pin 26 is used to latch the current values to U5. 2.6.5.3.1Status/alarmLEDsincludeINHBL TUNING(DS5),LOCAL(DS4),INCRR(DS11), DECRR(DS9),NORMR(DS10),INCREASEL (DS8), DECREASEL (DS6), NORMALL (DS7), L MAX LIMIT (DS5, not used), L MIN LIMIT (DS9, not used), XMTR OFF (DS12) and CPU OK (DS3). 2.6.5.3.2TransistorsQ1throughQ3and associatedcomponentscontroltheinductivetune motors.Q2andQ3providethenecessaryopen collector Increase and Decrease outputs to the ATU control/monitor PWB to control the inductance. Q1 togglesbetween5Vand0VtosignaltheATU control/monitor PWB to Inhibit inductance tuning. 2.6.6SERIALCOMMUNICATIONS (RS485): Microcontroller U2, ICs U9 through U11 andtheirassociatedcomponentsformtheserial communicationscircuit.U9andU10areopto-isolatorsusedtoprovideisolationbetweenthe ATU500andtheassociatedtransmitter.U11 translatestheTTLoutputsfromU9andU10to balanced RS485. For /01 variations of the PWB, an isolated dc-dc converter (U8) supplies power to the transmittercircuit.For/02variationsofthePWB, thermistor RT1 isolates the power supply from the transmitter. LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Page 3-1 01 March 2011 SECTION 3 INSTALLATION AND PREPARATION FOR USE GENERAL 3.1This section contains the information required to prepare the site to receive the antenna tuning unit (ATU) and the information required to unpack, install and prepare the ATU for use. TEST EQUIPMENT 3.2Thetestequipmentrequiredforinitial installation and on-going maintenance is listed in table 1-2. SITE REQUIREMENTS 3.3TheautomaticATUshouldbeinstalledas close to the vertical (radiating) section of the antenna as is practical. It may be rear mounted on a grounded part of an antenna structure or a wall or base mounted. FigureMD-4showstheexternalandmounting dimensions to be used during the installation planning andconstructionstages.Itisrecommendedthata minimum of six inches clearance be provided at the baseoftheATUifcondensationreliefisrequired (through a user-installed micro-filter). The base of the ATU must be located at a higher elevation than any possible snow accumulation, to allow maintenance, to ensure proper ventilation (optional) and to prevent the possibility of water accumulation. 3.3.1PROXIMITYTOTRANSMITTER:The practice of locating the ATU and transmitter within a singlebuildingbeneaththeantennaisnot recommended.Itisextremelydifficulttoprovide adequateshieldingtopreventfeedbackbetweenthe high RF field of the antenna and the low signal level circuits of the transmitter. 3.3.2ANTENNASTRUCTURE:Theground planeshouldbearrangedsymmetricallyaroundthe antenna's vertical (radiating) section. Refer to figure 3-1foratypicalsitelayout.Adownleadinsulator similar to that depicted in figure 3-2 should be used to keepthedownleadundertension.Thisinsulatoris necessary to minimize movement of the downlead and torelieveanymechanicalstrainfromtheATU feedthroughinsulator.Thedownleadshouldbe positioned at least two feet away from the ATU or any othergroundedmetalstructuretominimizeantenna capacity change due to wind induced movement of the downlead. 3.3.3ANTENNAFEEDRFCABLE:The method by which the ATU output (J2) is connected to the antenna is very critical because of the very high voltage,currentandimpedancelevelsthatoccurat this interface. The antenna feed RF cable is connected to the feedthrough/insulator located at the top left of theATUcabinet.Thiscablemustbeofadequate diameter to avoid corona discharge, must not contain sharpbendsandshouldhavesufficientlengthto permit a drip loop at the feedthrough/ insulator. Refer to figure 3-2 for a typical connection to the downlead. 3.3.4EXTERNALCABLING:Externalpower and control connections are made through the side of the ATU cabinet via a liquid-tight connector.The RF input connection is made to N connector J1 at the side oftheATUcabinet.Wherepractical,itis recommended that the cabling between the transmitter andATUbeinstalledundergroundand,therefore, suitable for direct earth burial. 3.3.5RFTRANSMISSIONLINE:Asuitably rated, good quality, 50-ohm RF coaxial cable should be used to interconnect the ATU and the transmitter.The only penalty for long distances between the ATU andthetransmitteristhecostofthecableandthe powerlossinthecoaxialfeedercable.Thislossis typically 0.1 dB/100 m for a good quality, 1/2-inch diameter cable. 3.3.6DCPOWERCABLE:A5-conductor screenedcableshouldbeusedtointerconnectthe ATUandthetransmittertocarrythedcsupply voltageandtheremoteservooverridesignals.The wire gauge should be such that the loop resistance of a conductor pair does not exceed two ohms. LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Page 3-2 01 March 2011 Figure 3-1Typical Site Layout 3.3.7REMOTECONTROL/MONITOR WIRING:WhenoptionalVectorserialinterface PWB A2 is installed, the ATU can interface with a Nautel Vector series DGPS or NDB transmitter using RS-485 serial communication. Connections are made via a cable that passes through a liquid-tight connector in the side of the cabinet, to the ATU control/monitor PWB(9-pinDconnectorJ3orterminalsTB3-6 though TB3-10). The cable should be shielded (shield connected at the transmitter end only) and suitable for directearthburial,tobeinstalledunderground betweenthetransmitterandATU.TheRS-485 specification limits the cable length to a maximum of 4000 ft. (1220 m). The following pin-out and terminal assignment applies: +5VA2J 2-1 or A2TB3-2 GroundA2J 2-2 or A2TB3-3 TX/RXA2J 2-3 or A2TB3-4 TX/RXA2J 2-4 or A2TB3-5 DE/REA2J 2-5 or A2TB3-1 3.3.8GROUNDING:Agroundcable(6AWG minimum) must be connected between the centre of the antenna ground plane and the ground lug located onthebottom,left-handsideoftheATUcabinet.Thisgroundcableshouldbecontinuousanda very low resistance to ensure efficient operation. LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Page 3-3 01 March 2011 Figure 3-2Typical Downlead Insulator Installation UNPACKING 3.4The ATU is packed partially disassembled, in a wooden crate. A packing list, on the outside of the crate,providesadetailedlistingofcratecontents. Open the crate and remove the contents as follows: The ATU weighs 40 pounds. Sufficient manpower or mechanicalassistanceshouldbeavailablepriorto attempted removal. (a)Locatethecrateinaclearareathatwill permit extraction of the ATU without risk of damage to the unit or injury to personnel. (b)Stand the crate upright as marked on the side of the crate. (c)Removethecratepanelidentifiedasthefront from the crate by carefully prying it open using a small pry bar or other suitable tool. (d)Remove any small packages, as identified in the packing list, that are located between the outside of the ATU cabinet and the packing crate. (e)Carefully extract the ATU from the crate. LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Page 3-4 01 March 2011 Table 3-1Tuning Coil Inductance Values (uH) FREQUENCY (kHz) ANTENNA CAPACITY (pF) 190200250300350400450550 600 700 800 900 100011001200 1600 1700 1800125--3244225216551267 1001 670 563 414 317 250 203168141797063 200-3167202714081034792626419 352 259 198 156 12710588494439 2502808253416221126827633501335 282 207 158 125 1018470403531 300234021121351939690528417279 235 172 132 104 8470593329- 350200618101158804591452358239 201 148 113 8972605028-- 400175515841014704517396313209 176 129 9978635244--- 45015601408901626460352278186 156 115 8870564739--- 50014041267811563414317250168 141 103 7963514235--- 60011701056676469345264209140 117 866652423529--- 7001003905579402296226179120 101 7457453630---- 800877792507352259198156105 8865493932----- 900780704450313230176139937857443528----- 10007026334052822071581258470524031------ 11006385763692561881441147664473628------ 120058552833823517213210470594333------- 13005404873122171591229664544030------- 14005014522902011481138960503728------- 150046842227018813810683564734-------- 200035131720314110379634235--------- 30002342111359469534228---------- ANCILLARY PARTS 3 5An ancillary parts kit is provided with each ATU. These parts include external cabling termination connectorstoensureaproperinterfacewiththe connector mounted on the ATU. The ancillary parts areprovidedtoensuretheinitialinstallationisnot delayed because of a lost or missing part. They are not intendedtobelong-termmaintenancespares.An itemized listing of the ancillary parts kit is included in its packing list. USER SUPPLIED PARTS 3.6The user must supply all wiring and cabling that is external to the ATU. This includes dc power/ servo control from the transmitter site and the coaxial RF feed cable (terminated by a type N connector at the ATU end). LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Page 3-5 01 March 2011 USER DETERMINED INFORMATION: 3.7Determine the following information prior to final installation and initial calibration. 3.7.1CARRIERFREQUENCY:Determine/ record carrier frequency assigned to transmitter. 3.7.2ANTENNACAPACITANCE:Accurately determine/recordantennacapacitancefromantenna design records or by measurement. A Nautel technical paperentitledNDBAntennasmaybeusedto estimate antenna capacitance. 3.7.3ANTENNASERIESRESISTANCE: Accurately determine/record antenna series resistance (radiation plus ground resistance) from antenna design records or by measurement. PRE-INSTALLATION REQUIREMENTS 3.8Thefollowingproceduresmustbe observed prior to placing the automatic ATU in operation. 3.8.1TUNINGCOILPRE-INSTALLATION: The tuning coils and their associated ferrite cores must be installed and the coarse inductance selection must be made prior to placing the ATU in service. Proceed as follows: 3.8.1.1Tuning Coils: Two sets of tuning coils (high andlowinductance)areavailabletocoverthefull range of antenna capacities and operating frequencies. The high inductance coils cover the inductance range of87to3454uH,whilethelowinductancecoils cover the inductance range of 27 to 848 uH. Only one setofcoilsissuppliedwitheachATU.Thehigh inductance coils will be supplied unless engineering analysisofcustomerprovidedantennainformation dictates the use of low inductance coils or a customer specifically requests low inductance coils. (a)Entertable3-1withtheantennacapacity(see 3.7.2), the transmitter carrier frequency (see 3.7.1) and determine the required tuning coil inductance. (b)Verifytherequiredtuningcoilinductance determined in step (a) falls within the inductance rangeofthesuppliedtuningcoils,notinghigh inductance coils cover the inductance range of 87 to3454uHandlowinductancecoilscoverthe inductance range of 27 to 848 uH. 3.8.1.2SelectingTuningCoilTaps:Thetuning coilsmaybeconnectedin series or in parallel with severaltapconfigurations.Determinetheoptimum settings for a particular installation as follows: (a)Checkthepartnumbermarkedoneachtuning coiltodeterminewhetherthehighinductance coils(NautelPart#158-9028-01)orthelow inductancecoils(NautelPart#158-9028)have been supplied. (b)Entertable3-1withtheantennacapacity (recorded in paragraph 3.7.2) and the transmitter carrier frequency (recorded in paragraph 3.7.1) to determine the required tuning coil inductance. (c)Enterfigure3-3withtherequiredtuningcoil inductance to determine the required tuning coil tapconfigurationforhighinductanceorlow inductance coils [as determined in step (a)]. Wires connected to tuning coils L1 and L2 taps must bedressedinamannerthatwillpreventthemfrom coming in contact with other then the tap connecting points. Arcing that may result in damage to the coils and/or loss of tuning may result. (d)Choose jumper wires of suitable lengths from the ancillarypartstointerconnectthetuningcoils withtheconfigurationchosenfromfigure3-3. Notethattheoutputconnectionshouldbe connected to the tuning units high voltage feed-throughinsulatorJ2andtheinputconnection shouldconnectdirectlytotheRFOUTterminal (TB2-11)ontheATUcontrol/monitorPWB (A1). LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Page 3-6 01 March 2011 Table 3-2Tuning Coil Series Loss Resistance (Ohms) FREQUENCY (kHz)ANTENNA CAPACITY (pF)190200250300350400450550600700800900100011001200 1600 1700 180012533.531.825.521.218.215.9 14.1 11.6 10.6 9.18.07.16.45.85.34.03.73.5 20020.919.915.913.311.49.98.87.26.65.75.04.44.03.63.32.52.32.2 25016.815.912.710.69.18.07.15.85.34.54.03.53.22.92.72.01.91.8 30014.013.310.68.87.66.65.94.84.43.83.32.92.72.42.21.71.61.5 35012.011.49.17.66.55.75.14.13.83.22.82.52.32.11.91.41.31.3 40010.59.98.06.65.75.04.43.63.32.82.52.22.01.81.71.21.21.1 4509.38.87.15.95.14.43.93.22.92.52.22.01.81.61.51.11.01.0 5008.48.06.45.34.54.03.52.92.72.32.01.81.61.41.31.00.90.9 6007.06.65.34.43.83.32.92.42.21.91.71.51.31.21.10.80.80.7 7006.05.74.53.83.22.82.52.11.91.61.41.31.11.00.90.70.70.6 8005.25.04.03.32.82.52.21.81.71.41.21.11.00.90.80.60.60.6 9004.74.43.52.92.52.22.01.61.51.31.11.00.90.80.70.60.50.5 10004.24.03.22.72.32.01.81.41.31.11.00.90.80.70.70.50.50.4 11003.83.62.92.42.11.81.61.31.21.00.90.80.70.70.60.50.40.4 12003.53.32.72.21.91.71.51.21.10.90.80.70.70.60.60.40.40.4 13003.23.12.42.01.71.51.41.11.00.90.80.70.60.60.50.40.40.3 14003.02.82.31.91.61.41.31.00.90.80.70.60.60.50.50.40.30.3 15002.82.72.11.81.51.31.21.00.90.80.70.60.50.50.40.30.30.3 20002.12.01.61.31.11.00.90.70.70.60.50.40.40.40.30.20.20.2 30001.41.31.10.90.80.70.60.50.40.40.30.30.30.20.20.20.20.1 Table 3-3Selecting Matching Transformer Input/Output Taps MATCHINGTOTAL LOAD RESISTANCE (OHMS) TRANSFORMER TAPS3.724.55.66.68.0 10.0 12.515.019.023.028.035.041.050.060.5 INPUT (A Wire)456456456456455 OUTPUT (B Wire)101010999888777554 LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Page 3-7 01 March 2011 3.8.2ATUCONTROL/MONITORPWB PRE-INSTALLATION:Performthefollowingto the ATU control/monitor PWB (see figure MD-2) and itsmatchingtransformercircuitrypriortofinal installation: (a)Verifyallelectricalconnectionsaresecureand RF connections are firmly tightened. (b)Matchingtransformerconfiguration:Enter table 3-2 with the antenna capacity (recorded in paragraph3.7.2)andthetransmittercarrier frequency(recordedinparagraph3.7.1)and determine the tuning coil series loss resistance. (c)Determine the total load resistance by adding the tuning coil series loss resistance obtained in step (b)totheantennaseriesresistancerecordedin paragraph 3.7.3. (d)Entertable3-3withthetotalloadresistance obtained in step (c) and determine the matching transformer input and output taps to be used.If necessary, use the next higher tabulated resistance value. (e)Connect the RF input lead originating from A to theterminalofA1TB2identifiedastheInput (A Wire) connection. (f)Connect the RF output lead originating from B to the terminal of A1TB2 identified as the Output (B Wire) connection. 3.8.3SPARKGAPPRE-INSTALLATION: Thesparkgapshouldbeadjustedforoptimum lightning protection after calibration and testing of the RF tuned circuits has been completed. The spark gap islocatedonthetop,left-handsideofthecabinet, adjacenttotheinsulator/feedthrough,asdepictedin figure MD-1. Ensure the spark gap setting does not affect the RF circuits during calibration and testing by setting its opening to the maximum possible, prior to applyingRFpowertotheATUduringinitial installation,whenthetransmitterfrequencyis changedorwhentheantennacharacteristicsare altered. EXTERNAL CABLE CONNECTIONS 3.9Allelectricalinputconnections,from externalsources, are made through a cable entrance hole in the side of the cabinet. Refer to figure MD-4 for dimensional and locating information. Connect the external cabling to the automatic ATU as follows: (a)Connectdcpower/servo/communicationswiring to the ATU (see figure SD-2). If the Vector serial interfacePWB(A2)isinstalled,make connections to terminal block TB3 on the Vector serial interface PWB. If the Vector serial interface PWB (A2) is not installed, make connections to terminal block TB1 on the ATU control/monitor PWB (A1). (b)Install RF coaxial connector on RF input coaxial cable and mate RF input cable to connector J1 on the lower, right-hand side of the cabinet. (c)Connectthegroundingcablefromtheantenna ground plane to the ground lug on the lower, left-hand side of the cabinet. (d)ConnecttheantennaRFfeedcabletothe feedthrough/insulator(J2).Thefeedcablemust be arranged without sharp bends and must have a driploopadjacenttothefeedthrough/insulator connection. PLACING ATU IN SERVICE 3.10 PriortoplacingtheATUintoservice,a completeelectricalcalibrationandmechanical alignmentcheckmustbeperformed.Thesechecks must be done in conjunction with the antenna system to be used and the transmitter that will be the final RF output source. Observing the operating instructions of section 4, calibrate the automatic ATU and perform a functional test in accordance with the instructions in section 5. LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Page 3-8 01 March 2011 PARALLEL CONNECTION L2L1L2 L1 L2L1O/P 1 1 O/P 11O/P11 2 2 2222 3 3 3333 I/PI/PI/P 27 uH to 72 uH39 uH to 98 uH70 uH to 199 uH (Low Inductance Coil)(Low Inductance Coil)(Low Inductance Coil) 87 uH to 237 uH125 uH to 327 uH228 uH to 672 uH (High Inductance Coil)(High Inductance Coil)(High Inductance Coil) SERIES CONNECTION L2L1L2 L1 L2L1O/P 1 1 O/P 11O/P11 2 2 2222 3 3 3333 I/PI/PI/P 111 uH to 300 uH198 uH to 525 uH289 uH to 848 uH (Low Inductance Coil)(Low Inductance Coil)(Low Inductance Coil) 357 uH to 1015 uH649 uH to 1814 uH1003 uH to 3454 uH (High Inductance Coil)(High Inductance Coil)(High Inductance Coil) Figure 3-3Tuning Coil Tap Configurations LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Page 4-1 01 March 2011 WARNING SECTION 4 OPERATING INSTRUCTIONS GENERAL 4.1Thissectionprovidestheinformation requiredtoplacetheautomaticantennatuningunit (ATU)inoperation.TheATUwillnormallybe unattended during use. The following instructions are intendedforpersonsinvolvedintestingor maintenance of the equipment. Useextremecautioninthevicinityofthetuning coils.ExtremelyhighRFvoltages,thatmayjump manyinchesofairbreakdownpathandcancause severeRFburns,arepresentwhenanRFinputof any level is applied to the ATU. EMERGENCY SHUTDOWN 4.2Therearenospecialprocedurestobe observedifanemergencyshutdownisrequired. Remove RF input by having transmitter's RF output turned off or by disconnecting RF input coaxial cable from RF input connector J1. CONTROLS AND INDICATORS 4.3Allofthecontrolsandindicatorsforthe automatic antenna tuning unit are located on the ATU control/monitorPWB(A1)andtheoptionalVector serial interface PWB (A2). Figures MD-2 and MD-3 depictsthecontrolsandindicatorsforthesePWBs. Table4-1iskeyedtothereferencedesignation assignedtothecontrolsandindicatorsandexplain their functions. 4.3.1READINGREFLECTEDPOWER:The RFWATTSscale(upper)ofmeterA1M1followsa square law curve. The resulting non-linearity makes it difficulttoreadbelow1.0W.Forexample,an indicationthatishalfwaybetween0andthe1W division represents a power level of 0.25 W. PRESTART-UP CHECKS 4.4The following checks should be carried out prior to applying RF power or turning on the antenna tuningunit,tosafeguardagainstfailuresincurred duringtransitandinstallationandtoensuretheRF circuits are properly tuned to the transmitter frequency (a)Perform a visual inspection for obvious physical damage and missing parts. (b)Verifyallassembliesareproperlyinstalledand attaching hardware is securely fastened. (c)Verify pre-installation requirements of paragraph 3.8 are completed. (d)Verify external cable connection requirements of paragraph 3.9 are completed. (e)Verify the associated transmitter is turned on and dcvoltageisbeingappliedtoATUcontrol/ monitor PWB A1 (between 11 V and 16 V) and VectorserialinterfacePWBA2,ifinstalled (between 18 V and 24 V). (f)Verify two-way communications with transmitter site is available and operational. OPERATING PROCEDURES 4.5Hands-onoperationisnormallyused duringperformanceofmaintenanceprocedures. Operatetheantennatuningunitasdescribedin section 5 for specific maintenance procedures. SETTINGS FOR UNATTENDED OPERATION 4.6Whentheantennatuningunitistobe placedin unattended operation the controls must be set as follows: (a)Set POWERswitch A1S1 to ON.POWERlamp A1DS1 shall turn on. (b)SetAUTOswitchA1S2toON.AUTOlamp A1DS2 shall turn on. (c)Set METER ON/OFF switch A1S3 to OFF. LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Page 4-2 01 March 2011 WARNING PLACING ATU IN UNATTENDED OPERATION 4.7Place the antenna tuning unit in unattended operation as follows: (a)Verifyasuccessfulfunctionaltesthasbeen completed as described in section 5. (b)Performavisualinspectiontoensureall componentsareproperlyinstalledandalltest equipment and tools have been removed from the interior of the ATU cabinet. RFpowershouldbeturnedoffwhenworking around the tuning coils. Extremely high RF voltages are present when an RF input of any level is applied totheATU.Closeproximityorcontactwiththese high RF voltages can cause severe burns. (c)Verify the controls have been set as specified in paragraph 4.6. (d)Secure the cabinets front cover. LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Page 4-3 01 March 2011 Table 4-1: Antenna Tuning Unit Controls and Indicators PANEL MARKING/ REFFIGNOMENCLATUREFUNCTION DESNO.USED IN TEXT A1DS1MD-2POWERIndicates antenna tuning unit is switched on and dc input power is being applied when lamp is turned on. A1DS2MD-2AUTOIndicates the antenna tuning units servo control circuitry is enabled to automatically control the tuning of the loading coils. A1M1MD-2RF WATTS/RF AMPERESProvides meter indication of either the forward/reflected power (in watts, upper scale) or the mean value of the antenna current (in amperes, lower scale). A1R22MD-2RF POWERAdjusted to precisely calibrate meter A1M1 when an RFPOWER parameter (forward or reflected power) is being monitored. A1R34MD-2CURRENTAdjusted to precisely calibrate meter A1M1 when the RF current is being monitored. A1S1 MD-2POWERMain antenna tuning unit power switch. A1S2 MD-2AUTO ON/OFFEnables automatic servo control when set to ON. Inhibits automatic servo control when set to OFF. A1S3 MD-2FORWARD/REFLECTEDSelects RF output parameter, FORWARD or REFLECTED power, to be displayed on meter A1M1 when switch A1S7 is set to monitor RF POWER and METER ON/OFF switch is set to ON. A1S4 MD-2 INDUCTANCE - INCREASEManual fine-tuning control. Disconnects output of servo probe and causes tuning coil drive motor to operate in the direction that will increase inductance when activated (pressed and held). A1S5 MD-2INDUCTANCE - DECREASEManual fine-tuning control. Disconnects output of servo probe and causes tuning coil drive motor to operate in the direction that will decrease inductance when activated (pressed and held). A1S6 MD-25Increases RF AMPERES reading sensitivity on meter A1M1s lower scale by a factor of five when activated (pressed and held). Permits more accurate reading (2 A full-scale deflection) of low antenna currents. A1S7 MD-2CURRENT/RF POWERSelects parameter, CURRENT or RF POWER (forward or reflected), to be displayed on meter A1M1 when METERON/OFF switch is ON. A1S8 MD-2METER ON/OFFEnablesmeterA1M1todisplayselectedparameterwhensetto ON. LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Page 4-4 01 March 2011 Table 4-1: Antenna Tuning Unit Controls and Indicators (Continued) PANEL MARKING/ REFFIGNOMENCLATUREFUNCTION DESNO.USED IN TEXT A2DS1 MD-3L TUNING MAX LIMITNot Used A2DS2 MD-3L TUNING MIN LIMITNot Used A2DS3 MD-3CPU OKWhen flashing (green), indicates the Vector serial interface PWBs microcontroller is functional. A2DS4 MD-3LOCAL/REMOTEWhen turned on (amber), indicates the ATU is in local mode. A2DS5 MD-3L TUNING - INHIBITWhenturnedon(red),indicatesthattheATUsautomatic inductance tuning has been inhibited by pressing the LTUNING INHIBIT switch (A1S3) or via remote control. A2DS6 MD-3L TUNING - DECREASEWhen turned on (amber), indicates that the ATU is attempting to tune by decreasing the loading coil inductance. A2DS7 MD-3L TUNING - NORMALWhen turned on (green), indicates that the ATUs loading coils are properly tuned. A2DS8 MD-3L TUNING - INCREASEWhen turned on (amber), indicates that the ATU is attempting to tune by increasing the loading coil inductance. A2DS9 MD-3R TUNING - DECREASEWhen turned on (amber), indicates that the load resistance, as seen by the associated transmitter, is above 50 . Set the taps on the ATUsmatchingtransformerforthenexthighertotalload resistance to compensate for this (see paragraph 5.4.5). A2DS10MD-3R TUNING - NORMALWhenturnedon(green),indicatesthattheATUsmatching transformer is properly tuned. A2DS11MD-3R TUNING - INCREASEWhen turned on (amber), indicates that the load resistance, as seen by the associated transmitter, is below 50 . Set the taps on the ATUsmatchingtransformerforthenextlowertotalload resistance to compensate for this (see paragraph 5.4.5). A2DS12MD-3XMTR OFFWhen turned on (red), indicates the transmitters output power has been set to 0 W, via a serial communication link, using the XMTR ON/OFF switch (A1S8), if the transmitter is set to remote mode. A2DS13 MD-3+15VWhenturnedon(green),indicatesthe+15V-Aregulatedlow voltagepowersupply,whichsuppliestheinductancetuning control circuitry, is present. A2DS14MD-3+5VWhen turned on (green), indicates the +5 V regulated low voltage power supply is present. LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Page 4-5 01 March 2011 Table 4-1: Antenna Tuning Unit Controls and Indicators (Continued) PANEL MARKING/ REFFIGNOMENCLATUREFUNCTION DESNO.USED IN TEXT A2R51 MD-3ANT CUR SAMPLEFactory adjusted to provide an antenna current sample, monitored bytheassociatedtransmitterviaaseriallink,of4 Vwhenthe antenna current is 12 A. A2S1 MD-3LOCAL/REMOTEWhen pressed, .toggles between local and remote operation. In local mode, indicated by LED A1DS1 turning on, all remote controls are disabled. If a serial link was established between the ATU and a Nautel transmitter, the antenna current feedback loop is not intact. Inremotemode,indicatedLEDA1DS1turningoff,alllocal pushbuttons are disabled. A2S2 MD-3L TUNING - INHIBITWhen pressed (in local mode only), disables the ATUs automatic inductance tuning function. Associated LTUNINGINHIBIT LED will turn on. A2S3 MD-3L TUNING - DECREASEWhen pressed (in local mode only), causes a manual decrease in the ATUs loading coil inductance. If the ATU was tuned, the L TUNINGINCREASE LED will turn on, indicating the ATU is no longer tuned. The ATU will restore a tuned condition, if auto tuning is not inhibited. A2S4 MD-3L TUNING - DECREASEWhen pressed (in local mode only), causes a manual increase in the ATUs loading coil inductance. If the ATU was tuned, the L TUNING DECREASE LED will turn on, indicating the ATU is no longertuned.TheATUwillrestoreatunedcondition,ifauto tuning is not inhibited. A2S5 MD-3XMTR ON/OFFWhen pressed (in local mode only), with a serial communication link connected between the ATU and a Nautel transmitter, sets the transmittersremotepowertrimlevelto0V.AssociatedLED (A1DS2) will also turn on. If the transmitter is set to remote mode, the transmitters power will be reduced to 0 W. J1 MD-1RF InputProvides coaxial cable termination for RF input cable. NOTES: Ref Des items prefixed with A1 are part of ATU control/monitor PWB A1 Ref Des items prefixed with A2 are part of optional Vector serial interface PWB A2. LOW POWER AUTOMATIC ANTENNA TUNING UNIT ATU500 (NAT39D) Page 5-1 01 March 2011 SECTION 5 CALIBRATION AND TESTING GENERAL 5.1This section contains step-by-step calibration procedures for the antenna tuning unit (ATU) using precisiontestequipmentandafunctionaltest procedureusingintegralmeters.Itisrecommended thatpersonnelwhoarenotfamiliarwithdetailed circuit theory or do not realize what impact a specific adjustmentwillhaveonotherfunctions,follow instructions in the order presented. It is recommended that the instructions be followed sequentially during initial start-up. CALIBRATION TEST EQUIPMENT 5.2The test equipment required for calibration is listed in table 1-1. OPERATION OF EQUIPMENT 5.3OperationoftheATUisfullyautomatic except when the manual override switches are being activated.ExceptforthePOWERswitch,allofthe controls and indicators on the meter/control panel are provided as maintenance aids. Observe instructions in section4duringmaintenanceprocedures.Verify requirementsofparagraph4.4havebeencompleted prior to initial application of RF power. CALIBRATION PROCEDURES 5.4Acompletecalibrationwillnormallybe necessaryonlyduringinitialinstallationoraftera repair that affects the RF tuning or the tuning drive mechan