UBS Axcera 835-3 UHF television transmitter User Manual Chapter 3

UBS-Axcera UHF television transmitter Chapter 3

Chapter 3

3-kW UHF Transmitter Chapter 3, Installation and Setup Procedures835-3, Rev. 0 3-1Chapter 3Installation and Setup ProceduresThere are special considerations that need to be taken into account before the 835-3can be installed. For example, if the installation is completed during cool weather, aheat-related problem may not surface for many months, suddenly appearing during theheat of summer. This section provides planning information for the installation and setup of the transmitter.3.1 Site ConsiderationsThe 835-3 transmitter requires two main AC input lines, a 3-phase 208/240 VAC, 60 Hzinput of at least 100 amp rating that connects to the amplifier cabinet assembly and asingle-phase 208/240 VAC, 60 Hz input of at least 40 amp rating that connects to theexciter/driver assembly. Make sure that the proposed site has the necessary voltagerequirements.The 835-3 is designed and built to provide long life with a minimum of maintenance.The environment in which it is placed is important and certain precautions must betaken. The three greatest dangers to the transmitter are heat, dirt, and moisture. Heatis usually the greatest problem, followed by dirt, and then moisture. Over-temperaturecan cause heat-related problems such as thermal runaway and component failure. Eachamplifier tray in the transmitter contains a thermal interlock protection circuit that willshut down that tray until the temperature drops to an acceptable level.A suitable environment for the transmitter can enhance the overall performance andreliability of the transmitter and maximize revenues by minimizing down time. Aproperly designed facility will have an adequate supply of cool, clean air, free ofairborne particulates of any kind, and no excessive humidity. An ideal environment willrequire temperature in the range of 40° F to 70° F throughout the year, reasonably lowhumidity, and a dust-free room. It should be noted that this is rarely if ever attainablein the real world. However, the closer the environment is to this design, the greater theoperating capacity of the transmitter.The fans and blowers designed and built into the transmitter will remove the heat fromwithin the trays, but additional means are required for removing this heat from thebuilding. To achieve this, a few considerations should be taken into account. The firststep is to determine the amount of heat to be removed. There are generally threesources of heat that must be considered. The first and most obvious is the heat from thetransmitter itself. This can be determined by subtracting the average power to theantenna (2100 watts) from the AC input power (10,000 watts). This number in watts(15,900) is then multiplied by 3.41, which gives 54,200, the BTUs to be removed everyhour. 12,000 BTUs per hour equals one ton, so a 5-ton air conditioner will cool a 3-kWtransmitter that is vented into the room. If the air exhaust will be vented externally, a1-ton air conditioner will be needed to properly cool the transmitter. The second source of heat is other equipment in the same room. This number iscalculated in the same way as the equation for BTUs. The third source of heat is equallyobvious but not as simple to calculate. This is the heat coming through the walls, roof,and windows on a hot summer day. Unless the underside is exposed, the floor is usuallynot a problem. Determining this number is usually best left up to a qualified HVACtechnician. There are far too many variables to even estimate this number withoutdetailed drawings of the site showing all construction details. The sum of these three
3-kW UHF Transmitter Chapter 3, Installation and Setup Procedures835-3, Rev. 0 3-2sources is the total amount of heat that must be removed. There may be other sourcesof heat, such as personnel, and all should be taken into account. Now that the amount of heat that must be removed is known, the next step is todetermine how to accomplish this. The options are air conditioning, ventilation, or acombination of the two. Air conditioning is always the preferred method and is the onlyway to create anything close to an ideal environment.Ventilation will work if the ambient air temperature is below 100° F, or about 38° C,and the humidity is be kept at a reasonable level. In addition, the air stream must beadequately filtered to ensure that no airborne particulates of any kind will be carriedinto the transmitter. The combination of air conditioning for summer and ventilationduring the cooler months is acceptable when the proper cooling cannot be obtainedthrough the use of ventilation alone and using air conditioning throughout the year isnot feasible.Caution: The operation of air conditioning and ventilation simultaneously is notrecommended. This can cause condensation in transmitters. For tube typetransmitters, this can be especially serious if the condensation forms in thetube cavity and creates damaging arcs.The following precautions should be observed when using air conditioning systems:1. Air conditioners have an ARI nominal cooling capacity rating. In selecting an airconditioner, do not assume that this number can be equated to the requirementsof the site. Make certain that the contractor uses the actual conditions that are tobe maintained at the site in determining the size of the air conditioning unit.With the desired conditioned room temperature under 80° F, the unit must bederated, possibly by a substantial amount.2. Do not have the air conditioner blowing directly onto the transmitter.Condensation may occur on, or worse in, the transmitter under certainconditions.3. Do not isolate the front of the transmitter from the back with the thought of airconditioning only the front of the unit. Cooling air is drawn in at the front of alltransmitters and in the front and back of others. Any attempt to isolate the frontfrom the rear will adversely affect the cooling air flow.4. Interlocking the transmitter with the air conditioner is recommended to keep thetransmitter from operating without the necessary cooling. 5. The periodic cleaning of all filters is a must. When using ventilation alone, the following general statements apply:1. The blower and its filters should be on the inlet. This will pressurize the room andprevent dirt from entering the transmitter.2. The inlet and outlet vents should be on the same side of the building, preferablythe leeward side. As a result, the pressure differential created by wind will beminimized. Only the outlet vent should be released through the roof.
3-kW UHF Transmitter Chapter 3, Installation and Setup Procedures835-3, Rev. 0 3-33. The inlet and outlet vents should be screened with 1/8" hardware cloth(preferred) or galvanized hardware cloth (acceptable).4. Cooling air should enter the room as low as practical but in no case higher thanfour feet above the floor. The inlet must be located where dirt, leaves, snow, etc.,will not be carried in with the cooling air.5. The exhaust should be located as high as possible. Some ducting is usuallyrequired to insure the complete flushing of heated air with no stagnant areas.6. The filter area must be adequate to insure a maximum air velocity of 300 feet perminute through the filter. This is not a conservative number but a never-exceednumber. In a dusty or remote location, this number should be reduced to 150CFM.7. The inlet and outlet(s) must have automatic dampers that close any time theventilation blower is off.8. In those cases in which transmitters are regularly off for a portion of each day, atemperature-differential sensor that controls a small heater must be installed.This sensor will monitor inside and outside temperatures simultaneously. If theinside temperature falls to within 5° F of the outside temperature, the heater willcome on. This will prevent condensation when the ventilation blower comes onand should be used even in the summer.9. A controlled-air bypass system must be installed to prevent the temperature inthe room from falling below 40° F when the transmitter is operating.10. The blower should have two speeds, which are thermostatically controlled, andinterlocked with the transmitter.11. The blower on high speed must be capable of moving the required volume of airinto a half inch of water pressure at the required elevation. The free air deliverymethod must not be used.12. Regular maintenance of the filters, if used, can not be overemphasized.13. Tube transmitters should not rely on the internal blower to exhaust cooling air atelevations above 4000 feet. For external venting, the air vent on the cabinet topmust be increased to an 8" diameter for a 1 kW transmitter and to 15" for a 10-kW transmitter. An equivalent rectangular duct may be used but, in all cases, theoutlet must be increased in area by 50% through the outlet screen.14. It is recommended that a site plan be submitted to ADC for comments beforeinstallation commences.To calculate the blower requirements, filter size, and exhaust size if the total load isknown in watts, 2000 CFM into 1/2" of water will be required for each 5000 watts. If theload is known in BTUs, 2000 CFM into 1/2" of water will be required for each 17,000BTUs. The inlet filter must be a minimum of seven square feet, larger for dusty andremote locations, for each 5000 watts or 17,000 BTUs. The outlet for the exhaust mustbe at least four square feet at the exhaust screen for each 5000 watts or 17,000 BTUs. The information presented in this section is intended to serve only as a general guide
3-kW UHF Transmitter Chapter 3, Installation and Setup Procedures835-3, Rev. 0 3-4and may need to be modified for unusually severe conditions. A combination of airconditioning and ventilation should not be difficult to design. System interlocking andthermostat settings should be reviewed with ADC. As with any equipment installation, itis always good practice to consult the manufacturer when questions arise. ADC can becontacted at (724) 941-1500.3.2 Unpacking the Cabinets and TraysNote: Air conditioning and any related heat-exhaust ducts should be in placebefore continuing with the installation of the transmitter.Thoroughly inspect the cabinets and all other materials upon their arrival. ADC certifiesthat upon leaving our facility the equipment was undamaged and in proper workingorder. The shipping containers should be inspected for obvious damage that indicatesrough handling. Check for dents and scratches or broken switches, meters, orconnectors. Any claims against in-transit damage should be directed to the carrier.Inform ADC as to the extent of any damage as soon as possible.Remove the two cabinets, bandpass filter, trap filter, directional coupler, and installationmaterial that make up the 835-3 from the crates and boxes. Remove the straps thathold the cabinets to the shipping skid and slide the cabinets from the skid. Remove theplastic wrap and foam protection from around the cabinets. Do not remove any labelingor tags from any cables or connectors; these are identification markers that makeassembly of the transmitter much easier.Refer to the racking plan drawing (1595-7251) for the proper position of the cabinets. Position the exciter assembly with the 1-kW transmitter cabinet to the left of the 3-kWamplifier cabinet. The air intake to the transmitter is intended for room air only. Thecabinets should be positioned with consideration given for adequate air intake andexhaust; the opening of the rear doors; access to the trays, including sliding them outfor testing; the main AC hook-up; and the installation of the output transmission line.After positioning, the cabinets should be permanently mounted to the floor of the sitethrough the holes in the bottom of the cabinets. The cabinets also should be groundedusing copper strapping material.The trays are mounted in the cabinet using Chassis Trak cabinet slides. The tray slidesare on the top and bottom of the 600-watt amplifier trays and on the sides of the UHFexciter trays. Inspect the trays for any loose hardware or connectors, tightening whereneeded. Open the rear door; if a lock is present, the key to unlock the door is found in atan envelope taped to the door. Inspect the interior of the cabinet for packing materialand carefully remove any packing material that is found.3.3 Installing the Cabinets and TraysThe AC distribution panel from the 2-kW transmitter mounts into the left cabinet (seedrawing 1595-7251). Position the exciter for the 1-kW transmitter to the right of the ACdistribution panel even with the top. The two 600-watt amplifier trays for the 1-kWtransmitter mount at the bottom of the cabinet. The UHF exciter for the 3-kWtransmitter mounts at the top of the cabinet.Refer to the interconnect drawing (1176-8528) for point-to-point connections whiledoing the following procedure. Slide the six 600-watt amplifier trays into the amplifiercabinet on the right. Slowly slide each tray in and out to verify that they do not rubagainst each other and have no restriction to free movement. In the installationmaterial that has been provided with the transmitter, locate six equal length RG-55
3-kW UHF Transmitter Chapter 3, Installation and Setup Procedures835-3, Rev. 0 3-5coaxial cables with BNC connectors on both ends. Connect these cables from the (A9-A1) splitter to RF input jack J1 on each 600-watt amplifier tray. Also in the installationmaterial, should be six equal lengths of ½-inch superflex cable with N connectors oneach end. Connect the cables from the output of each amplifier tray at J2 to the 6-waycombiner. Connect the D connector jacks to J3 and J4 on the rear of each 600-wattamplifier tray.Caution: After installation, each 600-watt UHF amplifier tray will have ahardline coaxial cable connected to the rear panel. The tray will not slide outunless thisconnection is first removed. To pull out the tray for testing, use the extender coaxial cable included in theinstallation material kit to connect the tray to the output cable.Adjustments to the position of the trays may be necessary and are accomplished byloosening the cabinet slide mounting bolts that hold the front of the slide to themounting frame of the cabinet. Move the trays up or down, as needed, to correct for anyrubbing.3.4 Main AC Input ConnectionOnce the cabinets and the trays are in place, the main AC hookup is ready to be made. Caution: Before connecting the 230 VAC, make certain that all of the circuitbreakers associated with the transmitter are switched off. There are two ACinput circuits to the 3-kW transmitter: one 40 amp to the exciter and one 100amp to the amplifier cabinet.The 40-amp, 230-VAC input connections to the exciter cabinet are made to terminalblock TB1 in the AC distribution panel: connect line 1 to TB1-1A, line 2 to TB1-2A, andground to TB1-3A. Connect an AC power plug to an unused jack on the AC distributionpanel and connect the other end to J14 on the rear of the exciter tray. The AC to theUHF exciter tray can be switched off and on using the circuit breaker that is part of thepower entry module on the rear of the tray.Connect the 100-amp, 230-VAC input to terminal block A10-TB1. This terminal block ispart of the AC distribution assembly, 3-kW amplifier assembly (1245-1300), locatednear the center, right-hand side, rear portion of the cabinet. Connect line 1 to TB1-1,ground to TB1-2, and line 2 to TB1-3. Connect the AC power plugs to an unused jackson the AC distribution panel and connect the other end to J4 on the rear of each 600-watt amplifier tray. The AC to each tray can be switched off and on using the circuitbreakers on the AC distribution panel.The output of the amplifier assembly connects through (A5) a 1-5/8-inch to 3-1/8-inchadapter to (A9) a bandpass filter and (A10) an output trap filter assembly. The filteredoutput connects through (A11) the output coupler assembly (1020-1002) to thetransmission line that is connected to the antenna system.This completes the unpacking and installation of the 835-3 3-kW UHF transmitter. Referto the operation and setup procedures in the following section before applying power tothe transmitter.
3-kW UHF Transmitter Chapter 3, Installation and Setup Procedures835-3, Rev. 0 3-63.5 Operation and Setup ProceduresInitially, the transmitter should be turned on with the RF output at J2 of (A11) theoutput coupler assembly terminated into a dummy load of at least 3000 watts. If a loadis not available, check that the output of the coupler assembly is connected to theantenna.Connect the baseband, balanced audio input to XLR jack J5 or the composite audio,stereo, input to BNC jack J3 on the rear of the top UHF exciter tray for the 3-kWtransmitter. Connect the baseband video input to BNC jack J1 also on the rear of theUHF exciter assembly.Switch on the main AC and UHF exciter circuit breakers on the AC distribution panel inthe exciter cabinet. Switch on the main AC and all of the amplifier circuit breakers onthe AC distribution panel in the amplifier array cabinet. Also switch on the circuitbreaker on the rear of the UHF exciter tray for the 3-kW transmitter. Move theOperate/Standby switch on the front panel of the UHF exciter to Standby and move theAuto/Manual switch to Manual. Normal operation of the transmitter is with theAuto/Manual switch in Automatic. Automatic operation of the transmitter uses the videoinput to the UHF exciter as an Operate/Standby switch. In Auto, if the input video islost, the transmitter will automatically revert to Standby and, when the video signal isrestored, the transmitter will automatically return to Operate.Move the Operate/Standby switch on the UHF exciter tray to Operate. Note the powersupply reading, +28 VDC, on the front panel of each of the 600-watt amplifier trays. Note: If the transmitter does not switch to Operate when the Operate/Standbyswitch is moved to Operate, check that the external interlock plug, with ajumper from pins 23 to 24, is connected to jack J11 on the rear of the UHFexciter tray. Observe the % Output Power reading of the meter on the UHF exciter tray; it shouldread 100%. If needed, adjust the power adjust screwdriver adjust pot on the front panelof the UHF exciter. As the power level is being observed, check the meter reading in the% Reflected Power position. If the % Reflected Power is very high, above 40%, theremay be a problem with the output coaxial lines that needs to be checked and corrected.A center bullet missing from the 7/8-inch or 3 1/8-inch rigid coax lines or loose bolts onthe connections can cause this problem. Return the Operate/Standby switch to Standby.The gain and phase controls on the front panels of the individual 600-watt UHF amplifiertrays need to be adjusted to attain 100% output of the transmitter. The readings on theindividual trays may not all be the same. To set up the phasing and power adjustmentprocedure for the 600-watt amplifier trays, refer to Section 4, Detailed AlignmentProcedures, of this manual.If a dummy load is connected to the transmitter, switch the transmitter to Standby andswitch off the AC circuit breaker on the rear of the UHF exciter tray. Also switch off themain AC circuit breaker for the amplifier array cabinet. Remove the dummy load andmake all of the connections required to hook up the transmitter to the antenna. Switchon the UHF exciter and the amplifier array main AC circuit breaker. Move theOperate/Standby switch to Operate. Adjust the output power screwdriver pot to attain100% output.If the transmitter is already connected to the antenna, check that the output is 100%. Ifneeded, adjust the power screwdriver pot.
3-kW UHF Transmitter Chapter 3, Installation and Setup Procedures835-3, Rev. 0 3-7This completes the transmitter setup and operation procedure for the 835-3 3-kW UHFtransmitter. The transmitter can now be operated normally.

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