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

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Document ID	108439
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Document Description	Chapter 3
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Document Type	User Manual
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Date Submitted	2000-07-10 00:00:00
Date Available	2000-08-16 00:00:00
Creation Date	2000-07-10 11:39:06
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Document Lastmod	2000-07-10 11:39:08
Document Title	Chapter 3

3-kW UHF Transmitter
Chapter 3, Installation and Setup Procedures
Chapter 3
Installation and Setup Procedures
There are special considerations that need to be taken into account before the 835-3
can be installed. For example, if the installation is completed during cool weather, a
heat-related problem may not surface for many months, suddenly appearing during the
heat of summer. This section provides planning information for the installation and set
up of the transmitter.
3.1 Site Considerations
The 835-3 transmitter requires two main AC input lines, a 3-phase 208/240 VAC, 60 Hz
input of at least 100 amp rating that connects to the amplifier cabinet assembly and a
single-phase 208/240 VAC, 60 Hz input of at least 40 amp rating that connects to the
exciter/driver assembly. Make sure that the proposed site has the necessary voltage
requirements.
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 be
taken. The three greatest dangers to the transmitter are heat, dirt, and moisture. Heat
is usually the greatest problem, followed by dirt, and then moisture. Over-temperature
can cause heat-related problems such as thermal runaway and component failure. Each
amplifier tray in the transmitter contains a thermal interlock protection circuit that will
shut down that tray until the temperature drops to an acceptable level.
A suitable environment for the transmitter can enhance the overall performance and
reliability of the transmitter and maximize revenues by minimizing down time. A
properly designed facility will have an adequate supply of cool, clean air, free of
airborne particulates of any kind, and no excessive humidity. An ideal environment will
require temperature in the range of 40° F to 70° F throughout the year, reasonably low
humidity, and a dust-free room. It should be noted that this is rarely if ever attainable
in the real world. However, the closer the environment is to this design, the greater the
operating capacity of the transmitter.
The fans and blowers designed and built into the transmitter will remove the heat from
within the trays, but additional means are required for removing this heat from the
building. To achieve this, a few considerations should be taken into account. The first
step is to determine the amount of heat to be removed. There are generally three
sources of heat that must be considered. The first and most obvious is the heat from the
transmitter itself. This can be determined by subtracting the average power to the
antenna (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 every
hour. 12,000 BTUs per hour equals one ton, so a 5-ton air conditioner will cool a 3-kW
transmitter that is vented into the room. If the air exhaust will be vented externally, a
1-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 is
calculated in the same way as the equation for BTUs. The third source of heat is equally
obvious 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 usually
not a problem. Determining this number is usually best left up to a qualified HVAC
technician. There are far too many variables to even estimate this number without
detailed drawings of the site showing all construction details. The sum of these three
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3-kW UHF Transmitter
Chapter 3, Installation and Setup Procedures
sources is the total amount of heat that must be removed. There may be other sources
of 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 to
determine how to accomplish this. The options are air conditioning, ventilation, or a
combination of the two. Air conditioning is always the preferred method and is the only
way 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 be
adequately filtered to ensure that no airborne particulates of any kind will be carried
into the transmitter. The combination of air conditioning for summer and ventilation
during the cooler months is acceptable when the proper cooling cannot be obtained
through the use of ventilation alone and using air conditioning throughout the year is
not feasible.
Caution: The operation of air conditioning and ventilation simultaneously is not
recommended. This can cause condensation in transmitters. For tube type
transmitters, this can be especially serious if the condensation forms in the
tube 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 air
conditioner, do not assume that this number can be equated to the requirements
of the site. Make certain that the contractor uses the actual conditions that are to
be 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 be
derated, 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 certain
conditions.
3.
Do not isolate the front of the transmitter from the back with the thought of air
conditioning only the front of the unit. Cooling air is drawn in at the front of all
transmitters and in the front and back of others. Any attempt to isolate the front
from the rear will adversely affect the cooling air flow.
4.
Interlocking the transmitter with the air conditioner is recommended to keep the
transmitter 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 and
prevent dirt from entering the transmitter.
2.
The inlet and outlet vents should be on the same side of the building, preferably
the leeward side. As a result, the pressure differential created by wind will be
minimized. Only the outlet vent should be released through the roof.
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3-kW UHF Transmitter
Chapter 3, Installation and Setup Procedures
3.
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 than
four 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 usually
required 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 per
minute through the filter. This is not a conservative number but a never-exceed
number. In a dusty or remote location, this number should be reduced to 150
CFM.
7.
The inlet and outlet(s) must have automatic dampers that close any time the
ventilation blower is off.
8.
In those cases in which transmitters are regularly off for a portion of each day, a
temperature-differential sensor that controls a small heater must be installed.
This sensor will monitor inside and outside temperatures simultaneously. If the
inside temperature falls to within 5° F of the outside temperature, the heater will
come on. This will prevent condensation when the ventilation blower comes on
and should be used even in the summer.
9.
A controlled-air bypass system must be installed to prevent the temperature in
the room from falling below 40° F when the transmitter is operating.
10.
The blower should have two speeds, which are thermostatically controlled, and
interlocked with the transmitter.
11.
The blower on high speed must be capable of moving the required volume of air
into a half inch of water pressure at the required elevation. The free air delivery
method 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 at
elevations above 4000 feet. For external venting, the air vent on the cabinet top
must be increased to an 8" diameter for a 1 kW transmitter and to 15" for a 10kW transmitter. An equivalent rectangular duct may be used but, in all cases, the
outlet 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 before
installation commences.
To calculate the blower requirements, filter size, and exhaust size if the total load is
known in watts, 2000 CFM into 1/2" of water will be required for each 5000 watts. If the
load is known in BTUs, 2000 CFM into 1/2" of water will be required for each 17,000
BTUs. The inlet filter must be a minimum of seven square feet, larger for dusty and
remote locations, for each 5000 watts or 17,000 BTUs. The outlet for the exhaust must
be 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
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3-kW UHF Transmitter
Chapter 3, Installation and Setup Procedures
and may need to be modified for unusually severe conditions. A combination of air
conditioning and ventilation should not be difficult to design. System interlocking and
thermostat settings should be reviewed with ADC. As with any equipment installation, it
is always good practice to consult the manufacturer when questions arise. ADC can be
contacted at (724) 941-1500.
3.2 Unpacking the Cabinets and Trays
Note: Air conditioning and any related heat-exhaust ducts should be in place
before continuing with the installation of the transmitter.
Thoroughly inspect the cabinets and all other materials upon their arrival. ADC certifies
that upon leaving our facility the equipment was undamaged and in proper working
order. The shipping containers should be inspected for obvious damage that indicates
rough handling. Check for dents and scratches or broken switches, meters, or
connectors. 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 installation
material that make up the 835-3 from the crates and boxes. Remove the straps that
hold the cabinets to the shipping skid and slide the cabinets from the skid. Remove the
plastic wrap and foam protection from around the cabinets. Do not remove any labeling
or tags from any cables or connectors; these are identification markers that make
assembly 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-kW
amplifier cabinet. The air intake to the transmitter is intended for room air only. The
cabinets should be positioned with consideration given for adequate air intake and
exhaust; the opening of the rear doors; access to the trays, including sliding them out
for 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 site
through the holes in the bottom of the cabinets. The cabinets also should be grounded
using copper strapping material.
The trays are mounted in the cabinet using Chassis Trak cabinet slides. The tray slides
are on the top and bottom of the 600-watt amplifier trays and on the sides of the UHF
exciter trays. Inspect the trays for any loose hardware or connectors, tightening where
needed. Open the rear door; if a lock is present, the key to unlock the door is found in a
tan envelope taped to the door. Inspect the interior of the cabinet for packing material
and carefully remove any packing material that is found.
3.3 Installing the Cabinets and Trays
The AC distribution panel from the 2-kW transmitter mounts into the left cabinet (see
drawing 1595-7251). Position the exciter for the 1-kW transmitter to the right of the AC
distribution panel even with the top. The two 600-watt amplifier trays for the 1-kW
transmitter mount at the bottom of the cabinet. The UHF exciter for the 3-kW
transmitter mounts at the top of the cabinet.
Refer to the interconnect drawing (1176-8528) for point-to-point connections while
doing the following procedure. Slide the six 600-watt amplifier trays into the amplifier
cabinet on the right. Slowly slide each tray in and out to verify that they do not rub
against each other and have no restriction to free movement. In the installation
material that has been provided with the transmitter, locate six equal length RG-55
835-3, Rev. 0
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3-kW UHF Transmitter
Chapter 3, Installation and Setup Procedures
coaxial cables with BNC connectors on both ends. Connect these cables from the (A9A1) splitter to RF input jack J1 on each 600-watt amplifier tray. Also in the installation
material, should be six equal lengths of ½-inch superflex cable with N connectors on
each end. Connect the cables from the output of each amplifier tray at J2 to the 6-way
combiner. Connect the D connector jacks to J3 and J4 on the rear of each 600-watt
amplifier tray.
Caution: After installation, each 600-watt UHF amplifier tray will have a
hardline coaxial cable connected to the rear panel. The tray will not slide out
unless this
connection is first removed.
To pull out the tray for testing, use the extender coaxial cable included in the
installation material kit to connect the tray to the output cable.
Adjustments to the position of the trays may be necessary and are accomplished by
loosening the cabinet slide mounting bolts that hold the front of the slide to the
mounting frame of the cabinet. Move the trays up or down, as needed, to correct for any
rubbing.
3.4 Main AC Input Connection
Once 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 circuit
breakers associated with the transmitter are switched off. There are two AC
input circuits to the 3-kW transmitter: one 40 amp to the exciter and one 100
amp to the amplifier cabinet.
The 40-amp, 230-VAC input connections to the exciter cabinet are made to terminal
block TB1 in the AC distribution panel: connect line 1 to TB1-1A, line 2 to TB1-2A, and
ground to TB1-3A. Connect an AC power plug to an unused jack on the AC distribution
panel and connect the other end to J14 on the rear of the exciter tray. The AC to the
UHF exciter tray can be switched off and on using the circuit breaker that is part of the
power entry module on the rear of the tray.
Connect the 100-amp, 230-VAC input to terminal block A10-TB1. This terminal block is
part of the AC distribution assembly, 3-kW amplifier assembly (1245-1300), located
near 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 jacks
on the AC distribution panel and connect the other end to J4 on the rear of each 600watt amplifier tray. The AC to each tray can be switched off and on using the circuit
breakers on the AC distribution panel.
The output of the amplifier assembly connects through (A5) a 1-5/8-inch to 3-1/8-inch
adapter to (A9) a bandpass filter and (A10) an output trap filter assembly. The filtered
output connects through (A11) the output coupler assembly (1020-1002) to the
transmission line that is connected to the antenna system.
This completes the unpacking and installation of the 835-3 3-kW UHF transmitter. Refer
to the operation and setup procedures in the following section before applying power to
the transmitter.
835-3, Rev. 0
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3-kW UHF Transmitter
Chapter 3, Installation and Setup Procedures
3.5 Operation and Setup Procedures
Initially, the transmitter should be turned on with the RF output at J2 of (A11) the
output coupler assembly terminated into a dummy load of at least 3000 watts. If a load
is not available, check that the output of the coupler assembly is connected to the
antenna.
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-kW
transmitter. Connect the baseband video input to BNC jack J1 also on the rear of the
UHF exciter assembly.
Switch on the main AC and UHF exciter circuit breakers on the AC distribution panel in
the exciter cabinet. Switch on the main AC and all of the amplifier circuit breakers on
the AC distribution panel in the amplifier array cabinet. Also switch on the circuit
breaker on the rear of the UHF exciter tray for the 3-kW transmitter. Move the
Operate/Standby switch on the front panel of the UHF exciter to Standby and move the
Auto/Manual switch to Manual. Normal operation of the transmitter is with the
Auto/Manual switch in Automatic. Automatic operation of the transmitter uses the video
input to the UHF exciter as an Operate/Standby switch. In Auto, if the input video is
lost, the transmitter will automatically revert to Standby and, when the video signal is
restored, the transmitter will automatically return to Operate.
Move the Operate/Standby switch on the UHF exciter tray to Operate. Note the power
supply 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/Standby
switch is moved to Operate, check that the external interlock plug, with a
jumper from pins 23 to 24, is connected to jack J11 on the rear of the UHF
exciter tray.
Observe the % Output Power reading of the meter on the UHF exciter tray; it should
read 100%. If needed, adjust the power adjust screwdriver adjust pot on the front panel
of 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%, there
may 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 on
the 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 amplifier
trays need to be adjusted to attain 100% output of the transmitter. The readings on the
individual trays may not all be the same. To set up the phasing and power adjustment
procedure for the 600-watt amplifier trays, refer to Section 4, Detailed Alignment
Procedures, of this manual.
If a dummy load is connected to the transmitter, switch the transmitter to Standby and
switch off the AC circuit breaker on the rear of the UHF exciter tray. Also switch off the
main AC circuit breaker for the amplifier array cabinet. Remove the dummy load and
make all of the connections required to hook up the transmitter to the antenna. Switch
on the UHF exciter and the amplifier array main AC circuit breaker. Move the
Operate/Standby switch to Operate. Adjust the output power screwdriver pot to attain
100% output.
If the transmitter is already connected to the antenna, check that the output is 100%. If
needed, adjust the power screwdriver pot.
835-3, Rev. 0
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3-kW UHF Transmitter
Chapter 3, Installation and Setup Procedures
This completes the transmitter setup and operation procedure for the 835-3 3-kW UHF
transmitter. The transmitter can now be operated normally.
835-3, Rev. 0
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