Installation Instructions Chapter 4

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500-Watt VHF Low Band Transmitter Chapter 4, Installation and Setup Procedures

325A, Rev. 0 4-1

Chapter 4

Installation and Setup Procedures

There are special considerations that

need to be taken into account before the

325A 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.

4.1 Site Considerations

The transmitter requires an AC input line

of 220 VAC with a rating of 40 amps for

the exciter/amplifier cabinet. Make sure

that the proposed site for the transmitter

has the necessary voltage requirements.

The 325A 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 issues need to be resolved. The first

step is to determine the amount of heat

to be removed from the transmitter

room. 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 (350 watts) from the AC input

power (3500 watts). This number in

watts (3150) is then multiplied by 3.41,

which gives 10,741, the BTUs to be

removed every hour. 12,000 BTUs per

hour equals one ton, so a 1-ton air

conditioner will cool a 500-watt

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 reviewing the detailed

drawings of the site that show all of the

construction details. The sum of these

three sources is the bulk of the 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

Summary of content (7 pages)

PAGE 1
500-Watt VHF Low Band Transmitter Chapter 4, Installation and Setup Procedures Chapter 4 Installation and Setup Procedures There are special considerations that need to be taken into account before the 325A 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.
PAGE 2
500-Watt VHF Low Band Transmitter Chapter 4, Installation and Setup Procedures 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. transmitter. Condensation may occur on, or worse in, the transmitter under certain conditions.
PAGE 3
500-Watt VHF Low Band Transmitter Chapter 4, Installation and Setup Procedures 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 large enough to insure a maximum air velocity of 300 feet per minute through the filter. This is not a conservative number but a neverexceed number.
PAGE 4
500-Watt VHF Low Band Transmitter Chapter 4, Installation and Setup Procedures As with any equipment installation, it is always good practice to consult the manufacturer when questions arise. Axcera can be contacted at (724) 8738100. Figure 4-1. 1 kW Minimum Ventilation Configuration 4.2 Unpacking the Cabinets and Trays Remove the cabinet and the trays from the crates and boxes. Remove the straps that hold the cabinet to the shipping skid and slide the cabinet from the skid.
PAGE 5
00-Watt VHF Low Band Transmitter Chapter 4, Installation and Setup Procedures Figure 4-2. Chassis Trak Cabinet Slides Open the rear door. Inspect the interior of the cabinet for packing materials and carefully remove any packing materials that are found. Slowly slide each tray in and out to verify that they do not rub against each other and have no restrictions to free movement. Once the cabinet is in place, and the trays are checked for damage, the main AC hookup can be made.
PAGE 6
500-Watt VHF Low Band Transmitter Chapter 4, Installation and Setup Procedures 4.4 Setup and Operation the 4.5-MHz composite input must be connected to J2 and the baseband select must be removed from J7-6 and J7-7 on the rear of the VHF exciter tray. To use the baseband video and audio inputs, the baseband video input must be connected to J2, the baseband audio must be connected to the proper jack, and the baseband select must be connected from J7-6 and J7-7 on the rear of the VHF exciter tray.
PAGE 7
500-Watt VHF Low Band Transmitter Chapter 4, Installation and Setup Procedures If necessary, readjust the screwdriver adjust power pot on the front panel of the VHF exciter for 100%. As the power level is being checked, observe the meter reading in the % Reflected Power position. If the % Reflected Power is very high, above 10%, a problem exists with the output coaxial lines and they will need to be checked.