Assembly Instructions Chapter 3

3-kW UHF Transmitter Chapter 3, Installation and Setup Procedures
835-3, Rev. 0 3-2
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.