User's Manual

300-Watt Digital UHF Transmitter Chapter 3, Installation and Setup Procedures
DT830A, Rev. 1 3-2
Ventilation will work quite well 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
particulate 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 regarding 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, with attendant filters,
should be on the inlet, thereby
pressurizing the room and
preventing the ingress of dirt.
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 may be
released through the roof.
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