Nautel NX5 AM, Preinstallation Manual

Page: 40 / 89

NX5 PRE-INSTALLATION MANUAL COOLING REQUIREMENTS
VERSION 0.1 2015-08-01 PAGE 1.4.3
Cooling
Do not allow the transmitter room ambient air temperature to exceed 50°C (122°F) at sea level. Cooler
temperatures are recommended in order to improve the reliability of the transmitter. At higher altitudes,
derate the maximum inlet air temperature as follows:
 De-rate the ambient temperature 3ºC (5.4°F) per 500 m – or 2ºC (3.6°F) per 1,000
feet – above sea level.
Example:
At 1600 m (1 mile) above sea level, maximum ambient temperature should not
exceed 40.4ºC (104.7°F).
Note:
Ensure hot air from the transmitter is not drawn back into the transmitter’s cool air intake.
Cooling Plant Requirements
The NX5’s efficiency is typically 86%. Calculate the power dissipated by the transmitter using the
following equation:
Where n is the transmitter’s efficiency and P
out
is the transmitter’s average output power. For
continuous tone modulation, calculate the average output power of the transmitter using the following
equation:
Where m is the modulation depth and P
c
is the transmitter’s output carrier power.
Table 1.4.1 on page 1.4.4 shows the cooling requirements for the transmitter when operating with
various continuous tone modulation levels. To determine the number of British thermal units (Btu) being
generated per hour as waste heat, multiply the waste heat (in watts) by 3.413. To determine the air
conditioning (in tonnes), multiply the waste heat (in watts) by 0.000285.