CHAPTER 10
ELECTROSTATIC DISCHARGE PROGRAM
The electrical noise generated in a radio or radar
receiver is often confused with electrical noise
generated external to the receiver and coupled into the
receiver. The internally generated noise is the result
of circuit deficiencies in the receiver itself, and can be
eliminated by replacing the defective component or
replacing the entire receiver. Electrical noise
produced external to the receiver enters the receiver
by various means. The noise causes interference in
the receiver, as well as poor reception.
In early naval aircraft, electrical noise inter-
ference was not a major problem because there were
fewer external sources of electrical noise. Receiver
sensitivities were low, and the aircraft control
components were manually operated. In today’s
aircraft, however, there are considerably more
sources of externally generated electrical noise. The
aircraft now contains numerous receivers with higher
sensitivities, and the aircraft controls are operated by
various electrical and/or mechanical devices. These
devices include control surface drive motors, fuel and
hydraulic boost pumps, ac inverters, and cabin
pressurization systems. In addition, pulsed electronic
transmitters, such as TACAN, radar, and IFF, can be
sources of electrical noise interference. Listening to
electrical noise interference in the output of a radio
receiver can cause nervous fatigue in aircrew
personnel. Electrical noise may also reduce the
performance (sensitivity) of the receiver. For these
reasons, electrical noise should be kept at the lowest
possible level.
The overall objective of this chapter is to assist
you in recognizing various types of electrical/
electronic noise, their effects on radio and radar
receivers, and what the electrostatic discharge
program means to you as the work center supervisor.
This chapter also provides you with information for
keeping electrical noise interference as low as
possible in electronic equipment aboard naval
aircraft.
TYPES AND EFFECTS OF RECEIVER
NOISE INTERFERENCE
Learning Objective: Recognize the types and
effects of radio noise, including natural and
man-made interference.
The types of electrical noise interference that
enter aircraft receivers are broadly categorized as
natural interference and man-made interference.
NATURAL INTERFERENCE
Radio interference caused by natural electrical
noise is separated into three types: atmospheric
static, precipitation static, and cosmic noise. Each
type is discussed below.
Atmospheric Static
Atmospheric static is a result of the electrical
breakdown between masses (clouds) of oppositely
charged particles in the atmosphere. An extremely
large electrical breakdown between two clouds or
between the clouds and ground is called “lightning.”
Atmospheric static is completely random in nature,
both as to rate of recurrence and as to intensity of
individual discharges. Atmospheric static produces
irregular popping and crackling in audio outputs and
“grass” on visual output devices. Its effects range
from minor annoyance to complete loss of receiver
usefulness. Atmospheric interference is seldom of a
crippling intensity at frequencies from 2 MHz to 30
MHz, but it can be annoying. Above 30 MHz, the
noise intensity decreases to a very low level. At
frequencies below 2 MHz, natural static is the
principal limiting factor on usable receiver sensitivity.
The intensity of atmospheric static varies with
location, season, weather, time of day, and the
frequency to which the receiver is tuned. It is most
intense at the lower latitudes, during the summer
season, during weather squalls, and at the lower radio
frequencies. Many schemes have been devised to
minimize the effects of atmospheric static. However,
the best technique is to avoid those frequencies
associated with intense static, if possible.
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