TM 5-4320-218-15
(pars.
(pars.
136 through 138).
136 through 138).
(pars. 136 through 138).
(pars.
136 through 138).
Section V. RADIO SUPPRESSION
45. Definition of Radio Suppression
47. Sources of Interference
Radio suppression is the effective elimination
The spark plugs, ignition wires from mag-
of electrical disturbances within the equipment
neto to spark plugs, and poor electrical connec-
which interfere with radio reception, and
tions are common sources of electrical interfer-
disclose the location of the pump and the other
ence.
components of the installation to sensitive elec-
48. Methods Used to Suppress
trical detectors.
Interference
46. Suppression Component Replacement
a. General. The following three methods
a. General When replacing suppression ma-
are used to suppress radio interference caused
terial it is necessary to replace defective com-
by the unit:
ponents with identical parts. Any shielding or
(1) Capacitors.
any engine accessory which is shielded for radio
(2) Bonding.
suppression must be grounded and secured
(3) Shielding.
with screws and lockwashers. Grounding
b. Capacitors. The capacitors are units of
contacts must be clean and tight for satisfac-
metal foils separated by paper insulation and
tory interference suppression.
protected by a metal case filled with an impreg-
b. Engine suppression material.
nation compound to keep moisture out. The
(1) Spark plugs. Each spark plug is self-
capacitor is attached to the circuit as close as
shielded with one 10,000-ohm resis-
possible to the point at which the spark occurs.
tor-suppressor inserted at the plug
A capacitor allows the interfering voltage to
end of each high-tension lead, Al-
pass freely to ground, and, at the same time,
ways replace with the same type
prevents loss of useful current.
when changing plugs. Each cable as-
c. Bonding. Bonding is accomplished by in-
sembly is covered with a thin copper
ternal-external-toothed lockwashers and by
braid which must be grounded at
bond straps. Bonding is necessary to provide
both ends of the lead for proper sup-
an easy path for grounding static charges. The
pression. See that the plugs and leads
better the connection between metal parts, the
are clean and tight.
greater is the effect in preventing interfering
( 2 )Magneto. The magneto is bonded to
waves from being broadcasted to affect radio
the engine front cover with lockwash-
reception.
ers and cap screws. A ground wire
d. Shielding Shielding is accomplished by
from the magneto frame to the crank-
covering with metal shields or boxing all
case provides a good ground.
