Section VII. RADIO INTERFERENCE SUPPRESSION
General Methods Used to Attain Proper
Essentially, suppression is attained by provide a
low resistance path to ground for stray currents. The
methods used include shielding the ignition and high-
frequency wires, grounding the frame with bonding
straps, and using capacitors and resistors.
The term interference as used herein applies to
electrical disturbances in the radio frequency range
which are generated by the special warfare printing plant
and which may interfere with the proper operation of
radio receivers or other electronic equipment, or may
enable the enemy to locate the equipment.
The term interference suppression as used
herein applies to the methods as used to eliminate or
effectively reduce radio interference generated by the
special warfare printing plant.
The items of equipment which make up the
editorial and photomechanical unit of the special warfare
printing plant have been chosen to meet military
requirements for radio interference suppression. All
electric motors are either of the brushless type or, as in
suppression features. The shelter construction is such
that radio interference from the fluorescent lighting or
other equipment is greatly reduced.
4-15. Interference Suppression Components.
The equipment installed within the shelter system
which could cause radio interference includes motors
installed in the platemaker, composing machine, and air
conditioner and the fluorescent lighting used for shelter
and light table illumination.
Motor Suppression. Motor suppression is
achieved through the use of capacitors and appropriate
shielding. Reference should be made to the applicable
technical publication for the type and location of
equipment radio suppression components.
Fluorescent Lighting Suppression. Fluorescent
lamps contain mercury vapor at low pressure. This
vapor is ionized by a flow of electrons in the tube. The
deionization that follows causes ultraviolet radiation
which excites the internal phosphor coating causing it to
radiate and give off light. The electron stream, or arc, in
the tube is a source of radio interference. The
interference may be radiated from the lamp or the power
leads, or transmitted by conduction through a common
power system. For systems that use starters, a
capacitor may be placed across the starter terminals.
Systems without starters usually have built-in capacitors
mounted in the ballast, or current limiting device. It is
impossible to suppress direct radiation from fluorescent
lamps since shielding defeats the purpose for which the
lamps are used.
4-16. Replacement of Suppression Components.
Refer to the applicable technical publication for
removal and installation of suppression components
used in the platemaker, composing machine, air
conditioning system and light table.
Testing of Radio Interference
Test capacitors for leaks and shorts on a capacitor
tester; replace defective capacitors. If test equipment is
not available and interference is indicated, isolate the
cause of interference by the trial and error method of
replacing each capacitor in turn until the cause is
located and eliminated.
Section VIII. MAINTENANCE OF CABINETS AND STORAGE COMPARTMENTS
4-18. File Cabinet Assembly.
The file cabinet assembly is a ten-drawer unit
installed at the left-hand shelter wall adjacent to the
compartments for storage of smaller items. Label
holders are attached to each to provide for content
fication labels. An upper and lower locking clip permits
insertion of a vertical locking bar to prevent movement
of the drawer during shipment and storage (See fig. 4-
7.) The cabinet, which is of welded metal construction is
used for storage of artist historic files and supplies.