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 MIL-HDBK-419A
shields and an insulated conductor from strapped terminals to the insulated copper ground frame distribution
cable behind the vertical and horizontal terminal blocks. The insulated conductor was brazed to the insulated
signal ground plane near the distribution frames served. If a jumper wire was used from the distribution cable
to the signal ground plane, a minimum of #10 AWG stranded conductor would generally suffice (see
Figures 1-67, 1-68, and 2-18).
Other Protection Grounds. The signal ground is an earth ground which should be controlled. It is
f.
recognized that a ground system contained within a controlled space (CS) is not always possible. In this case
other alternatives were considered. Notwithstanding the limitations associated with water pipes, they were
however used as a single ground point. Another somewhat acceptable ground point was the case of the old
cryptographic equipment (see Figures 2-19 and 2-20) which did not have any means to attach a ground feeder
conductor to the equipment case. As noted in Figure 2-19A, the green wire ground connection in the power
panel serving the cryptographic units was sometimes used.
2.4.5 Signal Filter Ground. To minimize the degradation of filter insertion-loss characteristics due to a
nonzero impedance between the filter case and earth ground, filters were mounted directly on a ground
reference plane. This ground plane was in turn connected to the signal ground point. If the filters could not be
mounted on a ground plane or an equipment chassis (which effectively provides a ground plane), extreme care
was taken to provide an adequate case ground. It was recommended that the case of the filter input utilize
shielded cable and that it be connected to the filter via a coaxial type connection with the shield tied to the
case via the connector shell (not via a pigtail). Additionally, a heavy braided ground strap was installed to
connect the filter case to the ground point.
2.4.6 Grounding Precautions. Whenever possible, inadvertent contact to fortuitous conductors in walls or
floors which did not have an adjacent CAA was avoided when installing equipment, cabinets, racks, or ducts.
Moreover, insulators were not utilized unless specifically required, and then only on a case-by-case basis. All
components of the station signal ground distribution system were contained within a CAA or controlled space.
It has been the responsibility of the operating activity to ensure, by periodic inspections, that all areas of the
signal ground system installed in the controlled space meet good engineering practices.
2-61
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