drawings.  The  shield  and  connector  shell  should  be electricaly connected and properly secured at either end  interconnecting  cables  may  have  to  be  routed through  spaces  where  a  potential  for  EMI  exists  (such as radar rooms). Cables for digital equipments and audio should never be run in the same cableways as cables carrying  rf  signals  or  high-power-pulse  cables.  The shielding  protects  the  data  and  voice  cables  from  EMI to a great extent. (This is only true if the cable is properly assembled and carefully routed to avoid strong EMI fields.) POWER  SOURCE.–  Power  lines  for  electronic and digital equipment can provide a transmission path for  EMI  from  machinery  spaces.  Most  input  power passes through noise elimination filters as it enters the equipment.  Failure  of  power  line  filters  (actually bandpass/band reject falters) is rare but happens on occasion.  Unusual  random  problems  in  equipment  can sometimes be traced to defective line falters. Unusually large transient voltages on power lines may also cause EMI. The easiest way to check this type of problem is with an oscilloscope, an isolation capacitor, and a 10:1 probe. Connect the probe and capacitor in series with the main power deenergized. Apply power and check the scope to determine if excessive noise or “hash” is riding on the input voltage. CAUTION:  Always  observe  all  safety  pre- cautions while checking equipment input power. Shorebased EMI Control Control of EMI at a shorebased installation requires the consideration of the same factors as for a shipboard system, with two additional factors: site location and soil quality. These two factors may contribute to the generation of  additional  EMI.  They  are  discussed  in  the  following paragraphs. SITE  LOCATION.–  Shorebased  electronic  and digital data equipment sites are sometimes built where the need dictates or where a convenient building is available. Such sites often are not ideal. A site built near a large industrial complex, such as a shipyard or a naval aviation depot, may be subject to severe EMI. There can also be power line fluctuations if the shore site and the industrial  complex  have  the  same  power  source.  In addition, a large amount of EMI is generated by any welding that may take place in the nearby facility. Special  precautions  may  be  needed  if  sensitive electronic and digital data equipment are located at sites near  a  high-noise  industrial  facility.  For  example, shielding may be needed around an especially sensitive piece of equipment to ensure its proper operation. Additional line falters and regulators for power lines may  be  needed  to  reduce  EMI  and  provide  line  power within   the   limits   prescribed   by   equipment manufacturers. SOIL QUALITY.–  At  shorebased  installations,  a system-ground  bus  is  normally  attached  to  a grounding rod driven into the soil. If the soil is dry, sandy,  rocky  soil,  such  as  that  found  in  the Southwestern  United  States  and  some  places overseas,  the  ground  will  be  poor.  (Soil  that  is  not ordinarily  a  good  conductor  must  be  chemically treated to increase its conductivity.) In some cases, a poor  ground  may  act  like  an  antenna.  The  ground cable  can,  under  these  conditions,  provide  an  EMI potential in excess of 5 volts between itself and the power ground. You can check a suspect system ground with   an   oscilloscope   and   a   1:1   probe.   Using power-line ground as a reference, connect the tip of the probe to thes system ground, and the shield of the probe to the power ground. An excessive amount of noise  displayed  on  the  oscilloscope  may  indicate  a system-ground problem. EMI  SURVEYS EMI surveys are conducted to distinguish which equipment is affected and to determine the extent of interference.  An  EMI  survey  is  required  for  new construction ships and for ships receiving overhauls or other   major   repair   work   that   changes   the electromagnetic  configuration.  As  a  senior  ET,  you should also request that an EMI survey be conducted if you experience interference on your equipments that you and others are unable to trace to a malfunction in your own equipment. The  EMI  survey  must  be  well  planned  and coordinated to ensure optimum use of dockside and underway  test  time.  Refer  to  MIL-STD-1605,  Military Standard-Procedures   for   Conducting   a   Shipboard Electromagnetic  Interference  (EMI)  Survey  (Surface Ships) for more detailed information on EMI surveys and reports. 2M  PROGRAM Increased  equipment  complexity,  miniaturization, microminiaturization, and the current high tempo of operational requirements have placed an increasing burden on maintenance personnel and facilities. These 8-5