text: Operating in a Contested Environment
  Communications Jamming
  A-25. Radio operators must learn to recognize and react to electromagnetic jamming. This is not always an
  easy task, since electromagnetic interference can be either internal or external. Other sources having nothing
  to do with enemy jamming may cause electromagnetic interference. Unintentional electromagnetic
  interference may be caused by one or more of—
  * Other radios (friendly and enemy).
  * Other electronic, electrical, or electromechanical equipment.
  * Atmospheric conditions.
  * Equipment malfunction.
  A-26. Radio operators must train to quickly differentiate between internal and external interference. Refer
  to ATP 6-02.53 for more information about isolating and eliminating internal sources of interference.
  A-27. Electromagnetic jamming most commonly affects single-channel radio systems. These radios
  include HF, VHF, and UHF radios. Jamming effects may be obvious or subtle. Obvious jamming is normally
  simple to detect. When experiencing jamming, it is more important to recognize and overcome the incident
  than to identify it formally.
  A-28. Subtle jamming is less obvious because subtle jamming signals produce no sound from the receivers.
  Although everything may appear normal to the radio operator, the receiver cannot receive an incoming
  friendly signal. Often, users assume their radios are malfunctioning, instead of recognizing subtle jamming.
  Table A-1 on page A-6 lists some common jamming signals.