Electromagnetic forces (EMF) are one of the four fundamental forces in nature, and although they exist naturally, they can also be created. Any wire carrying any amount of electrical current will generate a magnetic field, and any charged conductor will create an electrical field; these two phenomena were once viewed as separate forces, but are now understood to be parts of the larger force described as electromagnetic force. The strength of the magnetic field is proportional to the current passing through the conductor, and the strength of the electrical field is proportional to the voltage potential.
Some devices will have coils of wire, and many will have a permanent magnet or an intentional or situational electromagnet built into their design. In either instance a strong electromagnetic field will be generated. This magnetic field will affect other electrical devices within the sphere of influence of the EMF, and depending on the strength and frequency of the EMF the consequences can be adverse to the point of interference.
Most sensitive electronic devices will provide the appropriate guidelines for installation of the device to be free from the effects of EMF interference from other equipment, but these guidelines maybe difficult to maintain in the confined spaces that are found on many mid-sized boats. In some cases a degree of separation maybe required to avoid interference, and in other cases it may require the installation of a ferrite block to absorb EMF on a line to mitigate adverse effects. In all cases the degree of interference will only become apparent after the devices are placed and become operational. So, whenever possible, pay strict attention to installation guidelines concerning electrical equipment, maintaining wide separation between components, especially those pieces of equipment that are known to be affected by EMF.