EMC and the 20-meter band

Most of the complaints of interference from amateur radio operation in the United States and Canada involve only a few of the many bands authorized to this radio service. The bands most commonly involved are the popular DX bands at wavelengths of 15 and 20 m. The interference from these bands is almost entirely common-mode on the house wiring due to the close correspondence of wiring to resonant lengths at 14 an 21 MHz. The theoretical aspects of the problem are treated in detail and the mathematical description of the problem is derived. It is felt that any devices for electrical protection from such interference should be installed at the victim site.<
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