7. Radio interference

There are two main types: impulse and regular. Impulsive or parasitic disturbances are mainly due to poorly protected domestic or industrial equipment, such as commutator electric motors or internal combustion engines (QRM). To these we can add stormy atmospheric disturbances, such as static discharges and lightning (QRN). Trans-horizon HF radars also generate such interference.

Regular interference is caused by emissions that are too wide-band due to incorrect equipment settings, poorly eliminated harmonic frequencies, intermodulation products or emissions that are too close to the one received. Occasionally, exceptional propagation phenomena can lead to the reception of unusual emissions that can cause interference, particularly in television, where two transmitters can be received on the same channel, each interfering with the other. Their duration is limited....