What causes interference received as a series of carriers at regular intervals across a wide frequency range?

Interference that appears as a series of carriers spaced at regular intervals across the spectrum is a classic symptom of a noisy switch-mode power supply (SMPS). These power supplies operate by rapidly switching current on and off, usually at frequencies between 20 kHz and hundreds of kilohertz. If they are poorly filtered or lack proper shielding, this fast switching generates strong, repetitive harmonics. Because the fundamental switching frequency is constant, the harmonics appear on your receiver as distinct 'birdies' or carriers evenly spaced by that exact switching frequency (e.g., every 50 kHz) across a wide range of bands. Other options, like radar or electric fences, produce rhythmic popping or clicking noises, not steady carriers.