Noise and interference
Why is my radio buzzing? The noises in your radio, explained
Most buzzing, hissing and ticking on a radio isn't a signal at all. It's electrical noise from something nearby, and each source has its own sound. Here's how to tell them apart, and how to track one down.
First: is it in the radio, or in the air?
Unplug the antenna, or retract it. If the noise stays just as loud, it may be coming from the radio or its power supply. Try running the radio on batteries. If the noise drops away, it's arriving through the air, and the sections below will help you name it.
The usual suspects, by sound
A harsh, raspy buzz: power-line noise
A rough buzz with a rhythm of 120 pulses a second (100 in countries with 50 Hz power), heard across many frequencies at once, and often worse in dry, windy weather. It usually comes from a loose or failing part on a utility pole: a tiny spark, repeating with every cycle of the power.
A whine or rough tone that repeats as you tune: chargers, LED bulbs and power supplies
Modern power supplies switch on and off tens of thousands of times a second, and cheap ones leak that switching as radio noise. A telltale sign: the same whine or buzz reappears every few kilohertz as you tune, and it may drift as the device warms up.
Noise only in daylight: solar inverters
A comb of tones or a rough buzz that starts in the morning and stops at dusk, following the sun rather than the clock.
A buzzy hash that follows a screen: TVs and displays
If the noise starts and stops when a television or monitor is switched on and off, you've found it.
A steady roar like rushing water over whole stretches of the band: broadband and powerline networking
Blocks of hiss with sharp edges, covering large sections of shortwave. VDSL internet and "powerline" network adapters are common causes.
A pop about once a second: an electric fence
A slow, regular tick or pop, heard across many frequencies, like a metronome. Common in rural areas.
How to find the source at home
- Battery radio walk. Tune a portable radio to a quiet spot (AM between stations works well) and walk around the house. The noise gets louder as you get closer.
- Breaker test. With a battery-powered radio listening, switch your home's breakers off one at a time. When the noise stops, the source is on that circuit. (Mind anything that shouldn't lose power, such as freezers and medical equipment.)
- Unplug and listen. On that circuit, unplug devices one by one. Chargers, LED bulbs, dimmers and power adapters are the most common culprits.
- If it's outside your home, note the times, weather and direction. Power-line noise is usually the utility's to fix, and many utilities have a process for radio-noise complaints.
Is it noise, or a real signal?
Real transmissions usually sit on one frequency and have structure: a rhythm, a set of tones, a start and an end. Noise tends to spread across everything and follow a device, the weather or the time of day. If what you hear has a clear pattern, the field method for identifying signals is the next step.