What is the most common source of urban ham radio interference?

Based on aggregated operator reports, switch-mode power supplies are among the most frequently reported sources of urban ham radio interference, often producing broadband noise across multiple HF bands.

Why do LED lights cause so much HF interference?

Many LED drivers use inexpensive switching electronics that generate repetitive noise patterns. In dense urban environments, the cumulative effect of many LED sources can significantly raise the HF noise floor.

Is urban interference worse at night?

Yes. Interference levels often increase during evening hours when lighting, consumer electronics, and chargers are in use, while late-night hours frequently offer a lower overall urban noise floor.

Urban Ham Radio Interference Sources (Statistics)

Ham Radio

By Danny Davis

last updated Thursday, December 19, 2025

About This Data: These statistics represent our analysis of patterns observed across hundreds of publicly reported interference cases in amateur radio forums, technical blogs, and community discussions from 2020–2025. While not from a formal scientific survey, these figures reflect the real-world experience of urban hams and provide the best available quantitative overview of what operators actually encounter. We've aimed to be as accurate as possible while acknowledging this represents estimated distributions rather than laboratory measurements.

Urban and suburban amateur radio operators face a very different RF environment than rural stations. This page documents the most common sources of man-made interference (RFI) reported by hams operating in cities, apartments, and mixed commercial areas — with a focus on HF performance.

The goal is simple: provide practical, cite-able statistics that reflect what operators actually encounter on the air, not theoretical lab conditions.

At-a-Glance Summary

Switch-mode power supplies remain the #1 urban interference source
LED lighting accounts for nearly 1 in 5 reported noise cases
Utility infrastructure dominates severe, wide-area noise events
Consumer electronics rival traditional industrial noise sources

Top Urban Interference Sources (HF)

Rank	Interference Source	Est. Share of Reports	Typical Signature	Bands Affected
1	Switch-Mode Power Supplies (SMPS)	~27%	Broadband hash, steady	80–10m
2	LED Lights & Drivers	~19%	Comb lines every 30–60 kHz	80–20m
3	Power Line / Utility Noise	~15%	Crashing, arcing bursts	160–40m
4	Consumer Electronics	~13%	Wideband, intermittent	80–10m
5	Solar Inverters & Optimizers	~11%	Repeating digital patterns	40–10m
6	Ethernet & Network Cabling	~8%	Narrowband carriers	20–10m
7	Other (HVAC, signage, elevators)	~7%	Mixed	Various

Interference by Operating Environment

Environment	Typical Noise Increase	Most Common Source
Dense Urban (apartments)	+3 to +6 S-units	LED lighting, neighboring electronics
Suburban	+2 to +4 S-units	SMPS, solar installations
Mixed Commercial	+4 to +7 S-units	Utility and industrial equipment
Rural Edge	+1 to +2 S-units	Power lines, farm equipment

Time-of-Day Noise Patterns

Evening (6–11 PM): Highest noise from lighting, TVs, chargers
Daytime: Utility and commercial sources dominate
Late night: Lowest noise floor and best DX conditions

Severity Distribution (HF)

Noise Increase	Est. % of Cases
+1–2 S-units	~34%
+3–4 S-units	~29%
+5–6 S-units	~21%
+7+ S-units	~16%

Most Difficult Interference Sources to Eliminate

Utility power line noise
Neighbor LED lighting
Solar inverter systems
Apartment-wide electrical noise
In-home consumer electronics

Common Mitigation Success Rates

Mitigation Method	Reported Success Rate
Ferrite chokes (multiple turns)	~61%
Replacing noisy power supplies	~54%
Antenna relocation or height change	~47%
Directional receive antennas	~42%
Utility company intervention	~28%

Methodology

These statistics represent our best-effort analysis of real-world interference patterns reported by urban ham radio operators. No formal survey data exists for urban RFI prevalence, so we've synthesized patterns from multiple sources to create this quantitative overview.

Data Sources (2020–2025):

Recurring interference reports on QRZ.com, Reddit's r/amateurradio, and eHam.net forums
Amateur radio club technical bulletins and RFI investigation reports
Individual operator write-ups and mitigation case studies
ARRL RFI documentation and manufacturer technical guidance
Pattern validation against ARRL "Sounds of RFI" audio reference library

Analysis Approach:

We reviewed several hundred documented interference cases and categorized them by source type, characteristic signature, and resolution outcome. Percentages reflect the relative frequency each source type appears in operator reports, not calibrated field measurements.

Limitations: This data represents patterns in reported interference. Some sources may be under-reported (e.g., operators who solve in-home issues quietly) or over-reported (e.g., dramatic utility line failures that generate discussion). Success rates reflect cases where operators reported back with results, which may skew toward more motivated troubleshooters.

Why this matters: While imperfect, this data provides the most comprehensive quantitative overview currently available of what urban hams actually face. It's based on real operator experience, not laboratory theory.

Reference Material & Examples

The following resources were used to help identify and normalize characteristic interference patterns and mitigation approaches:

ARRL Radio Frequency Interference (RFI) Resource Center
ARRL "Sounds of RFI" Audio Samples
Long-running community discussions on QRZ.com, Reddit's r/amateurradio, and amateur radio club mailing lists documenting urban noise investigations
Technical write-ups and mitigation reports from individual operators documenting LED lighting, power supply, and solar inverter interference

How to Cite This Page

Urban Ham Radio Interference Sources (2025), BrokenSignal.tv

Linking to this page helps keep the data current and supports future updates.

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