Overview

In some installations, amateur radio operators or other radio users may report radio frequency interference (RFI) that appears across one or more frequency bands. While a solar inverter can be a potential source of electromagnetic emissions, interference can also originate from installation-related factors such as cabling, grounding, antenna systems, connectors, or other electronic equipment located nearby.

A structured investigation is essential to accurately identify the source and determine the most effective corrective actions.

Typical Symptoms

Reported symptoms may include:

• Broadband noise visible across multiple amateur radio bands
• Audible noise on radio receivers
• Reduced reception quality or signal-to-noise ratio
• Interference present on multiple antennas
• Noise levels that change when PV generation starts or stops

The appearance of interference alone does not automatically confirm that the inverter is the source.

Initial Verification

Before investigating the inverter itself, it is important to verify when and how the interference occurs.

Recommended questions include:

• Which frequency bands are affected?
• Is the interference present during the day, night, or both?
• Does the noise level correlate with inverter operation or PV production?
• What type of noise is observed (broadband noise, periodic pulses, tones, beeps, etc.)?
• Is the interference visible on a spectrum analyzer or Software Defined Radio (SDR)?
• Are multiple radio systems affected?

The answers can provide valuable clues regarding the actual source.

Installation Factors to Review

Many EMC-related issues originate from installation characteristics rather than equipment defects.

Antenna System

The radio installation should be reviewed, including:

• Antenna type being used
• Antenna location relative to the inverter and PV wiring
• Feedline routing
• Coaxial cable type and condition
• Connector quality and shielding performance

Poor shielding, damaged connectors, or antenna feedlines routed close to power cables can increase susceptibility to interference.

Common Mode Currents

One of the most common causes of RFI complaints is common mode current travelling on antenna feedlines or other conductors.

Checks may include:

• Installation of common mode chokes on coaxial feedlines
• Verification of antenna baluns where applicable
• Inspection of grounding and bonding arrangements
• Review of cable routing to minimise coupling between RF and power circuits

Grounding and Bonding

Proper grounding and equipotential bonding are critical for EMC performance.

Verify:

• Protective earth continuity
• PV frame grounding where required
• Bonding of metal structures
• Compliance with local electrical regulations

Customer Testing Already Performed

In some cases, customers may already have tested several mitigation measures, including:

• Ferrite cores on AC cables
• Ferrite cores on DC strings
• Ferrite cores on communication cables
• Additional mains EMC filters
• Operating radio equipment from batteries to eliminate conducted interference through the radio power supply

If these actions produce no measurable improvement, additional investigation is usually required before conclusions can be drawn.

Additional Diagnostic Measurements

To help identify the source of interference, the following information may be useful:

SDR or Spectrum Analyzer Screenshots

Wideband spectrum captures before and after inverter startup can help identify patterns and affected frequencies.

Time Correlation Testing

Observe whether interference:

• Starts when the inverter powers up
• Changes with output power
• Disappears when PV production stops
• Remains present even when the inverter is inactive

Distance Testing

Measure noise levels at different distances from:

• The inverter
• AC cabling
• DC cabling
• Communication cables

A significant change in signal strength can help identify the emission source.

Antenna Relocation Testing

Temporary relocation of antennas can help determine whether the issue is caused by local coupling effects rather than equipment emissions.

Could This Indicate an Inverter Hardware Issue?

In rare cases, abnormal emissions may indicate an equipment fault or degraded EMC performance. However, this conclusion should only be reached after installation-related causes have been thoroughly investigated.

Factors that may warrant further engineering review include:

• Emissions significantly above expected levels
• Interference affecting multiple frequency ranges
• No change after installation improvements
• Reproducible results across different installations
• Evidence from spectrum measurements supporting the inverter as the primary source

Engineering teams may request additional measurements, photos, spectrum captures, installation diagrams, and operating data to support further analysis.

Best Practice

When investigating EMC or RFI concerns, the most effective approach is to evaluate the complete system rather than focusing on a single component. Antennas, cable routing, grounding arrangements, connectors, communication wiring, and the surrounding RF environment can all influence observed interference levels.

A systematic troubleshooting process increases the likelihood of identifying the true source and implementing an effective solution.

Safety and Compliance Notice

Electrical work, testing, inspection, and modifications should only be carried out by qualified electrical professionals in accordance with local regulations and safety requirements. Failure to follow proper procedures may result in personal injury, equipment damage, communication issues, or loss of warranty coverage.