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Can I modify an FCC-certified product without retesting?

Yes, but it depends entirely on the nature of the change. The FCC allows modified devices to keep their original FCC ID and avoid full retesting under their “Permissive Change” policy (defined in 47 CFR §2.1043), provided the modifications are classified correctly.

The three classes of permissive changes determine your requirements:

1. Class I Permissive Change (No Filing Required)

  • What it covers: Minor modifications, such as changing components (resistors, capacitors) with identical specifications, software updates that do not change RF output power or frequency, or administrative changes like a new model name.
  • Retesting: No.
  • Filing: No new test reports or FCC filings are required. You just need to update your internal compliance records.

2. Class II Permissive Change (Filing Required)

  • What it covers: Modifications that alter the hardware, software, or enclosure but do not degrade performance or fundamentally change the emission characteristics, maximum output power, or frequency range. This includes changing the antenna type or adding co-located transmitters.
  • Retesting: Yes, you generally need to run spot checks or provide test reports of the characteristics affected by the change.
  • Filing: Yes. You must submit test data to the FCC or a Telecommunication Certification Body (TCB) for approval before you can market the modified device.

3. Class III Permissive Change (Filing Required)

  • What it covers: Software modifications for Software-Defined Radios (SDRs) that change the approved frequency range, modulation type, or maximum output power.
  • Retesting: Yes. You must submit test results verifying compliance with the new software.
  • Filing: Yes. This requires FCC/TCB acknowledgment before marketing.

When You Must Apply for a New FCC ID

If your modifications change the fundamental frequency, basic modulation, or increase the maximum output power, the device must undergo full retesting and go through the full certification process as if it were a new product.

To evaluate exactly what your modification requires, review the full scope of the regulations on the FCC Equipment Authorization page.

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