{
  "id": "glossary:eirp",
  "collection": "glossary",
  "slug": "eirp",
  "name": "EIRP / ERP",
  "summary": "Transmitter power multiplied by antenna gain: the figure that, with distance, determines free-space power density.",
  "status": "verified",
  "lastVerified": "2026-08-12",
  "data": {
    "definition": "Equivalent isotropically radiated power is the power an isotropic radiator would need to produce the same field on the antenna's main beam. ERP is the same idea referenced to a half-wave dipole (ERP × 1.64 = EIRP). Both describe the main beam only, so using EIRP with an inverse-square formula gives a boresight upper bound and overstates exposure everywhere off-axis — which is why levels at the base of a tower are far below the value the formula suggests.",
    "category": "technology",
    "seeAlso": [
      "emitters:macro-cell-tower",
      "quantities:power-density"
    ]
  },
  "sources": [
    {
      "id": "fcc-oet65",
      "title": "OET Bulletin 65: Evaluating Compliance with FCC Guidelines for Human Exposure to Radiofrequency Electromagnetic Fields",
      "publisher": "Federal Communications Commission, Office of Engineering and Technology",
      "url": "https://www.fcc.gov/general/oet-bulletins-line",
      "year": 1997,
      "kind": "government",
      "retrieved": "2026-08-12"
    },
    {
      "id": "itu-fs-relations",
      "title": "Free-space path loss and power density relations (ITU-R P.525)",
      "publisher": "International Telecommunication Union",
      "url": "https://www.itu.int/rec/R-REC-P.525/en",
      "kind": "standard",
      "retrieved": "2026-08-12"
    }
  ],
  "links": {
    "self": "https://emfbase.com/api/glossary/eirp",
    "html": "https://emfbase.com/glossary/eirp",
    "markdown": "https://emfbase.com/glossary/eirp.md",
    "collection": "https://emfbase.com/api/glossary"
  }
}