{
    "title": "EH Antenna",
    "inventor_name": "Ted Hart",
    "publication_year": 2003,
    "device_name": "EH Antenna",
    "goal": "Provide a very small but efficient antenna suitable for limited space (e.g., attic) while maintaining acceptable performance for amateur radio bands.",
    "problem_addressed": "Conventional half-wave dipoles require large physical dimensions; many users lack space for full-size antennas.",
    "concept_summary": "The EH antenna consists of two tubular (or conical) conductive plates separated by a dielectric (PVC). The electric field is generated by voltage across the plates, and the magnetic field by displacement current in the dielectric. By arranging the E- and H-fields at right angles and in phase within a compact volume, a high radiation resistance (~2368 Omega) is achieved. A balanced L-network (two inductors and two capacitors) matches the antenna to a 50-Omega feed line.",
    "detailed_description": null,
    "category": "Antennas & RF Systems",
    "principles": [
        "Crossed-field generation",
        "Impedance matching",
        "Resonant radiation resistance"
    ],
    "scientific_domains": [
        "Electromagnetism",
        "RF Engineering"
    ],
    "mechanisms_of_action": [
        "Voltage across conductive plates creates an electric field",
        "Displacement current in the dielectric creates a magnetic field",
        "Balanced L-network transforms 50 Omega feed to high radiation resistance"
    ],
    "materials": [
        "PVC plumbing tube",
        "tin-plated steel fruit cans",
        "copper wire",
        "capacitors",
        "inductors",
        "self-tapping screws",
        "rubber bands"
    ],
    "energy_sources": [
        "Radio-frequency transmitter power (e.g., 10 W)"
    ],
    "inputs": [
        "RF feed line (50 Omega unbalanced)",
        "Adjustable inductance and capacitance values"
    ],
    "outputs": [
        "Radiated electromagnetic waves (20 m and 40 m amateur bands)"
    ],
    "claimed_performance": "Radiation resistance ~=2368 Omega; SWR can be tuned to ~1:1; signal strength only a few S-points below a full-size inverted-V; can light a small fluorescent lamp with <15 W input.",
    "experimental_evidence": "Author built 20 m and 40 m units, measured inductance/capacitance, achieved low SWR, and reported on-air performance compared with an inverted-V antenna.",
    "replication_status": "Two prototype units (20 m and 40 m) were constructed and tested by the author.",
    "keywords": [
        "EH antenna",
        "compact dipole",
        "crossed field",
        "matched network",
        "amateur radio"
    ],
    "related_technologies": [
        "Crossed Field Antenna (CFA)",
        "Magnetic Transmitting Loop"
    ],
    "controversy_level": "low",
    "confidence_score": 0.9,
    "practicability_score": 0.8,
    "fringe_score": 0.2,
    "evidence_strength": 0.6,
    "risk_score": 0.1,
    "trl_estimate": 5,
    "source_urls": [
        "http://www.eh-antenna.com",
        "http://www.eh-antenna.com/library/Theory%20of%20the%20EH%20and%20HZ%20Antennas.pdf",
        "http://www.eh-antenna.com/library/EH_ANTENNA_FOR_HAMS.pdf",
        "http://www.eh-antenna.com/library/EH_ANTENNA_DEFINITION.pdf",
        "http://www4.tpgi.com.au/ldbutler"
    ],
    "organizations": [
        "Amateur Radio Journal"
    ],
    "applications": [
        "Amateur radio transmission and reception",
        "Shortwave communication where space is limited"
    ],
    "limitations": [
        "Weather durability - tin-plated cans corrode without protection",
        "Potential magnetic distortion from ferromagnetic steel cans",
        "Performance still modest compared with full-size dipole"
    ],
    "open_questions": [
        "How does the ferromagnetic nature of steel cans affect the H-field?",
        "Would copper tubing significantly improve efficiency?",
        "Optimal cylinder length-to-diameter ratio for various bands"
    ],
    "red_flags": [],
    "evidence_quotes": [
        "Radiation Resistance (RL) is given as equal to 2pi x 377 = 2368 ohms.",
        "When adjusted, I could light up a small BC fluorescent lamp from the field around the dipole with less than 15 watts.",
        "On transmitting on 40 metres to stations in the local Adelaide metropolitan area, reports gave the signal down around two S points on the inverted V.",
        "The EH dipole was just barely below the inverted V on 20 metres at 1500 km distance.",
        "The antenna can be tuned up at the centre of the band and operated across the band without retuning."
    ]
}