.. titolo: Friis Transmission Equation
.. slug: rf-friis-transmisio-ekvacio
.. dato: 2025-12-26 15:00:00 UTC
.. etikedoj: retigado, kalkulilo, ilo
.. kategorio: Kalkuliloj
.. ligo:
.. priskribo: Apliku la Friis-dissendekvacion por trovi ricevitan signalpotencon de elsendpotenco, antengajnon kaj padperdon. Uzita por RF-liga buĝeta planado.
.. tajpu: tekston
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</style>
<div class="calc-container">
<div class="calc-header">
<h2>Friis Transmission Equation Calculator</h2>
<p>Kalkulu la ricevitan potencon en sendrata dissendo uzante la Friis-transsendan ekvacion. Enigu la frekvencon kaj distancon por determini la liberspacan vojon perdon kaj Fresnel-zonradiuson.</p>
<div class="form-section">
<div class="form-row">
<div class="form-group">
<label for="frequency">Ofteco:</label>
<input autocomplete="off" id="frequency" type="text" value="2.4"/>
</div>
<div class="form-group">
<label for="freunit">Frekvenca unuo:</label>
<select id="freunit">
<option value="ghz">Gigaherco (GHz)</option>
<option value="mhz">Megaherco (MHz)</option>
<option value="khz">Kiloherco (KHz)</option>
<option value="hz">Hertz (Hz)</option>
</select>
</div>
</div>
<div class="form-row">
<div class="form-group">
<label for="distance">Distanco:</label>
<input autocomplete="off" id="distance" type="text" value="1"/>
</div>
<div class="form-group">
<label for="unit">Distanca unuo:</label>
<select id="unit">
<option value="feet">Miles</option>
<option value="meters">Kilometroj</option>
</select>
</div>
</div>
<div class="button-group">
<button class="calc-button" onclick="fresnelZone()" type="button">Kalkuli</button>
</div>
</div>
<div class="help-text">
<strong>Notu:</strong>La Friis dissenda ekvacio kalkulas la potencon ricevitan per anteno sub idealigitaj kondiĉoj donita alian antenon iom for elsendante konatan kvanton de potenco.</div>
</div>
<div class="result-section" id="resultsSection" style="display: none;">
<div class="section-header">
<h3><span>📡</span>Kalkulaj Rezultoj</h3>
</div>
<div class="section-content">
<div class="data-row">
<div class="data-label">Fresnel-Zona Radiuso:</div>
<div class="data-value highlight" id="fnr">-</div>
</div>
<div class="data-row">
<div class="data-label">Centra Punkto:</div>
<div class="data-value" id="center">-</div>
</div>
</div>
</div>
<div class="info-section">
<h4>Pri la Friis Transmisio-Ekvacio</h4>
<p>La Friis dissenda ekvacio rilatigas la potencon ricevitan per anteno al la potenco elsendita per alia anteno, apartigita per iom da distanco. La ekvacio respondecas pri antengajnoj kaj la ondolongo de la signalo.</p>
<p><strong>Formulo:</strong></p>
<p><code>Pr / Pt = Gt × Gr × (λ / 4πR)²</code></p>
<p><strong>Kie:</strong></p>
<ul style="margin: 10px 0; padding-left: 20px;">
<li><code>Pr</code>= Potenco ĉe la ricevanta anteno</li>
<li><code>Pt</code>= Eliga potenco de elsenda anteno</li>
<li><code>Gr</code>= Gajno de la ricevanta anteno</li>
<li><code>Gt</code>= Gajno de la elsenda anteno</li>
<li><code>λ</code>= Ondolongo</li>
<li><code>R</code>= Distanco inter antenoj</li>
</ul>
<p><strong>Fresnel-zono:</strong>La Fresnel-zono estas elipsoida regiono inter la elsendaj kaj ricevantaj antenoj. Ĉi tiu kalkulilo komputas la radiuson ĉe la centra punkto, kio estas kritika por determini ĉu malhelpoj malhelpos la signalon.</p>
</div>
</div>
<script>
/**
 * Friis Transmission Equation Calculator
 * Calculates Fresnel zone radius based on frequency and distance
 *
 * Equation:
 * Pr / Pt = Gt × Gr × (Lambda / 4 × Pi × R)²
 *
 * Where:
 * - Pr: Power at the receiving antenna
 * - Pt: Output power of transmitting antenna
 * - Gr: Gain of the receiving antenna
 * - Gt: Gain of the transmitting antenna
 * - Lambda: Wavelength
 * - R: Distance between antennas
 *
 * Fresnel Zone Calculation:
 * For Miles: radius = 72.05 × √(d1 × d2 / f)
 * For Kilometers: radius = 17.32 × √(d1 × d2 / f)
 * Where d1 and d2 are distances from each antenna to the center point
 */

'use strict';

function fresnelZone() {
    // Get input values
    const frequency = Number(document.getElementById("frequency").value);
    const freunit = document.getElementById("freunit").value;
    const distance = Number(document.getElementById("distance").value);
    const unit = document.getElementById("unit").value;

    // Validate inputs
    if (isNaN(frequency) || frequency <= 0) {
        alert("Please enter a valid frequency greater than 0");
        return;
    }

    if (isNaN(distance) || distance <= 0) {
        alert("Please enter a valid distance greater than 0");
        return;
    }

    // Convert frequency to GHz
    let sf;
    if (freunit === "ghz") {
        sf = frequency;
    } else if (freunit === "mhz") {
        sf = frequency / 1000;
    } else if (freunit === "khz") {
        sf = frequency / 1000000;
    } else {
        sf = frequency / 1000000000;
    }

    // Calculate center point (halfway)
    const d1 = distance / 2;
    const d2 = d1;

    // Calculate Fresnel zone radius based on unit
    let radius, distunit;
    if (unit === "feet") {
        // For miles: radius in feet
        radius = Math.round(36.03 * Math.sqrt(distance / sf));
        distunit = "Miles";
    } else {
        // For kilometers: radius in meters
        radius = Math.round(8.657 * Math.sqrt(distance / sf));
        distunit = "Kilometers";
    }

    // Display results
    document.getElementById("fnr").innerHTML = radius + " feet";
    document.getElementById("center").innerHTML = "The center of the Fresnel Zone is " + d1 + " " + distunit + " from the first antenna.";

    // Show results section
    document.getElementById("resultsSection").style.display = "block";

    // Scroll to results
    document.getElementById("resultsSection").scrollIntoView({ behavior: 'smooth', block: 'start' });

    console.log(`Calculation complete: Frequency=${sf}GHz, Distance=${distance}${distunit}, Radius=${radius}ft`);
}

// Add enter key support for inputs
document.addEventListener('DOMContentLoaded', function() {
    console.log('Friis Transmission Equation Calculator initialized');

    // Allow Enter key to trigger calculation
    const inputs = document.querySelectorAll('#frequency, #distance');
    inputs.forEach(input => {
        input.addEventListener('keypress', function(e) {
            if (e.key === 'Enter') {
                fresnelZone();
            }
        });
    });

    // Auto-focus first input
    document.getElementById('frequency').focus();
});
</script>