.. naslov: Friisova prenosna enačba
.. polž: enačba prenosa rf-friis
.. datum: 2025-12-26 15:00:00 UTC
.. oznake: mreženje, kalkulator, orodje
.. kategorija: Kalkulatorji
.. povezava:
.. opis: uporabite Friisovo enačbo prenosa, da poiščete moč sprejetega signala iz moči oddajanja, ojačanja antene in izgube poti. Uporablja se za načrtovanje proračuna RF povezave.
.. vrsta: besedilo
<style>
    .calc-container {
        max-width: 900px;
        margin: 20px auto;
        padding: 20px;
    }

    .calc-header {
        margin-bottom: 30px;
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    }

    .calc-header h2 {
        margin-top: 0;
        color: white;
        font-size: 28px;
        margin-bottom: 10px;
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    .calc-header p {
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        opacity: 0.95;
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    .form-section {
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        gap: 20px;
        margin-bottom: 20px;
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    .form-group {
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    .calc-button {
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        font-size: 16px;
        background: #4CAF50;
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    .calc-button:hover {
        background: #45a049;
        transform: translateY(-1px);
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    .calc-button:active {
        background: #3d8b40;
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    .result-section {
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        transition: all 0.3s ease;
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        margin-top: 30px;
        padding: 20px;
        background: white;
        border-radius: 8px;
        box-shadow: 0 2px 4px rgba(0,0,0,0.05);
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    .help-text {
        margin-top: 15px;
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        border-radius: 4px;
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    /* Responsive design */
    @media (max-width: 768px) {
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</style>
<div class="calc-container">
<div class="calc-header">
<h2>Kalkulator enačb prenosa Friis</h2>
<p>Izračunajte prejeto moč pri brezžičnem prenosu z uporabo Friisove enačbe prenosa. Vnesite frekvenco in razdaljo, da določite izgubo poti v prostem prostoru in polmer Fresnelove cone.</p>
<div class="form-section">
<div class="form-row">
<div class="form-group">
<label for="frequency">Pogostost:</label>
<input autocomplete="off" id="frequency" type="text" value="2.4"/>
</div>
<div class="form-group">
<label for="freunit">Enota frekvence:</label>
<select id="freunit">
<option value="ghz">Gigaherci (GHz)</option>
<option value="mhz">megaherci (MHz)</option>
<option value="khz">Kiloherci (KHz)</option>
<option value="hz">Hertz (Hz)</option>
</select>
</div>
</div>
<div class="form-row">
<div class="form-group">
<label for="distance">Razdalja:</label>
<input autocomplete="off" id="distance" type="text" value="1"/>
</div>
<div class="form-group">
<label for="unit">Enota razdalje:</label>
<select id="unit">
<option value="feet">Miles</option>
<option value="meters">Kilometri</option>
</select>
</div>
</div>
<div class="button-group">
<button class="calc-button" onclick="fresnelZone()" type="button">Izračunaj</button>
</div>
</div>
<div class="help-text">
<strong>Opomba:</strong>Friisova enačba prenosa izračuna moč, ki jo prejme antena v idealiziranih pogojih, če druga antena oddaja znano količino moči, ki je oddaljena nekaj oddaljenosti.</div>
</div>
<div class="result-section" id="resultsSection" style="display: none;">
<div class="section-header">
<h3><span>📡</span>Rezultati izračuna</h3>
</div>
<div class="section-content">
<div class="data-row">
<div class="data-label">Radij Fresnelove cone:</div>
<div class="data-value highlight" id="fnr">-</div>
</div>
<div class="data-row">
<div class="data-label">Središčna točka:</div>
<div class="data-value" id="center">-</div>
</div>
</div>
</div>
<div class="info-section">
<h4>O Friisovi transmisijski enačbi</h4>
<p>Friisova prenosna enačba povezuje moč, ki jo sprejme antena, z močjo, ki jo oddaja druga antena, ki je ločena z določeno razdaljo. Enačba upošteva ojačanja antene in valovno dolžino signala.</p>
<p><strong>Formula:</strong></p>
<p><code>Pr / Pt = Gt × Gr × (λ / 4πR)²</code></p>
<p><strong>kje:</strong></p>
<ul style="margin: 10px 0; padding-left: 20px;">
<li><code>Pr</code>= Moč na sprejemni anteni</li>
<li><code>Pt</code>= Izhodna moč oddajne antene</li>
<li><code>Gr</code>= ojačanje sprejemne antene</li>
<li><code>Gt</code>= ojačanje oddajne antene</li>
<li><code>λ</code>= valovna dolžina</li>
<li><code>R</code>= Razdalja med antenama</li>
</ul>
<p><strong>Fresnelovo območje:</strong>Fresnelovo območje je elipsoidno območje med oddajno in sprejemno anteno. Ta kalkulator izračuna polmer v središčni točki, ki je ključnega pomena za ugotavljanje, ali bodo ovire motile signal.</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>