.. tittel: RF Fresnel Zone Kalkulator
.. slug: rf-fresnel-sone
.. dato: 2025-12-26 15:00:00 UTC
.. tags: nettverk, kalkulator, verktøy, RF, trådløst
.. kategori: Kalkulatorer
..lenke:
.. beskrivelse: Beregn Fresnel-sonens radius for trådløse RF-koblinger for å sikre riktig signalutbredelse
.. type: tekst
<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;
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        .data-label {
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</style>
<div class="calc-container">
<div class="calc-header">
<h2>RF Fresnel Zone Kalkulator</h2>
<p>Beregn Fresnel-sonens radius for trådløse RF-koblinger. Fresnel-sonen er et elliptisk område rundt den visuelle siktebanen som radiobølger sprer seg ut i etter at de har forlatt antennen.</p>
<div class="input-grid">
<div class="input-group">
<label for="frequency">Hyppighet:</label>
<div class="input-row">
<input id="frequency" placeholder="Enter frequency" type="text" value="2.4"/>
<select id="freunit">
<option value="ghz">GHz</option>
<option value="mhz">MHz</option>
<option value="khz">KHz</option>
<option value="hz">Hz</option>
</select>
</div>
</div>
<div class="input-group">
<label for="distance">Avstand:</label>
<div class="input-row">
<input id="distance" placeholder="Enter distance" type="text" value="1"/>
<select id="unit">
<option value="feet">Miles</option>
<option value="meters">Kilometer</option>
</select>
</div>
</div>
</div>
<button class="calc-button" onclick="fresnelZone()">Beregn Fresnel-sonen</button>
</div>
<div class="result-section" id="results">
<div class="section-header">Beregningsresultater</div>
<div class="section-content">
<div class="data-row">
<div class="data-label">Fresnel soneradius:</div>
<div class="data-value highlight" id="fnr">-</div>
</div>
<div class="data-row">
<div class="data-label">Sentrumspunkt plassering:</div>
<div class="data-value" id="center">-</div>
</div>
</div>
</div>
<div class="info-box">
<h3>Om Fresnel Zones</h3>
<p>
<strong>Hva er en Fresnel-sone?</strong>Fresnel-sonen er et elliptisk område rundt den visuelle siktebanen mellom to antenner. Radiobølger sprer seg mens de reiser, og denne sonen representerer området der disse bølgene kan forstyrre konstruktivt eller destruktivt.</p>
<p>
<strong>Hvorfor er det viktig?</strong>For optimal RF-linkytelse bør minst 60 % av den første Fresnel-sonen være fri for hindringer (bygninger, trær, terreng). Denne kalkulatoren hjelper deg med å bestemme den nødvendige klaringsradiusen ved midtpunktet av den trådløse koblingen.</p>
<p>
<strong>Slik bruker du:</strong>Angi driftsfrekvensen og den totale avstanden mellom antennene. Kalkulatoren vil vise deg radiusen til Fresnel-sonen på det bredeste punktet (sentrum av lenken).</p>
</div>
</div>
<script>
function fresnelZone() {
    // Set variables from input
    var frequency = Number(document.getElementById("frequency").value);
    var freunit = document.getElementById("freunit").value;
    var distance = Number(document.getElementById("distance").value);
    var unit = document.getElementById("unit").value;

    if (freunit == "ghz") {
        var sf = frequency;
    } else if (freunit == "mhz") {
        var sf = frequency/1000;
    } else if (freunit == "khz") {
        var sf = frequency/1000000;
    } else {
        var sf = frequency/1000000000;
    }


    var d1 = distance / 2;
    var d2 = d1;
    if (unit == "feet") {
        //var radius = Math.round(72.05 * Math.sqrt((d1*d2/(sf))));
        var radius = Math.round(36.03 * Math.sqrt((distance/sf)))
        var distunit = "Miles"
    } else {
        //var radius = Math.round(17.32 * Math.sqrt((d1*d2/(sf))));
        var radius = Math.round(8.657 * Math.sqrt((distance/sf)))
        var distunit = "Kilometers"
    }

    document.getElementById("fnr").textContent = radius + " feet";
    document.getElementById("center").textContent = "Located " + d1 + " " + distunit + " from the first antenna";

    // Show results section
    document.getElementById("results").classList.add("show");

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

// Add enter key support
document.addEventListener('DOMContentLoaded', function() {
    document.getElementById("frequency").addEventListener('keypress', function(e) {
        if (e.key === 'Enter') {
            fresnelZone();
        }
    });

    document.getElementById("distance").addEventListener('keypress', function(e) {
        if (e.key === 'Enter') {
            fresnelZone();
        }
    });
});
</script>