Cable Length & Signal Attenuation Calculator
ANA›Life Services Authority›National Calculator Authority›Cable Length & Signal Attenuation Calculator
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Cable Length & Signal Attenuation Calculator
Calculate signal attenuation (signal loss) over a given cable length based on cable type, frequency, and cable specifications.
Cable Type
Custom (enter attenuation coefficient) RG-58 Coaxial RG-59 Coaxial RG-6 Coaxial RG-11 Coaxial Cat5e (UTP) Cat6 (UTP) Cat6a (UTP) Single-Mode Fiber (SMF) Multi-Mode Fiber (MMF)
Frequency (MHz)
Cable Length
Meters Feet Kilometers
Attenuation Coefficient (dB/100m)
Input Signal Power (dBm) (optional)
Leave blank to calculate attenuation only.
Number of Connectors / Splices
Loss per Connector / Splice (dB)
Calculate
// Attenuation data: [dB/100m at reference freq MHz, frequency exponent k] // Model: alpha(f) = alpha_ref * (f / f_ref)^k [dB/100m] // Sources: manufacturer datasheets, TIA/EIA-568 standards const CAB_CABLE_DATA = { rg58: { name: "RG-58 Coaxial", alpha_ref: 6.6, f_ref: 100, k: 0.5, f_min: 1, f_max: 1000, connector_default: 0.5 }, rg59: { name: "RG-59 Coaxial", alpha_ref: 5.6, f_ref: 100, k: 0.5, f_min: 1, f_max: 1000, connector_default: 0.5 }, rg6: { name: "RG-6 Coaxial", alpha_ref: 4.5, f_ref: 100, k: 0.5, f_min: 1, f_max: 1000, connector_default: 0.5 }, rg11: { name: "RG-11 Coaxial", alpha_ref: 2.4, f_ref: 100, k: 0.5, f_min: 1, f_max: 1000, connector_default: 0.5 }, cat5e: { name: "Cat5e UTP", alpha_ref: 22.0, f_ref: 100, k: 0.59, f_min: 1, f_max: 100, connector_default: 0.1 }, cat6: { name: "Cat6 UTP", alpha_ref: 19.8, f_ref: 100, k: 0.59, f_min: 1, f_max: 250, connector_default: 0.1 }, cat6a: { name: "Cat6a UTP", alpha_ref: 20.9, f_ref: 100, k: 0.59, f_min: 1, f_max: 500, connector_default: 0.1 }, smf: { name: "Single-Mode Fiber (SMF)",alpha_ref: 0.035, f_ref: null, k: null, f_min: null, f_max: null, connector_default: 0.1, fixed: true, note: "~0.35 dB/km at 1310nm; 0.2 dB/km at 1550nm. Using 0.035 dB/100m." }, mmf: { name: "Multi-Mode Fiber (MMF)", alpha_ref: 0.35, f_ref: null, k: null, f_min: null, f_max: null, connector_default: 0.2, fixed: true, note: "~3.5 dB/km at 850nm. Using 0.35 dB/100m." }, };
function cabUpdateCableType() { const type = document.getElementById('cab-cable-type').value; const freqRow = document.getElementById('cab-freq-row'); const attenRow = document.getElementById('cab-atten-coeff-row'); const hint = document.getElementById('cab-coeff-hint'); const connLoss = document.getElementById('cab-connector-loss');
if (type === 'custom') { freqRow.style.display = 'none'; attenRow.style.display = ''; document.getElementById('cab-atten-coeff').value = ''; hint.textContent = ''; connLoss.value = '0.5'; return; }
const d = CAB_CABLE_DATA[type]; connLoss.value = d.connector_default;
if (d.fixed) { freqRow.style.display = 'none'; attenRow.style.display = ''; document.getElementById('cab-atten-coeff').value = d.alpha_ref.toFixed(4); hint.textContent = d.note || ''; } else { freqRow.style.display = ''; attenRow.style.display = ''; hint.textContent = 'Auto-calculated from frequency using ' + d.name + ' model.'; cabUpdateAttenCoeff(); } }
function cabUpdateAttenCoeff() { const type = document.getElementById('cab-cable-type').value; if (type === 'custom') return; const d = CAB_CABLE_DATA[type]; if (!d || d.fixed) return;
const f = parseFloat(document.getElementById('cab-frequency').value); const hint = document.getElementById('cab-coeff-hint'); if (isNaN(f) || f d.f_max) { hint.textContent = 'Warning: frequency outside typical range (' + d.f_min + '–' + d.f_max + ' MHz) for ' + d.name + '.'; } else { hint.textContent = 'Auto-calculated for ' + d.name + ' at ' + f + ' MHz.'; } const alpha = d.alpha_ref * Math.pow(f / d.f_ref, d.k); document.getElementById('cab-atten-coeff').value = alpha.toFixed(4); }
function cabToMeters(val, unit) { if (unit === 'ft') return val * 0.3048; if (unit === 'km') return val * 1000; return val; }
function cabCalc() { const resultDiv = document.getElementById('cab-result'); resultDiv.innerHTML = '';
const lengthVal = parseFloat(document.getElementById('cab-length').value); const lengthUnit = document.getElementById('cab-length-unit').value; const attenCoeff = parseFloat(document.getElementById('cab-atten-coeff').value); const inputPower = document.getElementById('cab-input-power').value.trim(); const numConn = parseInt(document.getElementById('cab-connectors').value) || 0; const connLoss = parseFloat(document.getElementById('cab-connector-loss').value) || 0;
// Validation const errors = []; if (isNaN(lengthVal) || lengthVal 0) { resultDiv.innerHTML = 'Input Error:' + errors.map(e => '').join('') + ''; return; }
const lengthM = cabToMeters(lengthVal, lengthUnit); const lengthKm = lengthM / 1000;
// Total cable attenuation: alpha [dB/100m] * length[m] / 100 const cableAtten = attenCoeff * (lengthM / 100);
// Connector/splice loss const connectorAtten = numConn * connLoss;
// Total attenuation const totalAtten = cableAtten + connectorAtten;
// Output power (if input provided)
let powerSection = '';
if (inputPower !== '') {
const pIn = parseFloat(inputPower);
const pOut = pIn - totalAtten;
const pInW = Math.pow(10, pIn / 10) * 0.001;
const pOutW = Math.pow(10, pOut / 10) * 0.001;
const pInMw = pInW * 1000;
const pOutMw = pOutW * 1000;
powerSection = **Input Power**${pIn.toFixed(2)} dBm (${pInMw.toExponential(3)} mW)
**Output Power**${pOut.toFixed(2)} dBm (${pOutMw.toExponential(3)} mW)
**Power Ratio (out/in)**${(pOutMw/pInMw * 100).toFixed(4)}%;
}
// Max length for given max attenuation budgets
const budgets = [3, 6, 10, 20];
let budgetRows = '';
if (attenCoeff > 0) {
budgets.forEach(b => {
const maxLenM = (b / attenCoeff) * 100;
budgetRows += ${b} dB budget${maxLenM.toFixed(1)} m / ${(maxLenM/0.3048).toFixed(1)} ft / ${(maxLenM/1000).toFixed(3)} km;
});
}
const cableTypeEl = document.getElementById('cab-cable-type'); const cableLabel = cableTypeEl.options[cableTypeEl.selectedIndex].text; const freqVal = document.getElementById('cab-frequency').value; const freqDisplay = (freqVal && document.getElementById('cab-freq-row').style.display !== 'none') ? freqVal + ' MHz' : 'N/A';
resultDiv.innerHTML = ` ### Results
Cable Type${cableLabel} Frequency${freqDisplay} Cable Length${lengthVal} ${lengthUnit} (${lengthM.toFixed(2)} m / ${lengthKm.toFixed(4)} km) Attenuation Coefficient${attenCoeff.toFixed(4)} dB/100m (${(attenCoeff10).toFixed(4)} dB/km) Cable Attenuation${cableAtten.toFixed(4)} dB Connector/Splice Loss${numConn} × ${connLoss} dB = ${connectorAtten.toFixed(4)} dB Total Signal Attenuation*${totalAtten.toFixed(4)} dB ${powerSection}
${budgetRows ? `#### Maximum Cable Length for Common Attenuation Budgets
BudgetMax Length (cable only)${budgetRows}: ''};
}
// Initialize cabUpdateCableType();
#### Formulas Used
Cable Attenuation:
Acable = α × L / 100
Where α = attenuation coefficient [dB/100m], L = cable length [m].
Frequency-Dependent Coefficient (Coaxial & Twisted Pair):
α(f) = αref × (f / fref)k
Where αref is the reference attenuation at fref, and k ≈ 0.5 (coaxial, skin-effect dominated) or ≈ 0.59 (twisted pair, per TIA-568).
Total Attenuation:
Atotal = Acable + Nconn × Aconn
Output Power:
Pout [dBm] = Pin [dBm] − Atotal [dB]
P [W] = 10(P[dBm] / 10) × 0.001
#### Assumptions & References
- Coaxial cable attenuation follows a square-root frequency dependence (skin effect): α ∝ f0.5 (Pozar, Microwave Engineering).
- Twisted-pair (Cat5e/6/6a) attenuation uses exponent k = 0.59 per TIA/EIA-568-C.2 standard.
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