Coaxial Cable Loss Calculator
Compute total dB loss of a coaxial cable: length × attenuation per meter. For RF, specific frequency, cable type (RG-58, RG-213, etc.).
Coaxial cable loss: attenuation in dB per length
Coaxial cable attenuation is usually tabulated in dB per 100 m (or per 100 ft) at a reference frequency, and grows with frequency due to the skin effect and dielectric loss. For a length L at frequency f the total loss is LdB = α(f) · L. Reference numbers: RG-58 ≈ 5 dB/100 m at 100 MHz; RG-213 ≈ 1.5 dB/100 m; RG-6 ≈ 1.8 dB/100 m at 100 MHz (≈10 dB/100 m at 1 GHz); LMR-400 ≈ 1.0 dB/100 m. Example: 20 m of RG-58 at 100 MHz → 20 × 0.05 = 1 dB of loss, equivalent to ≈21% power drop. Compared with optical fibre (≈0.2 dB/km at 1550 nm), coax loses thousands of times more — that is why long-distance backbones are fibre, not copper.
Applications: antenna feeds, cable TV, DOCSIS broadband, broadcasting
Cable-loss calculations guide antenna sizing (keep the run between antenna and radio as short as possible), cable-TV plant design (in-line amplifiers compensate for loss), DOCSIS broadband, broadcast telecom and laboratory RF where the link budget must close.
FAQ
Why does loss grow with frequency? The skin effect forces current to the conductor surface, raising effective resistance; dielectric losses also rise with frequency.
How much loss is acceptable? Rule of thumb: keep total loss under 3 dB (≈50% power) — above that, choose a thicker cable or shorten the run.
Does an amplifier solve the problem? It compensates the loss but also amplifies noise; better to reduce the loss first (shorter run, better cable).
Fibre versus coax? Fibre loses ≈0.2 dB/km vs ≈50 dB/km on coax at the same frequency — fibre dominates for long distances.
Related Tools
Prestress Friction Loss
Calculate the prestress force loss from friction along a curved tendon, ΔP = P_0·(1 − e^(−(μα + k·x))), from the jacking force P_0 (kN), the tendon-duct friction coefficient μ, the sum of tendon deviation angles α (radians), the wobble coefficient k (loss per metre, 1/m) and the tendon length x (m). In POST-TENSIONING (where the tendon is tensioned after the concrete hardens, sliding inside a duct embedded in the member), the force applied at the end by the jack does NOT arrive full at the other end: FRICTION between tendon and duct consumes part of it along the path. There are two effects: friction in the tendon CURVES (μα term — the more the tendon curves, the more it 'squeezes' the duct and the greater the friction, like a rope on a pulley — the capstan effect) and 'wobble' friction in straight runs (k·x term — from small undulations and duct misalignment). Friction loss makes the prestress force DECREASE progressively from the active end (jack) to the passive (dead anchorage), which is why long tendons are sometimes tensioned from BOTH ends. It is an immediate loss, computed tendon by tendon. Enter the jacking force, friction coefficient, sum of angles, wobble coefficient and length.
Wire Rope Safety Factor
Calculate a wire rope's safety factor, SF = breaking load ÷ working load, from the minimum breaking load (MBL, N) and the applied working load (N). Wire ropes, used in cranes, elevators, cableways, bridges, lifting and mooring, work with HIGH safety factors — far higher than static structures — for several reasons: the load is rarely static (there are impacts, accelerations, swings), the rope wears and loses strength over use (wires break, corrosion and fatigue occur), and a rupture is catastrophic (load drop, life risk). Codes prescribe minimum safety factors per application: typically 5 for general load lifting, 6-8 for people-carrying ropes (elevators, cableways), 3-4 for static stays and moorings, and specific values per use. The safety factor is the ratio between the load that would break the rope (its rated strength, from the maker) and the load it actually carries in service. Checking that the real safety factor meets the code minimum is the basic safety check of any wire-rope application — and the rope must be DISCARDED when wear reduces its strength enough for the factor to fall below the limit. Enter the breaking load and the working load.
Tunnel Volume Loss
Calculate the volume loss of a tunnel excavation, VL = Vs ÷ (π·D²/4)·100, the percentage ratio between the settlement trough volume per metre Vs (m³/m) and the excavated cross-section area (from diameter D). Volume loss quantifies how much soil 'disappeared' relative to the theoretical tunnel volume — caused by face relaxation, overexcavation, tail-gap closure behind the TBM shield and consolidation. It is the key control parameter for urban excavation: well-run EPB/slurry TBMs achieve 0.5-1.5% in soils; values above 2-3% indicate problems and excessive settlement. Enter the trough volume and the tunnel diameter.
Hoist Rope Tension
Calculate the resultant force in an elevator's hoist rope, F = (Q + M_car − M_counterweight)·g, from the payload Q, the car mass and the counterweight mass (kg). The result, in newtons, is the unbalanced effort the steel ropes must transmit, already net of the counterweight's balancing effect. It is the basis for sizing the ropes (number, diameter and safety factor, typically ≥ 12 in elevator codes) and the traction sheave. When the load is such that car + load ≈ counterweight, the force tends to zero (balanced system). Enter the load, the car mass and the counterweight mass.
Hydraulic Jump Energy Loss
Calculate the specific energy dissipated in a hydraulic jump, ΔE = (y₂ − y₁)³ ÷ (4·y₁·y₂), from the upstream y₁ (supercritical) and downstream y₂ (subcritical) sequent depths. The hydraulic jump is one of the most efficient energy dissipators in hydraulics: intense turbulence in the transition converts kinetic energy to heat and sound, removing excess flow energy. This head loss ΔE is exactly what is sought downstream of spillways, gates and bottom outlets — water arrives with very high energy (able to scour the riverbed and undermine the structure), and the stilling basin induces the jump to 'burn' that energy in a controlled way. The higher the incoming Froude number, the greater the dissipated fraction — jumps with Fr > 9 dissipate up to 85%. Enter the upstream and downstream sequent depths.
Elastic Shortening Loss
Calculate the prestress loss from concrete elastic shortening, Δσ = (E_s/E_c)·σ_c, from the steel modulus E_s (MPa), the concrete modulus E_c (MPa) and the concrete stress at the tendon level σ_c (MPa). It is one of the IMMEDIATE prestress losses (at transfer, not over time): when the tendon is tensioned and anchored, it compresses the concrete, and the concrete, being compressed, SHORTENS elastically. Since the tendon is bonded or anchored in this shortened concrete, it shortens too — and shortening, it LOSES part of its tension. The loss is proportional to the modular ratio αe = E_s/E_c (typically 6-8, since steel is much stiffer than concrete) times the concrete compression stress at the tendon level. In members with SEVERAL tendons prestressed sequentially, each new tendon compresses and shortens the concrete, causing loss in already-anchored tendons — so the average loss is often taken as half the value (the first tendons lose more than the last). This is one of the losses to subtract from the initial force to get the effective prestressing force. Enter the steel and concrete moduli and the concrete stress.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.