Leaky Feeder Cable Selector

It optimises for end-of-run RSSI margin first, low longitudinal loss second, low coupling loss third, and low cost fourth. The exact weighting is designed so that a cable cannot win by being cheap if it fails the RSSI margin, and cannot win by being low-loss if its coupling is so high that the listener never sees a usable signal at the chosen distance.

Coupling loss is the difference between the signal level inside the radiating cable and the signal level radiated outside it at a reference distance (typically 2 m for RFS, 6 ft / 1.83 m for some CommScope datasheets). Because the slot geometry is periodic and the surrounding environment varies, the radiated level is not constant along the cable — it has a statistical distribution. The 50% value is the median across 100 m sample windows; the 95% value is the level exceeded by 95% of windows. Use 95% for a margin-bounded planning design, and 50% if you are characterising typical performance.

It is a planning-grade single-link estimate. Real coupling loss varies with frequency, slot geometry, tunnel cross-section, cable orientation, near-field versus far-field effects, and reflections from adjacent surfaces. The calculator uses a single log-log interpolated coupling-loss value plus a 20 log₁₀ inverse-distance falloff from the manufacturer reference distance. The number is good enough for sizing decisions and tender estimates; for site-specific coverage prediction with terrain and structure loss the dedicated Leaky Feeder 3D Coverage tool is the right destination, and for amplified Becker chains the Amplifier Spacing Calculator is the right destination.

Cable longitudinal attenuation is dominated by skin-effect (∝ √f) and dielectric loss (∝ f). On a log-log axis the combined curve is close to a straight line in segments. Slotted-cable coupling loss is similarly near-log-linear across the rated band. Linear interpolation in log space produces much better accuracy than linear interpolation in linear space, especially across decade-wide frequency steps.

It depends on the jurisdiction and the application. Rail transit in the US typically requires NFPA 130. European building cables typically require EN 50575 Cca or stricter B2ca for higher-risk spaces. Halogen-free smoke behaviour for indoor public-safety spaces requires IEC 60754-2 plus IEC 61034. Bundled-cable flame performance requires IEC 60332-3-24. US underground coal and hard-rock mining requires MSHA permissibility. The selector lets you tick the union of every standard your project must satisfy and filters out anything that does not carry all of them.

Both are slotted-coax radiating cables with comparable internal construction (solid copper outer with engineered slot patterns, foam dielectric, copper inner). Sizes overlap directly (1/2", 7/8", 1-1/4"). Longitudinal loss differs by a few percent at most. Coupling loss differs by a few dB depending on slot pattern. The biggest practical differences are jacket material (FRNC vs LSZH), fire-rating coverage, declared applications, geographic availability, and price. The selector ranks them side-by-side so the trade-off is visible.

No. Selection and ranking run entirely in your browser. Operating frequency, run length, head-end power, minimum RSSI, listener distance, fire-rating filter, and every other input stay on your machine and are remembered between sessions through browser local storage.

This selector decides which cable to lay. The Amplifier Spacing Calculator decides where to put the Becker / Smart Com line amplifiers along that cable and produces the end-to-end signal trace for an amplified chain. The Leaky Feeder 3D Coverage tool predicts coverage in three dimensions with terrain, tunnel cross-section, and structure loss for site-specific validation. Use them in that order on a typical project.