Radiating cable design from the first cable choice to coverage across a whole mine: cable selection, amplifier spacing, a multi carrier network model and 3D coverage.
The discipline
A leaky feeder is a coaxial cable built to leak a controlled amount of RF along its length, so it works as an antenna that follows the tunnel instead of a point source that has to fight rock. It remains the dominant radio distribution method in many hard rock and coal mines, and it is used in road and rail tunnels and large buildings wherever an antenna cannot see far enough.
The design is unforgiving because two loss numbers pull in different directions. Longitudinal loss, in dB per 100 m, sets how far the signal travels down the cable and therefore how far apart the amplifiers sit. Coupling loss, quoted at a reference distance from the cable, sets the field where the radio actually is, and it is a fixed penalty at every point along the run. Design to the 95 per cent coupling figure, not the median.
Amplifiers restore the along cable loss but bring limits of their own: a gain ceiling, noise that accumulates down the cascade, and intermodulation once several carriers share the cable. The uplink is often the real limit. A handheld transmits at a fraction of the head end level, pays the full coupling loss to get into the cable, then passes through every amplifier on the way back to the head end, so a healthy downlink does not prove a healthy uplink.
Mine geometry then breaks the assumption that the cable runs in a straight line. Splitters dilute the signal at every junction, and stope accesses and crosscuts without cable are reached only by diffraction around the corner. The tools below follow that order, from one cable run to the whole mine.
The workflow
Start with one passive run, head end to the first amplifier. Enter the frequency, run length, head end power, the minimum level at the radio and the listener distance, and the selector ranks RFS RADIAFLEX and CommScope RADIAX cables by end of run margin at the 50 or 95 per cent coupling figure, filtered to the fire and smoke ratings your site requires.
Do it withLeaky Feeder Cable Selector Free Open the tool →Spacing is the number that sets the amplifier count and the quote. The calculator checks three limits on every segment (the off air level at the radio, the amplifier gain target and the gain ceiling) and names the one that binds. It sizes the inline pad the field technician dials in and prints a landscape commissioning test sheet.
Do it withAmplifier Spacing Calculator Free Open the tool →Build the real topology on a canvas: base stations, combiners, head end, splitters, line and AGC amplifiers, taps and terminations. Every edit reruns a multi carrier simulation with cascaded noise figure, IM3 filtered by each duplexer passband, the DC power feed along the cable, and the uplink budget from each mobile back to the base receiver.
Do it withLeaky Feeder Designer Pro Open the tool →Import the mine centreline from DXF, CSV or KML, or draw it, then route the cable and place splitters and amplifiers. Coverage is shown level by level along every drift in downlink, uplink and worst of link modes, including drifts with no cable, which are reached by ITU-R P.526 corner diffraction and ITU-R P.1238 corridor decay. This tool is in Beta.
Do it with3D Leaky Feeder Coverage Pro Open the tool →Every result here is planning grade. Radiating cable and amplifier performance varies with band, cable family and installation, so design against the actual datasheets and confirm with commissioning measurements.
From other disciplines
Further reading
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