A browser-based tool for underground mine personnel to document, design, and analyse leaky feeder communication networks. Build schematics of cable segments, amplifiers, splitters, and couplers. Length Mode shows cable run utilisation for electricians; Signal Mode shows dB signal budgets for RF technicians; DC Power mode shows the voltage reaching each amplifier. It is free, needs no account, and keeps several projects side by side with JSON import/export.

How to use it

New to leaky feeders? Press Watch: radio in the rock on the project screen for a three-minute 3D film: a flight into a mine that shows the cable, the head end, loss and amplifiers, splitters, couplers, terminators and DC power, with the same figures the tool uses.

1. On the project screen, press New design…: choose the band, the cable impedance and the radios' transmit power, and start from a head end alone or a template (a decline, a decline and a level, a level with two drives) that already passes every check. Or open the example mine network: the mine in the film, with the five amplifiers, the power supply and the refuge-bay coupler it needs to pass every check. Import a .lfn.json file to continue someone else's design.
2. Add parts from the stencil on the left: a head end, bidirectional amplifiers, 2-way and 4-way splitters, couplers, terminators, DC power sources and antenna nodes that mark coverage zones. Click one, or press its letter (H, A, S, C, T, P), and it is added after the selected part with a cable whose length is ready to type, so A, 350, Enter, A, 350, Enter, T builds a run. You can also drag a part onto the sheet.
3. Right-click a part, a cable or the sheet (or press Shift+F10) to insert a part on a cable, split its length, add after, terminate a branch, change the model or delete. The inspector's Connections block joins and separates parts without a mouse. Parts come from a built-in library of generic and manufacturer-class parts, or you can define your own.
4. Each check in the list says what is wrong and where in one sentence. Where the tool can work out a fix, a button applies it: an amplifier position, for example, is only offered after the tool has checked that it clears the gap.
5. In project settings (System, Thresholds, Display), choose the operating band (VHF or UHF), system impedance, portable radio transmit power, receiver sensitivities, fade margin and the coupling-loss basis (95 % or 50 % of locations). Changes apply as you type, and Undo takes them back.
6. The drawing is a straight-line diagram: the head end on the left, every cable's length to scale along a chainage ruler, branches on lanes below. Under it, the level profile plots the radio level against distance along one path, with both coupling bases as a band. Switch between Length, Signal and DC Power views above the drawing. Each part carries a tag (A1, J1) and a worded status (OK, Marginal, Fails); in Signal view each cable is hatched where coverage is marginal or missing, and numbered balloons match the Checks list on the right. The inspector above it shows the selected part's chainage, details, levels and power, and finds where a TDR distance lands.
7. Open the Print sheet for an issue sheet on A3 or A4: the drawing to scale, the level profile, the level and DC budget, the cable schedule, the bill of materials, notes, revisions and a title block (File › Project details… sets the site, area, drawing number and who drew and checked it). Its commissioning and test sheet lists the expected levels and volts at every amplifier, supply and end, with blank columns for what the crew measures. Choose the paper and what to include, then print it or save it as a PDF.
8. File › Export… downloads the project file (.lfn.json), the drawing as SVG or PNG, and the bill of materials, cable schedule, level and DC budget and test sheet as CSV for a spreadsheet.
9. The Site sheet keeps the network's record. Issue Rev A… freezes the network as a dated revision (design, as built, survey or repair) with a note; any two revisions, or a revision and today's draft, can be compared, with the changes clouded on the drawing and what they did to the levels, the checks and the DC volts listed beside it.
10. Every part and cable has a state: planned, installed, temporary, damaged, bypassed (with the loss of the jumper you fitted) or removed. A damaged or removed one passes no signal and no power, so the drawing and the checks show what lost coverage; View › Count planned parts shows the network with or without what is only planned. The Register lists every part with its serial, dates, approval and owner, and keeps each part's own fault, repair, splice and inspection log.
11. File › Save to file keeps the project file where you choose, so it can travel by email or a shared drive with its revisions and logs. Where the browser allows, later saves write the same file and warn you if it was changed elsewhere; opening a copy of a project you already have merges the two instead of overwriting one.
12. Installed as an app, the tool works with no signal underground: every screen, the film and your projects are on the device, and edits wait there until you are back on the surface. File › Sync… keeps your projects the same on every device through your own Google Drive or OneDrive; when two devices changed the same project, both are kept, the other copy as a revision to compare, never overwritten. File › Share… gives a read-only link (the drawing only, carried inside the link; nothing is uploaded) or the project file, and whoever opens it can save a copy or compare it with theirs.
13. Site › Readings keeps walk tests and DC checks. Plan stops along a route, walk it with a meter, and type each reading: the tool sets it against the predicted level (the 50 % coupling basis, the median), flags any reading more than 6 dB out (you set the tolerance), and where two or more in a row disagree it names the stretch and whatever the record holds there, such as a jumper or a splice.
14. Site › Plan and what if shows, for every branch end, how many metres the cable can still run before the next amplifier is due or coverage runs out, where that amplifier goes, and how many more amplifiers the feeding supply can carry. Extend… lengthens the branch, adds the splices and amplifiers it needs as one undo step, and logs the advance.
15. Settings › Channels lists the channels and services the feeder carries, which sizes each amplifier's multi-carrier load. A fixed antenna can hang off a coupler or splitter on a coax jumper; its level at a stated reach is an indicative free-space figure to confirm with a walk test.
16. Mark refuge chambers, SCSR caches and other strategic places on parts and along cables, and cables that run along an escapeway. Each place is checked at the radio across 61 m (200 ft) either side, the zone MSHA's guidance suggests for strategic areas (you set the zone), and an escapeway must be covered end to end.
17. What if this fails reruns the analysis on a copy with a part failed, a cable cut at a chosen metre, or the mains off, and lists each place as kept, kept on failover or lost; it also lists every single point of failure for each place. A normally-open link (a loop-back) or a second head end on standby is drawn as an alternative feed and analysed as its own tree on failover, naming any amplifier that must be switched to the new direction.
18. A battery on the head end and on each DC supply gives standby hours after a power cut: the derated capacity (20 % held back for ageing unless you set another figure) over the load the engine computes, against a 24 h target (the standby MSHA's guidance calls adequate in many mines; you can change it). A DC supply can feed both ways within its power cell, bounded by DC blocks.
19. Why? beside a level or a voltage in the inspector shows the sum the engine worked through, one line per part, from the head end (or the supply) to that point: each cable as length × loss per 100 m, each amplifier's gain, the coupling loss to a radio 2 m away, then what the figure is judged against and the margin in words ("4.0 dB short"). In Length view a cable's Why? counts its rolls and splices: a roll is how cable arrives, a span is how far the signal can go before an amplifier.
20. Each check's Why? says what it means, why it matters underground and the usual fixes, with the sum behind its figure, and Watch this part opens the film at the scene that explains it; the film's last button brings you back to the check.
21. Help › Help and quick start… covers the first five steps, the three views and the drawing's marks, and holds a glossary of the words the tool uses, each with an example from the film's mine. Each setting says what it is, a typical value and where that value comes from, or that it is assumed.
22. Learn (the tab beside Design and Site, or Learn on the project screen) is a path of twenty-one steps in a sandbox that never touches your drawings: five one-minute hooks where you move something and watch the engine's number move (cable loss, an amplifier's spacing, splitter or coupler, volts along the line, the uplink), seven challenges with a broken network, a move budget and goals the engine checks, four drawings to read (guess where radios go quiet, then check), and Grow a mine: five stages on one mine that grows between them (the decline, a level, a refuge bay, the line sagging, a far heading going quiet on the uplink), each built on the parts you placed in the stages before, ending in Print your mine, which keeps it as a project and opens its print sheet. A solved challenge gives a link that carries no project data, and Keep this as a project copies the sandbox out. Progress stays on this device. The project screen offers three ways in: new to leaky feeder, I install it, I design it.
23. The Map sheet puts the network on your mine plan. Load a plan image for a level, calibrate it from two survey pegs (their eastings and northings, or one distance with north up; a third peg shows how far off it is), trace the drives over it, and pin each part to its drive. A cable whose two ends are pinned gets its length from the plan, measured in 3D along the drives (a decline's slope, not its plan length). The drawing's length never changes by itself: a length check puts the two side by side with what the plan's figure would change, and you choose Use or Keep. Coverage and the numbered checks are drawn along the drives. The plan image stays on this device; the levels, drives and pins sync and share with the drawing, and File › Export… can include the images. On a phone, length checks are in Checks.
24. The 3D sheet walks the mine you traced on Map, at true scale: the drives as rock, the cable on the wall, the parts pinned to it. Choose a drive and walk it with the arrow keys (or hold Walk on on a touch screen); Walk back and Walk on stop at each part, refuge and check. The cable glows by coverage, green where the radio is fine, amber where it is marginal and red where there is none, for downlink or uplink. The strip below says where you are and what is ahead, and the readout gives the radio level the tool predicts at 2 m from the cable. Only what Map traced is drawn: a project with no drives shows the way to Map, and unpinned parts are counted, not guessed into place. On a phone, Open in 3D in a part's sheet walks from that part.

How it works

• Cable loss is attenuation per 100 m × length, plus 0.3 dB per splice. A cable longer than one roll counts the splices it needs. If you set separate downlink and uplink frequencies, each direction gets its own attenuation.
• Amplifiers have fixed gain, or AGC that holds the output at a set point while the needed gain is within range. Above P1dB the amplifier distorts; above its multi-carrier rating it intermodulates. On the uplink a fixed-gain amplifier gives the same gain, and an AGC amplifier makes up the loss of the span before it, unless the part gives its own uplink gain (an assumption). An amplifier with no DC power, or outside the project band, passes no signal.
• Coupling loss is what a signal loses between the cable and a handheld nearby, taken from the cable's datasheet (RFS RADIAFLEX figures, measured by the IEC 61196-4 free-space method) at the 95 % or the 50 % basis, and read as the loss to a radio 2 m from the cable. It counts in both directions.
• Downlink is judged at the radio: the level in the cable minus the coupling loss, compared with the handheld's receiver sensitivity plus a fade margin.
• Uplink is what the head-end receiver hears from a radio at each point: the radio's transmit power, minus the coupling loss, minus the path back (couplers charge their coupling loss on the coupled port, amplifiers add gain), compared with the head-end sensitivity plus the fade margin.
• Headroom is that level minus sensitivity minus fade margin. Below zero the radio works but can fade; below minus the margin it cannot hear.
• Unity gain: each amplifier should make up the loss of the span before it, in both directions. A span that gains or loses more than 3 dB is flagged, because the level creeps up until amplifiers overload, or decays until radios go quiet. Amplifiers in series do not oscillate from this.
• Noise is computed, not capped by an amplifier count: every amplifier adds its noise figure, and on the uplink the noise of all amplifiers on every branch adds up at the head end and raises its effective sensitivity.
• Coverage per cable is the stretch of each cable where a radio meets the margin in both directions, in metres and as a percentage.
• Plan lengths come from the drives you trace, in mine coordinates from the calibration: the shortest way along joined drives between a cable's two pinned ends, in 3D, with an optional allowance for slack (Settings, Units). A difference over 2 m or 2 % of the drawing's length, whichever is larger, is a length check, never a fault, and Use is the only thing that changes the drawing's length.
• Readings are compared with the median (50 %) radio level at the point, from the current design, because one meter reading is a sample around the median. They never change a design verdict.
• Headroom at a branch end is found by laying more cable on a copy of the network and running it through the same engines, so it honours AGC, constant-power draw and DC limits. An amplifier is overdue only when the unity-gain check would flag one placed at the end.
• DC power sums the current drawn downstream (constant power where the part gives watts), calculates the voltage drop (I × R) along each cable, and checks each amplifier's minimum and maximum voltage and each supply's current rating. Past the first amplifier that runs short of voltage, the line has no power. Splitters and couplers can block DC, and any part can draw current.
• Design checks flag amplifier overload, compression and saturation, AGC out of range, spans that are not unity gain, supplies and cables over their current rating, unterminated branches, impedance mismatch, parts outside the project band, parts with no spec, disconnected nodes, a missing or second head end, loops and cables with no length or spec. A cascade limit is an optional rule in the settings.

Questions

Where are my projects stored? In your browser's IndexedDB on this device. Nothing is uploaded. Each change saves on its own, and the toolbar shows when it last saved. Clearing the browser's site data deletes them, so use Export all (backup)… on the project screen now and then; import that file on any computer to bring every project back. Export one project's JSON file to share it with a colleague. If the same project is open in two windows, the tool tells you and lets you choose which version to keep.

Does it work on a phone? Yes, for checking a network in the field and for learning. On a phone an open project is a list you walk from the head end (Route), with the level profile (Profile), the open checks (Checks) and the learn path (Learn). Tap a part or a cable for its levels, a few field edits (label, notes, a cable's length, an amplifier's gain) and a reading you took there; a walk test lists its stops with the level expected at each. Readings are saved on the phone and sync when you have a signal. Building a network (adding and connecting parts) is done on a tablet or a computer: on a touch screen, tap a part in the stencil, then the cable where it goes; press and hold a part or cable for its menu.

Can I rely on it for a compliant design? Treat it as a planning and documentation aid. Library values are generic or typical figures; confirm cable, amplifier and coupler specifications with the manufacturer and verify coverage on site.