Repeater Planner does not draw pretty range circles. Coverage and links run a link budget over real terrain, then ask whether a receiver at that point still has usable fade. Two terrain engines are available. You do not need the physics paper; you need to know which one to pick and how far to trust the paint.
Slower — Higher Accuracy (ITM), often called Longley-Rice, is the default for coverage and the only engine for site-to-site links. Use it when the map will be briefed, compared to Radio Mobile, or used to argue for a cache order. It takes longer. That is the point. On a clear ground path it also takes the better of ITM and two-ray / free-space (Radio Mobile’s Use two rays). Timber still counts: canopy height stays on the DEM and residual foliage loss still applies. A 2 m handheld in chaparral is not billed an extra ~15 dB “buried in clutter” term — that was ours, not Radio Mobile.
Faster — Generalized (Deygout) respects major ridges and is quick enough to try three candidate pads before the briefing. Reach for it when you are iterating. Do not treat a Deygout sketch as the map you send to a division.
| What you are doing | Engine |
|---|---|
| Quick sketch, many site tries | Faster — Generalized (Deygout) |
| Planning coverage / compare to Radio Mobile | Slower — Higher Accuracy (ITM) |
| Site A to Site B link | ITM (automatic) |
Colors are available fade — signal above the receiver threshold — on both engines. Green is comfortable (about 10 dB of fade and up). Yellow and amber still copy. Purple (or clear mode, if you click the dBm key) is below threshold; clear mode keeps a light fringe tint a few dB under the tick before going blank. That 10 dB is a design comfort target, not a second tax stacked on the color. The same colors drape on the hills in 3D. Reliability (95 / 90 / 80 percent) changes how much fringe you are willing to call usable. Receiver profile matters as much as the engine: a handheld at walking height is a harder test than a mobile on a ridge.
Treat every map as planning grade. Elevation data, antenna and feedline assumptions, foliage, and temporary masts all move the answer more than swapping engines. Major blocked valleys and solid line-of-sight pads should agree with experienced judgment and with Radio Mobile when you match height, power, gains, threshold, and use ITM. Fringe cells and knife-edge near misses are where models argue. Always field-verify before you lock a plan or promise a talk path.
How to run a map: Coverage maps. How to read a hop: Links, point checks, and routes.