# Repeater Density and Coverage Calculations

How many repeaters do you need, and where should they go? This page provides practical calculation methods for MeshCore network coverage planning.

## Link Budget Basics

The maximum range between two MeshCore nodes depends on the link budget:

```
Link Budget = TX Power + TX Antenna Gain + RX Antenna Gain - Feedline Loss - Path Loss

Example (typical repeater setup):
TX Power: +22 dBm (158 mW - legal limit for USA ISM)
TX Antenna: +5 dBi (fiberglass omni)
RX Antenna: +5 dBi (fiberglass omni)
Feedline Loss: -1 dB each end = -2 dB total
Path Loss at 5 km free space: ~108 dB at 915 MHz
Receiver Sensitivity (SX1262, SF9): -125 dBm

Available fade margin:
(22 + 5 + 5 - 2) - 108 - (-125) = 47 dB fade margin

Real-world adjustment (buildings, terrain): -10 to -20 dB
Net fade margin: 27-37 dB - solid link
```

## Terrain Effects on Range

Free-space calculations assume line of sight. Real-world path loss modifiers:

<table id="bkmrk-environmenttypical-r"><thead><tr><th>Environment</th><th>Typical Range (equal-height nodes)</th><th>Range (one node elevated 30m)</th></tr></thead><tbody><tr><td>Flat open terrain</td><td>3-8 km</td><td>10-20 km</td></tr><tr><td>Suburban (low buildings)</td><td>1-3 km</td><td>5-10 km</td></tr><tr><td>Dense urban (high-rise)</td><td>0.3-1 km</td><td>2-5 km</td></tr><tr><td>Forest/jungle</td><td>0.5-2 km</td><td>2-5 km</td></tr><tr><td>Mountainous (valley-to-peak)</td><td>Variable</td><td>20-50 km (ridge-to-ridge)</td></tr></tbody></table>

## Coverage Area Calculation

For a given expected range R, a single omnidirectional repeater covers approximately:

```
Coverage area = pi * R^2

At R = 3 km: ~28 km^2 (~11 sq miles)
At R = 5 km: ~78 km^2 (~30 sq miles)
At R = 10 km: ~314 km^2 (~121 sq miles)
```

These are theoretical maximums. Actual coverage is typically 50-70% of the theoretical circle due to terrain, buildings, and RF absorption.

## Repeater Density Guidelines

For a network where most clients are within 1 hop of a repeater:

- **Urban dense (Manhattan, downtown Chicago):** 1 repeater per 0.5-1 km^2 (500m radius)
- **Suburban:** 1 repeater per 3-8 km^2 (1-1.5 km radius)
- **Rural flat terrain:** 1 repeater per 20-50 km^2 (2.5-4 km radius)
- **Rural with elevation advantages:** 1 repeater per 50-200 km^2 (4-8 km radius)

These are starting points. After initial deployment, use the actual RSSI/SNR data from your node database to identify coverage holes and place additional repeaters strategically.

## Path Hop Analysis

In MeshCore, messages travel via discovered paths. The path length (hop count) determines:

- **Latency:** ~100-500ms per hop in normal conditions
- **Reliability:** Each hop adds failure probability; a 5-hop path with 95% per-hop reliability = 77% end-to-end delivery probability

Target: most clients should reach the room server within 3 hops. 5+ hops indicates a coverage gap that a new repeater could address.