Why Height Matters
The single most important factor in Meshtastic node placement is height above local terrain. More than hardware, more than antenna gain, more than transmit power — how high your antenna sits above the surrounding obstacles determines how far your node can reach. This is not a guideline. It’s physics.
The Radio Horizon
Radio waves at 868 MHz travel in almost straight lines. They don’t follow the Earth’s curve. This means two radios at ground level, separated by buildings, hills, or any solid obstacle, cannot communicate directly — the terrain blocks the signal.
The radio horizon — the distance at which signals disappear over the Earth’s curvature, ignoring obstacles — is calculated as:
d = 4.12 × √h (kilometres)Where h is the antenna height in metres above the surrounding terrain.
| Height AGL | Radio Horizon | Typical Scenario |
|---|---|---|
| 1.5m (pocket) | ~5 km | Hand-held in a field |
| 10m (rooftop) | ~13 km | Flat suburban rooftop |
| 25m (steeple) | ~21 km | Church tower in a village |
| 42m (cathedral) | ~27 km | St Giles’, Edinburgh |
| 60m (telecom mast) | ~32 km | Roadside mast |
This is the horizon for one side of the link. For two nodes communicating, the horizons add together. A 42m cathedral tower talking to another 25m steeple: up to 48km theoretical range in clear conditions, covering a substantial slice of central Scotland.
The Key Insight: AGL, Not ASL
AGL (above ground level) is what matters. ASL (above sea level) is almost irrelevant.
A Meshtastic node on a hillside at 300m ASL, tucked into a valley below the ridgeline, may have an effective radio horizon of a few hundred metres in most directions — because it’s looking at walls of hillside. A node on a church tower in a market town at 50m ASL, with 25m of steeple above the rooftops, can see for 20+ km in every direction.
This is why we focus on built structures — church towers, water towers, telecom masts, estate buildings on high ground. A structure you can drive to, connect mains or solar power to, access for maintenance, and mount hardware on with landowner permission delivers reliable, year-round coverage.
Scotland’s Built Infrastructure
Scotland is full of elevated structures that already exist above local skylines:
- Church towers and steeples at 20–50m AGL in virtually every town and village
- Water towers on elevated ground at the edge of settlements
- Telecom masts at road junctions and on high ground
- Estate buildings — shooting lodges, farm steadings — on elevated terrain
- Community and civic buildings — town halls, schools, fire stations — with accessible rooftops
A node mounted on St Giles’ Cathedral in Edinburgh sits at 42m above the Royal Mile. It has clear line of sight over the rooftops of central Edinburgh in every direction. That single structure, properly equipped, could serve as a backbone node for the entire city and beyond.
Link Budget and Practical Range
A link budget calculates whether two radios can communicate by accounting for:
- Transmit power (typically 25mW = 14 dBm)
- Antenna gain (a good external antenna adds 3–6 dBi)
- Path loss (signals weaken with distance, roughly 20 dB per decade of distance)
- Receiver sensitivity (Meshtastic devices: typically -137 dBm)
- Fade margin (buffer for conditions: 10–20 dB)
A standard Meshtastic device on the long-range/slow spreading factor has a link budget of around 157 dB. In free space (perfect conditions), that allows links of 100+ km. In a city, buildings cost you dB. This is exactly why elevation above the local skyline is so transformative — it removes the building loss entirely by putting the node above the obstacles.
A node on a church steeple at 25m AGL, cleared above the rooftops, effectively has free-space propagation in every direction. The same device on the pavement below the same church sees nothing but walls.
The Practical Rule
For Meshtastic Scotland, our deployment principle is: if your node sits above the local skyline in multiple directions, it extends the network meaningfully.
We deploy deliberately. A structure you can drive to, service in an afternoon, power from mains or a reliable solar setup, and maintain with the landowner’s ongoing support is what a durable network is built from. Height from structures, not height from sea level.
Antenna Choice
Elevation is the biggest lever — but antenna choice matters too. The standard rubber duck antenna that comes with most LoRa devices is adequate for hand-held use. For a fixed structure deployment, you want better:
- Fiberglass vertical (e.g., 868 MHz 6dBi antenna): adds 6 dB of gain, increases effective range substantially
- Weatherproof enclosure: essential on any exposed structure — moisture and freeze-thaw cycles destroy electronics
- Sealed cable gland: antennas mounted through the enclosure wall need a proper weatherproof gland
A properly weatherproofed node with a 6dBi external antenna on a modest church tower will consistently outperform a bare module at much higher altitude. Both the AGL height and the antenna quality matter — and structures let you do both right.