Choosing the Right Modem Preset

The modem preset is the single most impactful LoRa setting — it determines range, data rate, and network capacity. This page provides a decision framework for choosing the right preset for your deployment.

Step 1: Ask Your Community First

Before anything else: what does your local mesh network use? Ask on the community Discord, check meshmap.net, or contact local operators. Using a different preset isolates your node from the existing community network. This is the most important step.

Step 2: If Building a New Network — Choose by Size

Sparse / Rural Networks (under 30 nodes in range)

Use Long Fast (the Meshtastic default). At low node density, network capacity is not a concern. Maximizing range ensures the widest possible coverage from each node. Long Fast provides excellent range while keeping data rate high enough for reasonable message latency.

Medium-Density Networks (30-60 nodes)

Consider Medium Slow or Medium Fast. At this density, Long Fast's airtime per packet starts contributing to congestion, especially with position telemetry from many nodes. The 3-4x faster data rate of Medium presets reduces airtime dramatically while maintaining similar range in most terrain.

Dense Urban Networks (60+ nodes)

Use Medium Slow or faster. Several large community networks (Bay Area Meshtastic: 150+ nodes; Wellington, NZ: 150+ nodes) have successfully migrated from Long Fast to Medium Slow and report significant reliability improvements. At 100+ nodes, Long Fast's ~1 second airtime per packet creates constant background congestion; Medium Slow's ~0.25 second airtime provides 4x more capacity.

Preset Selection Matrix

Migrating a Network to a Different Preset

Changing presets on an active community network requires careful coordination:

1. Announce the planned change at least 1 week in advance
2. Document the exact new preset value
3. Schedule a cutover time (e.g., Sunday midnight when traffic is lowest)
4. Have all operators change their nodes simultaneously
5. Verify connectivity after the change
6. Update all network documentation with the new preset

Nodes that don't update in time will be invisible to the network until their operator updates. Plan for 2-4 weeks of dual-operation where some users are still on the old preset.