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 Fast or Medium Slow. At this density, Long Fast's airtime per packet starts contributing to congestion, especially with position telemetry from many nodes. Medium presets carry data faster (Medium Fast is about 3x quicker than Long Fast, Medium Slow about 2x), which reduces airtime while maintaining similar range in most terrain.

Dense Urban Networks (60+ nodes)

Use Medium Fast or Medium Slow. Some large community networks have reported success migrating away from Long Fast to faster presets - for example, the Bay Area Group (150+ nodes) moved to Medium Slow, and the Wellington Region Mesh in New Zealand migrated its mesh to Short Fast - and report reliability improvements. At high node counts, a full-length Long Fast packet (SF11/BW250) occupies roughly 1-2 seconds of airtime, creating constant background congestion; faster Medium presets cut airtime substantially and free up channel capacity. Actual airtime depends on payload size - a small (~50 byte) Long Fast packet is roughly 400-700 ms.

Preset Selection Matrix

Note: Long Turbo's 150 dB link budget is essentially the same as Medium Slow (150.5 dB) and below Long Fast (153 dB). It trades Long-Fast range for a higher data rate by using 500 kHz bandwidth, so treat its coverage as Medium-tier, not Long-tier. (Long Turbo's status as a current firmware enum should be confirmed against the firmware protobuf.)

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.