Antennas, range and power
The antenna is the single most important factor for LoRa range. A better antenna improves both transmit distance and receive sensitivity.
Antenna Types
| Type | Gain | Pattern | Best For |
|---|---|---|---|
| Stub / rubber duck | 0-2 dBi | Omnidirectional | Included with boards, basic testing |
| 1/4 wave ground plane | 2-3 dBi | Omnidirectional | Fixed stations, simple to build |
| Collinear | 5-8 dBi | Omnidirectional | Fixed stations, best all-around coverage |
| Yagi | 8-15 dBi | Directional | Point-to-point links, maximum range |
| Dipole | 2 dBi | Omnidirectional | Compact, good for indoor/portable |
Frequency Matching
Your antenna must be tuned for your operating frequency:
| Band | Antenna Label |
|---|---|
| 433 MHz | 433 MHz antenna |
| 868 MHz | 868 MHz or 900 MHz antenna |
| 915 MHz | 915 MHz or 900 MHz antenna |
Warning: Never transmit without an antenna connected. Operating a LoRa radio with no antenna (or a mismatched antenna) can permanently damage the radio module.
Connectors
Most RNode-compatible boards use SMA or U.FL/IPEX connectors:
- SMA - larger, threaded, more durable. Common on T-Beam, LoRa32.
- U.FL / IPEX - tiny snap-on connector on smaller boards. Use a U.FL-to-SMA pigtail for external antennas.
Range by Terrain
| Scenario | Typical Range | Notes |
|---|---|---|
| Urban, indoor | 0.5-2 km | Buildings absorb signal heavily |
| Urban, rooftop | 2-10 km | Line-of-sight helps significantly |
| Suburban | 5-15 km | Mix of clear and obstructed paths |
| Rural, flat terrain | 10-30 km | Near line-of-sight |
| Hilltop to hilltop | 20-50+ km | Clear line-of-sight, elevation advantage |
| Mountain peak | 50-100+ km | Extreme range with directional antennas |
What Improves Range
- Higher antenna placement (elevation is the single biggest factor)
- Higher-gain antenna
- Clear line-of-sight to target
- Higher TX power (up to legal limits)
What Reduces Range
- Buildings, trees, and terrain between nodes
- Indoor placement
- Antenna mismatched to frequency
For spreading factor and bandwidth trade-offs, see LoRa Radio Interfaces.
Transmit Power
TX power is set in dBm (decibels relative to 1 milliwatt):
| dBm | Milliwatts | Use Case |
|---|---|---|
| 2 | 1.6 mW | Very short range, battery saving |
| 7 | 5 mW | Short range, low power |
| 10 | 10 mW | Moderate range |
| 14 | 25 mW | Fast preset |
| 17 | 50 mW | Balanced preset |
| 20 | 100 mW | Near maximum |
| 22 | 160 mW | Maximum for most boards |
Doubling TX power adds only ~3 dB (marginally more range). Improving your antenna or raising its height is almost always more effective than increasing power.
Regulatory Compliance
LoRa operates on ISM bands (Industrial, Scientific, Medical) - unlicensed but regulated:
| Region | Band | Key Rules |
|---|---|---|
| US (FCC) | 915 MHz | Power/channel rules apply; duty-cycle limits are not the usual constraint |
| EU (ETSI) | 868 MHz | Sub-band duty-cycle limits apply; configure conservative airtime caps |
| EU | 433 MHz | Duty cycle limits apply |
For EU 868 MHz, Ratspeak's default region metadata uses conservative airtime caps:
airtime_limit_long = 1.5
airtime_limit_short = 33
When configured, Reticulum rate-limits transmissions against those caps. That helps, but it does not replace checking the exact sub-band, antenna gain, and power rules for your country.
Warning: Verify the legal frequency band and power limits for your country before transmitting. ISM bands are unlicensed but usage rules vary by jurisdiction.
Optimizing Your Setup
For maximum range: mount a collinear or Yagi antenna as high as possible, set TX power to the maximum legal limit, and ensure clear line-of-sight. Use a long-range LoRa preset. See LoRa Radio Interfaces for preset details.
For best throughput: use a fast LoRa preset and accept shorter range in exchange for ~11 Kbps. Good for local networks where range is not the priority.
For battery life: use the lowest TX power that maintains your connection, disable WiFi on Ratdeck/rsCardputer when not needed, and use a balanced or fast preset to minimize airtime per packet.