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Antennas & RF Guide (868 MHz)

In LoRa mesh networking, your antenna is the single most critical component. An inexpensive $20 radio with a properly tuned antenna will outperform a $100 node with a poorly matched antenna every time.

⚠️ The Stock Antenna Pitfall​

Many budget Chinese boards (Heltec, LilyGO) ship with generic "rubber ducky" antennas:

  • VNA Measurements: In community testing with NanoVNAs, up to 70% of included antennas are resonant at 915 MHz or even 2.4 GHz (Wi-Fi), rather than 868 MHz.
  • VSWR Penalties: A Voltage Standing Wave Ratio (VSWR) higher than 2.5:1 reflects over 20% of your RF power back into the transceiver chip, causing significant heat generation and drastically reducing reception sensitivity.
caution

Always replace or measure your stock antenna with a NanoVNA before deploying critical nodes!

🏆 Recommended 868 MHz Antennas​

1. Handheld & Portable (Everyday Carry)​

  • Gizont 868 MHz 1/4-Wave Whip: Length ~17–19 cm. Consistently demonstrates VSWR < 1.3 across 865–870 MHz.
  • Linx Technologies / TE Connectivity: Commercial-grade whips with exceptional repeatability.
  • Ebyte 868 MHz Flexible Whip: Durable, bendable antenna ideal for backpack loops.

2. Base Station & Repeater Antennas (Rooftops & Peaks)​

  • Fiberglass Omni-Directional 868 MHz (3 dBi to 5.8 dBi):
    • Examples: RAK Wireless Fiberglass Antenna (858–878 MHz) or McGill Microwave 868 MHz.
    • Provides a true 360° toroidal radiation pattern.
    • Weatherproof (IP67), UV-resistant, and wind-rated up to 130 km/h.
Why avoid excessive gain (e.g. 8–12 dBi) in mountainous terrain?

High-gain omnidirectional antennas flatten the radiation pattern into a narrow disc like a pancake. While beneficial over flat plains or open oceans, in mountainous regions like Armenia (where repeaters sit on high peaks looking down into valleys), a narrow beam overshoots targets below. An antenna with 3 dBi to 5.8 dBi provides the ideal balance of range and vertical beamwidth.

🔌 Coaxial Cables & Connectors​

When mounting an antenna away from your node:

  • Avoid RG-58 cable for 868 MHz runs over 2 meters. Signal attenuation at 868 MHz is severe (~0.6 dB/meter on RG58).
  • Use LMR-200 or LMR-400 ultra-low loss coaxial cable.
  • Ensure correct connector polarities: Meshtastic boards almost universally use SMA-Male to SMA-Female connectors, NOT Wi-Fi's RP-SMA (Reverse Polarity).