High-Power Mountain Repeater Build (~$200)
High-Power Mountain Repeater Build (~$200)
This build is designed for demanding deployments —- mountain summits, ridge lines, or any site that needs extended range and the ability to survive winter conditions. It pairs a LilyGO T-Beam with a 1–1 - 2W power amplifier module, a LiFePO4 battery bank, and a robust MPPT charge controller.
Parts List
| Part | Approx. Cost |
|---|---|
| LilyGO T-Beam v1.1 (ESP32 + SX1276/SX1262 + GPS + 18650 holder) | ~$35 |
| ZebraHat 1W power amplifier board or Ikoka 2W RF amplifier module | ~$ |
| 10W 12V monocrystalline solar panel | ~$20 |
| Genasun GVB-8 or Victron SmartSolar 75/10 MPPT charge controller | ~$ |
| LiFePO4 battery, 12V 10Ah | ~$45 |
| Fibox TEMPO 11×9×5" weatherproof enclosure | ~$30 |
| LMR-200 low-loss coax, 1m + N-type connectors (crimped or soldered) | ~$15 |
| 6 dBi fiberglass omni antenna, N-type, 915 MHz | ~$25 |
| Mounting hardware (J-pipe mount, stainless U-bolts, mast) | ~$20 |
| Total | ~$ |
Key Design Considerations
Power Amplifier & Heat Management
The ZebraHat and Ikoka modules both require a 12V supply rail (taken directly from the LiFePO4 battery or a regulated 12V bus). At 1W continuous TX duty, the amplifier dissipates roughly 3W as heat. Mount the amplifier board against an aluminum bracket that contacts the enclosure wall, or add a small heatsink with thermal paste. Without adequate thermal management, output power will derate and long-term reliability will suffer.
EIRP & Regulatory Compliance
Combining a 1W (30 dBm) amplifier with a 6 dBi antenna produces 36 dBm EIRP —- right at the FCC Part 15 limit for unlicensed 915 MHz operation. Confirm the antenna gain rating is measured (not marketing-inflated). If you hold an amateur radio license (Technician or above), you can operate at higher power levels under Part 97, but you must use an open protocol and identify by callsign.
LiFePO4 Chemistry for Cold Deployments
LiPo cells lose up to 50% capacity at 0°C and must not be charged below freezing. LiFePO4 cells retain ~80% capacity at -20°C and can be safely charged down to -10°C (with a BMS that supports low-temperature charge cutoff). For any deployment above 1500m elevation or at latitudes above 40°N, LiFePO4 is strongly recommended over LiPo.
Winter Solar Harvest
A 10W panel mounted at a 30° south-facing tilt at 45°N latitude delivers approximately 15–15 - 20 Wh/day at winter solstice. The system draws roughly 5W peak (1W RF + ESP32 + GPS) and much less on average with duty-cycling. This yield is sufficient for a 24/7 repeater with a 10Ah battery providing overnight and multi-day overcast reserves.
Coax Loss Matters at 1W
RG58 loses approximately 2.5 dB per meter at 915 MHz. LMR-200 loses only ~0.9 dB/m. At 1W transmit power with a 1m run, switching from RG58 to LMR-200 recovers ~1.6 dB —- equivalent to nearly 45% more effective radiated power. Always use LMR-200 or better for the final run to the antenna when transmitting at elevated power levels.
Assembly Overview
- Mount the MPPT controller and LiFePO4 battery in the lower half of the Fibox enclosure using DIN rail or bracket mounts.
- Connect the solar panel input to the MPPT controller following the manufacturer's polarity labeling. Connect the battery output terminals.
- Wire a 12V regulated output from the MPPT load terminals to the ZebraHat/Ikoka amplifier input and to a 5V step-down converter powering the T-Beam.
- Stack the ZebraHat onto the T-Beam GPIO headers (or connect via short SMA pigtail if using the Ikoka module). Thermal-pad the amplifier to the enclosure wall.
- Run LMR-200 from the amplifier RF output through a weatherproof N-type bulkhead in the enclosure wall. Terminate with an N-type connector
—- do not use SMA at this power level. - Attach the 6 dBi fiberglass antenna to the external N-type bulkhead. Wrap the connector joint with self-amalgamating tape.
- Flash and configure firmware (see below), then seal the enclosure with silicone RTV on all penetrations.
- Mount the enclosure on the J-pipe mast with stainless U-bolts. Orient the solar panel to true south at the appropriate tilt angle for your latitude.
Firmware Configuration
Flash the T-Beam with either Meshtastic (broader community compatibility) or MeshCore repeater firmware depending on your network's protocol stack.
- Set TX power to
27–27 - 30 dBm at the modem level. The amplifier adds its gain on top—- verify total EIRP against the regulatory limit. - Disable the OLED display after configuration to save ~20 mA continuously.
- Disable Bluetooth after initial setup (reduces attack surface and saves ~5 mA).
- Set a fixed GPS position manually once the site coordinates are known, then disable live GPS polling to save ~20 mA and extend GPS module life. Use a smartphone app on-site to capture precise coordinates before sealing.
- Set the node role to Repeater / Router and disable any hop-limit reduction that would prevent the node from forwarding distant packets.