Meshtastic 433 MHz Retranslator Node — Build Guide

Overview

A solar-powered, tree-mounted Meshtastic relay node operating on 433 MHz (EU_433 region). Designed for 6+ km coverage radius from an elevated forest hilltop position.

Parameter	Value
Frequency	433 MHz (EU_433)
Modem preset	LONG_SLOW
Device role	ROUTER
Target range	6–10 km radius
Power	Solar + LiPo battery
Mounting	Tree-top, above canopy

System Block Diagram

graph TD
    SOLAR["☀️ 5V 6W USB Solar Panel"]
    USB["USB-A to USB-C Cable"]
    HELTEC["Heltec LoRa 32 V3.1\n433 MHz\nESP32-S3 + SX1262"]
    BATT["3.7V LiPo Battery\n3000–6000 mAh\nSH1.25-2P connector"]
    IPEX["IPEX/U.FL to SMA\nPigtail 15 cm"]
    BULK["SMA Bulkhead\non Enclosure Wall"]
    ANT["433 MHz Antenna\nGround Plane or\nFiberglass Collinear\n2.5–5 dBi"]

    SOLAR -->|"5V USB"| USB
    USB -->|"USB-C"| HELTEC
    BATT -->|"SH1.25"| HELTEC
    HELTEC -->|"U.FL"| IPEX
    IPEX -->|"SMA"| BULK
    BULK -->|"SMA or N-type"| ANT

    subgraph ENCLOSURE["IP65 Enclosure"]
        HELTEC
        BATT
        IPEX
    end

    style SOLAR fill:#f9d71c,stroke:#b8a000,color:#333
    style ANT fill:#4a90d9,stroke:#2c5f8a,color:#fff
    style ENCLOSURE fill:#e8e8e8,stroke:#999,color:#333
    style HELTEC fill:#2d8659,stroke:#1a5c3a,color:#fff
    style BATT fill:#e06040,stroke:#a03020,color:#fff

Wiring Diagram

graph LR
    subgraph BOARD["Heltec V3.1 Board"]
        UFL["U.FL\nLoRa Port"]
        USBC["USB-C\nPort"]
        SH["SH1.25\nBatt Port"]
    end

    subgraph POWER["Power"]
        SOL["5V 6W\nSolar Panel\nUSB-A out"]
        LIPO["3.7V LiPo\nSH1.25-2P"]
    end

    subgraph RF["RF Chain"]
        PIG["IPEX→SMA\nPigtail 15cm"]
        BLK["SMA Bulkhead\nPanel Mount"]
        ANTENNA["433 MHz\nAntenna"]
    end

    SOL -->|"USB-A→USB-C\ncable 1m"| USBC
    LIPO -->|"SH1.25-2P\nRed=+ Black=-"| SH
    UFL -->|"IPEX click-on"| PIG
    PIG -->|"SMA-F"| BLK
    BLK -->|"SMA-M or\nN-type adapt."| ANTENNA

    style BOARD fill:#2d8659,stroke:#1a5c3a,color:#fff
    style POWER fill:#f9d71c,stroke:#b8a000,color:#333
    style RF fill:#4a90d9,stroke:#2c5f8a,color:#fff

Key notes:

The Heltec V3 has built-in LiPo charge management — no external charge controller needed.
USB-C input charges the battery AND powers the board simultaneously.
Use a USB-A to USB-C cable (USB-C to USB-C may cause charging issues on V3).

DIY 433 MHz Ground Plane Antenna

graph TD
    TIP["Tip"] --- VERT
    VERT["Vertical Element\n17.3 cm copper wire\nsoldered to center pin"] --- JOIN["Solder Joint\nat Connector"]
    JOIN --- CONN["SMA or N-type\nFemale Connector"]
    JOIN --- R1["Radial 1 — 17.3 cm\n45° below horizontal"]
    JOIN --- R2["Radial 2 — 17.3 cm\n45° below horizontal"]
    JOIN --- R3["Radial 3 — 17.3 cm\n45° below horizontal"]
    JOIN --- R4["Radial 4 — 17.3 cm\n45° below horizontal"]

    style TIP fill:#ff6b35,stroke:#c44d1a,color:#fff
    style VERT fill:#ff6b35,stroke:#c44d1a,color:#fff
    style JOIN fill:#888,stroke:#555,color:#fff
    style CONN fill:#555,stroke:#333,color:#fff
    style R1 fill:#4a90d9,stroke:#2c5f8a,color:#fff
    style R2 fill:#4a90d9,stroke:#2c5f8a,color:#fff
    style R3 fill:#4a90d9,stroke:#2c5f8a,color:#fff
    style R4 fill:#4a90d9,stroke:#2c5f8a,color:#fff

Parameter	Value
Vertical element	~17.3 cm (λ/4 at 433 MHz)
Radials	4 × ~17.3 cm, angled 45° down
Impedance	~50 Ω
Gain	~2.5–3 dBi
Target SWR	< 1.5:1
Material	Copper wire or brass rod, 1–2 mm

Tree Mounting Layout

graph TD
    ANT["433 MHz Antenna\n▲ vertical, above canopy"]
    MAST["PVC Pipe Mast\n1–2 m extension\nhose-clamped to tree"]
    CANOPY["─── Tree Canopy Line ───"]
    COAX["Coax Cable\nruns down trunk\n< 3 m ideal"]
    BOX["IP65 Enclosure\n+ Heltec V3\n+ Battery\nhose-clamped to trunk"]
    PANEL["Solar Panel\nmounted south-facing\n~45° tilt for LT latitude"]

    ANT --- MAST
    MAST --- CANOPY
    CANOPY --- COAX
    COAX --- BOX
    BOX --- PANEL

    style ANT fill:#4a90d9,stroke:#2c5f8a,color:#fff
    style MAST fill:#8B6914,stroke:#5a4510,color:#fff
    style CANOPY fill:#228B22,stroke:#145214,color:#fff
    style COAX fill:#888,stroke:#555,color:#fff
    style BOX fill:#e8e8e8,stroke:#999,color:#333
    style PANEL fill:#f9d71c,stroke:#b8a000,color:#333

Mounting priorities:

Antenna above canopy for line-of-sight
Enclosure below canopy for rain/wind protection
Solar panel south-facing, angled ~45°
Coax run as short as possible (every meter of RG-174 loses ~0.3 dB at 433 MHz)

Signal Path & Data Flow

flowchart LR
    A["Meshtastic\nClient Node"] -->|"LoRa 433 MHz\nLONG_SLOW"| B["Retranslator\nROUTER role"]
    B -->|"LoRa 433 MHz\nre-broadcast"| C["Meshtastic\nClient Node"]
    B -->|"LoRa 433 MHz\nre-broadcast"| D["Another\nRelay Node"]
    D -->|"LoRa 433 MHz"| E["ATAK Node\nvia Meshtastic\nplugin"]

    style B fill:#2d8659,stroke:#1a5c3a,color:#fff
    style A fill:#4a90d9,stroke:#2c5f8a,color:#fff
    style C fill:#4a90d9,stroke:#2c5f8a,color:#fff
    style D fill:#e06040,stroke:#a03020,color:#fff
    style E fill:#7b2d8b,stroke:#4e1a5a,color:#fff

The ROUTER role transparently relays all mesh traffic including ATAK CoT messages.

Parts List

Core Electronics

#	Part	Specification	EU Source	Est. Price
1	LoRa Board	Heltec WiFi LoRa 32 V3.1, 433 MHz, ESP32-S3 + SX1262	hamparts.shop (CZ)	~€22
2	Battery	3.7V 3000–6000 mAh LiPo, SH1.25-2P connector	AliExpress: search "3.7V 6000mAh lipo SH1.25"	~€10
3	Solar Panel	5V 6W USB monocrystalline, weatherproof	Amazon.de: search "6W 5V USB solar panel"	~€12
4	IPEX Pigtail	IPEX/U.FL to SMA female, 15 cm, RG178	PileupDX (SE)	~€10

Antenna (choose one)

#	Option	Specification	EU Source	Est. Price
A	DIY Ground Plane	1/4-wave, ~3 dBi, SMA/N-type	Copper wire + SMA connector	~€3
B	Ready-made GP	433 MHz ground plane with coax pigtail	hamparts.shop (CZ)	~€15
C	Fiberglass Collinear	433 MHz, 5 dBi, N-type, weatherproof	AliExpress: search "433MHz 5dBi fiberglass antenna N-type"	~€20

Enclosure & Mounting

#	Part	Specification	Source	Est. Price
5	Enclosure	IP65 ABS junction box, ~150×100×70 mm	Amazon.de: search "IP65 junction box 150x100x70"	~€8
6	Cable Glands	PG7 or PG9 nylon, IP68, pack of 10	Amazon.de: search "PG7 cable gland IP68"	~€5
7	SMA Bulkhead	SMA female bulkhead panel mount	Amazon.de / AliExpress	~€3
8	Self-amalgamating Tape	Silicone, for waterproofing antenna connector	Amazon.de	~€5
9	Silica Gel Packets	Desiccant, 5–10 g × 5 pcs	Amazon.de	~€3

Tree Mounting Hardware

#	Part	Specification	Source	Est. Price
10	Stainless Hose Clamps	Ø 80–120 mm, stainless steel, ×4	Hardware store / Amazon.de	~€8
11	PVC Pipe	25 mm diameter, 1–2 m, for antenna mast	Hardware store	~€3
12	UV Cable Ties	Black, UV-resistant, 300 mm, pack	Amazon.de	~€4
13	USB-A to USB-C Cable	1 m, for solar panel to board	Any	~€3

Alternative: Bender Case (replaces items 5, 6, 7)

#	Part	Specification	EU Source	Est. Price
—	Bender Case	3D-printed case with 18650 holder, SMA port, switch	PileupDX (SE)	~€15
—	18650 Battery	Samsung 35E or LG MJ1, 3500 mAh (genuine)	Nkon.nl (NL)	~€6

Cost Summary

Build Variant	Components	Estimated Total
Budget DIY	Heltec V3 + DIY antenna + LiPo + solar + generic enclosure	~€75
Mid-range	Heltec V3 + ready-made GP antenna + Bender case + 18650 + solar	~€90
Best range	Heltec V3 + fiberglass 5dBi collinear + Bender case + 18650 + solar	~€110

Firmware Configuration

After flashing Meshtastic via flasher.meshtastic.org:

# Region
meshtastic --set lora.region EU_433

# Role — ROUTER disables screen, minimizes power
meshtastic --set device.role ROUTER

# Modem — LONG_SLOW for maximum link budget
meshtastic --set lora.modem_preset LONG_SLOW

# Hop limit
meshtastic --set lora.hop_limit 3

# Fixed position (adjust to your location)
meshtastic --setlat 54.68 --setlon 25.28 --setalt 200
meshtastic --set position.fixed_position true

# Disable GPS (stationary node, saves power)
meshtastic --set position.gps_mode DISABLED

# Power saving
meshtastic --set power.is_power_saving true

Setup Flow

flowchart TD
    FLASH["Flash firmware\nflasher.meshtastic.org"] --> CONNECT["Connect via\nBluetooth or USB"]
    CONNECT --> REGION["Set region\nEU_433"]
    REGION --> ROLE["Set role\nROUTER"]
    ROLE --> MODEM["Set modem\nLONG_SLOW"]
    MODEM --> POS["Set fixed position\nLat/Lon/Alt"]
    POS --> GPS["Disable GPS"]
    GPS --> DEPLOY["Deploy to tree 🌲"]

    style FLASH fill:#4a90d9,stroke:#2c5f8a,color:#fff
    style DEPLOY fill:#2d8659,stroke:#1a5c3a,color:#fff

EU Seller Summary

Shop	Country	What to Buy	Link
hamparts.shop	Czech Republic	Heltec V3.1 433MHz, GP antenna	hamparts.shop
PileupDX.com	Sweden	Heltec V3 433MHz, Bender case, IPEX pigtail, antennas	pileupdx.com
Nkon.nl	Netherlands	Genuine 18650 cells (Samsung 35E, LG MJ1)	nkon.nl
Amazon.de	Germany	Enclosure, cable glands, solar panel, cables, tape	amazon.de
AliExpress	China → EU	Fiberglass antenna, LiPo battery, adapters	aliexpress.com

Important Notes

Battery connector: Heltec V3 uses SH1.25-2P (not PH2.0). Verify polarity before connecting.
Fake 18650 cells: Any 18650 claiming > 3600 mAh is counterfeit. Buy from Nkon.nl.
USB-C quirk: Use USB-A to USB-C cable — C-to-C may not charge properly on V3.
433 MHz in EU/Lithuania: License-free ISM band (433.05–434.79 MHz), 10 mW ERP or 25 mW with duty cycle limits. Meshtastic LONG_SLOW at 10 dBm is within spec.
ATAK compatibility: Relay transparently forwards all mesh traffic including CoT messages.

jarutis/mesh.md

Select an option

No results found