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RAK 1W LoRa Booster Build

The RAK3401 is a 1-watt LoRa booster kit designed for MeshCore and Meshtastic nodes. It pairs with a standard RAK WisBlock base board and adds a dedicated PA stage that pushes output to the legal limit - a meaningful jump over the ~100mW you get from a stock WisBlock radio module.

The Board

The RAK3401 kit consists of a 1W PA module that mounts on top of a compatible RAK WisBlock base board. It replaces the standard LoRa module slot and handles the RF amplification internally, so no external amplifier or additional wiring is required.

~$35–45

RAK Store

Powering the 1W Board

The higher output power means higher current draw compared to a stock WisBlock - so how you power the board matters. The tested configurations are:

Mode Description
Battery only LiPo battery connected to the RAK battery input - useful for testing, not a typical deployment
USB only Powered via USB-C, no battery
USB + Battery Both connected simultaneously - a common real-world setup
External 5V External regulated 5V supply via the WisBlock 5V input

The PA's current demand during transmit is the key variable - the power source needs to be able to supply it fast enough to sustain full output.

USB-only is the exception

Testing conducted by ThatGuy in the MeshCore Discord showed that USB alone is the one mode that falls short. An external 5V supply and USB combined with a battery both produce equivalent full output. The battery-only test - while not a typical deployment - confirms it's the battery that makes the difference: USB power by itself cannot source current quickly enough to maintain the PA at full power during transmit.

Spectrum analyzer comparison - Batt Only vs Ext 5W vs USB+Batt vs USB Only

The measurements were taken through a 40 dB attenuator. The top capture is Batt Only reading -10.1 dBm at the analyzer - correcting for the attenuator puts true output right at 30 dBm (1W). The bottom row shows External 5V, USB + Battery, and USB Only - the first two match the battery-only result, while USB alone trails behind.

Key takeaway

Battery alone, external 5V, and USB + battery all achieve full 1W output. USB alone does not - it can't source current fast enough to sustain the PA at full power. For any deployment where you're plugging in via USB without a battery, expect reduced output.

This also means a standard RAK WisBlock solar + battery setup is fully suitable for a 1W deployment. The solar panel charges the battery through the WisBlock's solar input; the battery is what actually drives the PA, so full output is maintained regardless of whether the panel is actively charging.

Deployment Notes

  • Use a quality LiPo with adequate C-rating - the PA draws significantly more current during transmit than a stock radio. A cheap or undersized battery may sag under load.
  • A solar charging setup works well with this board. The RAK WisBlock solar input handles the charging; the battery buffers transmit current spikes the same as any other deployment.
  • The higher output power increases heat. Avoid sealing the board in a completely unvented enclosure without accounting for thermal management on long-running repeater nodes.
  • Antenna quality matters more at higher power. A poor antenna or bad SMA connection wastes the extra power as heat in the connector.

Next steps