How to Measure and Determine the Maximum TX Power for RAK4631?

WisBlock
1

I am currently using the RAK4631 for a LoRaWAN project and have some questions regarding the TX Power settings. Based on the documentation, I understand that the TX Power is set using levels where:

TxPower 0 corresponds to the maximum EIRP settings,
TxPower 1 is EIRP - 2dB,
TxPower 2 is EIRP - 4dB, and so on.

Additionally, I am using ChirpStack v3, where the EIRP configuration can only be set via the device profile in ChirpStack.

  1. How can I measure the maximum TX Power achievable by the RAK4631 module?
  2. Is it possible to measure the TX Power without using a Spectrum Analyzer?
  3. How does the EIRP configuration work in ChirpStack? Does the gateway access ChirpStack as a broker and limit the maxEIRP based on that configuration? Is this the correct way it operates?

Thanks in advance for any guidance and suggestions!

2

(1) The max TX power of the LoRa transceiver chip is 22dbm, not sure what you want to measure here

(2) As far as I know, you need special equipment to measure the TX power. You can try to do some measurements with an SDR device, but that will be quite inaccurate.

For (1) and (2) the “real” TX power used is not only depending on the LoRa transceiver, but as well by the loss on the connection to the antenna and by the gain of the antenna. Without proper equipment I don’t think you can get any reliable measurements.

(3) You might get an answer to that in the Chirpstack forum

3

thank you for your answer. Yes, it is true that we only wanted to measure the maximum TX that the RAK4631 can do in dB, which at that time did not have a spectrum analyzer, and it is true that we measured it mathematically, since we didn’t use the spectrum analyzer. If it is listed in the datasheet it means we missed it when reading it, apologies.

4

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