Meshtastic

Lora is impressive

I’m trying to do some mesh algorithm testing/tweaking which means I need to play with attenuation to get a multi-hop network.

I’ve used every pad in my radio kit, put the nodes at opposite ends of the house, used a directional antenna pointing away… and I still get -4.75dB SNR (26% signal).

That’s 140dB of hard attenuation! I guess the 154dB link budget for #LongSlow is a conservative number. Lora is quite impressive!



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I did a similar experiment with dummy loads as antennas, only to find out that the board leaks RF :wink:

Perhaps you could put the board in a metallic enclosure and see if the SNR changes.

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Hello colleagues. It is known from measurement practice that an open printed circuit board cannot be insulated by more than 80dB. Leakage of high-power RF currents to the case, the size of which is commensurate with or a multiple of the wavelength, is emitted very efficiently. For 900MHz, 1/4W is about 8cm, which is the length of the PCB. The area of the PCB emits very high RF power. To achieve attenuation 150 … 160dB (+ 20dB - (-140dB) = 160dB) Full blank RF shielding, including battery + external attenuators, will help you with this.

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I didn’t consider the PCB leaking RF because the lora module is shielded but I suppose the trace to the sma connector would act as an antenna for sure.

You could also just dial down the output power with the API:

meshtastic --ch-set tx_power 2

…to set the maximum transmit power to 2dBm, for example.

I ended up just using a dummy load. Knocked it down far enough to simulate a multi-hop mesh.