MEWS: Marine Electronics Wiki

This page is read only. You can view the source, but not change it. Ask your administrator if you think this is wrong.

====== Notes on LoRa Propogation / Radio Tests ======

===== Hacklab =====

==== 31 July 2024 ====

Testing a path to the installation on Summerhall B-Block roof to nearby in Edinburgh. RSSI of -96dB on both ends. SNR on roof -16.75, -18.75, SNR other end +2.5dB. It seems the roof is very noisy and severely limiting that location. I don't know if it is picking up more noise from other radios on the roof, it is sited well for interference from more distance ones, or it is other EMI. Maybe something in the box itself.

The roof also has a LoRaWAN TTN station and a Helium node within a few meters.

===== Small aerials in city =====

During a test with Heltec Wireless Tracker, I received on the edge of the usable range:
RSSI: -123dBm, SNR:-17.3dB. This was heard from the Heltec v3 a few large flat blocks down the road.

SNR(dB) = sig(dB) - noise(dB)
-noise = SNR - sig
noise = sig - SNR
noise = -123dBm + 17.3dB = -105.7dBm

Meshtastic was on the default LongFast setting, which uses:

<del>TX power 27dBm (500mW)</del> 22dBm. It was set to 27dBm but max of radio is 22dBm. SF 11.

SF 11 requires -17.5dB SNR, so SNR was just acceptable by spec.

In a later test, with VeryLongSlow, lowest RSSI seen with connection was -124dB and -6.0dB SNR, so not better.