I have taken an interest in Meshtastic (An open source, off-grid, decentralized, mesh network built to run on affordable, low-power devices). For more information see: meshtastic.org/
I have a couple of device and have been playing around with swapping out antennas. One of the things to take into consideration is configuring the correct transmission power for the device, antenna and frequencies I am using. In this post I will provide a quick overview on how to calculate the Max TX Power in dBm. Jargon buster:
For this example I will use the New Zealand regulations for General User Radio Licence for Short Range Devices: gazette.govt.nz/notice/id/2022-go3100 EIRP It includes the following details: Low (MHz): 915.0000 High (MHz): 928.0000 Maximum Power dBW e.i.r.p.: 0.0 As I prefer to calculate using EIRP in dBm, the EIRP requires a simple conversion. dBm=dBW + 30 30dBm= 0.0dBw + 30 Total EIRP = 30 dBm GAIN To find the TX antenna gain it's easiest to get it from the antenna specification. For example I am using GIZONT 17cm antenna with a 10dBi gain. ATTENUATION As my devices have the antenna connected to the device motherboard I am going to assume the attenuation (Loss e.g. cables, connectors) to be effectively 0dB. To calculate the Max TX power: Max TX power = Total EIRP - TX antenna gain + Attenuation 20dBm = 30dBm - 10dBi - 0dB
0 Comments
Your comment will be posted after it is approved.
Leave a Reply. |
AuthorGeorge Timmermans, Research Toolmaker, Software Engineer and Tinkerer Archives
March 2024
Categories |