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This site is designed for mmWave operators and shows the expected atmospheric attenuation (db/100km) on the amateur allocations from 24GHz upwards.

Note: These figures are in addition to the normal free space path loss which you will need to determine for the path you are using.
The atmospheric loss figures shown here are directly proportional to the distance. i.e. half the distance, half the loss.

The attenuation figures are calculated using the method described in Annex 1 of 'Recommendation ITU-R P676-11 (09/2016) Attenuation by atmospheric gases'.
You can get a copy here if you're interested.

This site obtains weather observations from the Bureau of Meteorology web site. I use a Windows service to read the weather observation pages for each state
(e.g. and then pick the data out of the html. This is then written to a SQL Server database which is used
as the data source for this web site.

The Bureau provides the following data:
Not all stations provide barometric pressure data. In these cases, a standard pressure of 1013.1 is used for the loss calculations (shown in italics on the web page).

The Absolute Humidity is calculated from the temperature and relative humidity.
See here for details.

The exact frequencies used to calculate each column are:
 24GHz = 24.048GHz
 47GHz = 47.048GHz
 76GHz = 76.032GHz
122GHz = 122.3GHz
134GHz = 134.0GHz
241GHz = 241.0GHz

The Absolute Humidity data is highlighted red if the value is above 7.5 g/m3 and green if below 3.5 g/m3

Last Refresh: 14-Jun-2024 23:54:59

Bureau of Meteorology