[aprssig] HF noise measuring campaign reports via APRS

Chris Moulding chrism at crosscountrywireless.net
Fri Sep 14 14:41:54 EDT 2012

Recently Gwyn Williams, G4FKH has started a HF noise measuring campaign 
in the UK to investigate whether there is a national (or international) 
trend towards a higher or lower background noise level. Gwyn provides 
the HF predictions for the RSGB RadCom magazine and other national 
societies and has a long history of propagation studies so it's a 
serious amateur radio research project.

More information on the project here:


under "Projects/Noise Measuring Campaign".

At present he's asking radio amateurs to record S meter results on a 

The only problem is that the individual amateur's S meter readings are 
not calibrated so although they may show a general trend it wouldn't be 
enough to provide hard evidence to the regulator (OFCOM in the UK, FCC 
in the US) so they can take action.

I've suggested that I can provide SDR receivers with a separate 
calibration oscillator and software so that they can scan several HF 
frequencies and provide very accurate calibrated noise measurements so 
that they can be analysed for trends.

I'd like to add a feature in the SDR software to send the data by APRS 
status report via the APRS-IS. It would also allow every ham with access 
to APRS to view the noise data and run their own reports and analysis.

The data sent would be the RF frequency, peak noise level, the median of 
the noise sampled over a period of time and the minimum noise level.

At present I'm considering sending the data as a time stamped APRS 
status report. For example:


In this example the first frequency is 6.999 MHz, the peak noise is 
-100.1 dBm, the median is -110.1 dBm and the minimum is -120.1 dBm.

The second frequency is 10.100 MHz, peak noise -101.0 dBm, median -111.0 
dBm and minimum -121.0 dBm.
  The update rate would be say two status reports every 15 minutes so 
that the changes in HF noise over the day can be recorded.

With several stations recording data it would provide a very useful 
reference over APRS to HF band noise conditions as well as providing 
valuable long term data.

Does anyone foresee a problem with this?

If anyone can think of a better way to do it I'm open to ideas.


Chris, G4HYG

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