ARLA/CLUSTER: Projecto para medir o ruido em HF

[João Gonçalves Costa]

HF noise measuring receiver project

Chris G4HYG brings news of the internet linked HF noise measuring SDR receiver project he is working on.

The project I'm working on is a HF noise measuring SDR receiver (or transceiver) and a SDR program to accurately measure HF noise levels and send reports to the APRS internet system so that the data can be viewed and stored for later analysis.

The receiver monitors five channels with a 500 Hz receiver bandwidth. There are three fixed channels 6.990, 10.090 and 13.4 MHz and two user defined channels. For testing I'm monitoring 10.1 MHz (DDK-9 10 kW weather RTTY from Hamberg 500 miles due east) and 8.0396 MHz (GYA weather fax) with the user-defined channels.

Each RF channel is monitored for 2 minutes. 500 samples of the RF level are taken. The median level is calculated and every 10 minutes the data is sent as a telemetry packet to the APRS internet system. A message with peak, median and minimum levels is also sent to Gwyn Williams, G4FKH for his research project on HF noise.

A prototype receiver has been running for over six weeks and its telemetry graphs can be viewed at this web page:
http://aprs.fi/telemetry/a/G4HYG-5

The page starts up with graphs of the last 48 hours but it's possible to select the last day, week, month and year as well.

Some interesting events can already be seen in the graphs over the last month.

On November 14 after the CME from the Sun no signal was heard from DDK-9 all day due to a radio fade out. Typically it's 40 dB above the noise.

200m from my antenna is a school. From October 28 when school started after half term my noise level rose by 5 dB on 30m and 3 dB on 20m.

The intention is in the new year to start producing the SDR receiver with a CW transmitter with a iambic memory keyer added to the program.

The idea is to have a unit that radio amateurs can use for normal ham use and then leave running in noise measurement mode at other times.

More information (slightly dated now) available here:
http://www.crosscountrywireless.net/noise_measurement_program.htm

Information on the Noise Measuring Campaign by Chelmsford amateur Gwyn Williams G4FKH is at
http://g4fkh.co.uk/projects/noise-measuring-campaign/

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