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<p class="MsoNormal"><span lang="EN-US">HF noise measuring receiver project<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Chris G4HYG brings news of the internet linked HF noise measuring SDR receiver project he is working on.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">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.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">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.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">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.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">A prototype receiver has been running for over six weeks and its telemetry graphs can be viewed at this web page:
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">http://aprs.fi/telemetry/a/G4HYG-5<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">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.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Some interesting events can already be seen in the graphs over the last month.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">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.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">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.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">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.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">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.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">More information (slightly dated now) available here:
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">http://www.crosscountrywireless.net/noise_measurement_program.htm<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Information on the Noise Measuring Campaign by Chelmsford amateur Gwyn Williams G4FKH is at<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">http://g4fkh.co.uk/projects/noise-measuring-campaign/<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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