Before I go on to describe the project, here is a very interesting and popular article on HF background noise, by Vin Robinson – G4JTR, which appeared in the August 2012 RadCom. This article is copyright © of the Radio Society of Great Britain (RSGB) and was originally published in their magazine, RadCom, 08/2012. It is reproduced here with their kind permission. For more information about the RSGB please visit www.rsgb.org.
This campaign was announced in the July 2012 edition of RadCom. A copy of the page can be found here HF Measuring Campaign.
The subject can be emotive because everyone’s situation will be different. I.E. there seems to be a lot of problems associated with; Plasma TV’s, Power / Telephone lines, etc. My own situation is a lot simpler, whilst I live in a suburban area, all power and telephone lines are underground. Below is a link to a graph of my situation at the start of the campaign.
Noise Measurements – Clicking on the highlight to the left will bring up a chart showing my noise levels compared with those taken from ITU REC-372. The recommendation allows for a choice of receiver bandwidths so I chose 500Hz, a CW bandwidth, 2.1 or 2.4KHz could just as easily be utilized. The REC-372 measurements are taken from the accompanying computer program where the receiver bandwidth is requested. It can easily be seen that only on 1.8 and 14.0 MHz are my readings slightly above those for REC-372. It is only a matter of 2 or 3 dBm in each case. It can also be seen that I use the S-Meter reading that is nearest, therefore one S-point covers possibly 4 or 5 -dBm, depending upon whether the readings are higher or lower than the S-Point in question.
Those interested in this project have been sent an explanation of the campaign, to see it click here HF Noise Measuring Campaign Explanation.
As an addition to the original Campaign exercise a special purpose SDR Rx. (Sentinel) has been developed by Cross Country Wireless (CCW), along with a very small active aerial, ideally suited to this purpose. The CCW prototypes have been running for some time at the premises of Chris Moulding, G4HYG. I have been running my Sentinel along with my active aerial for a while now and am pleased with their performances, results from both stations can be seen graphically. It should be noted that the Sentinel can be used as a general coverage receiver for the frequencies between 2 and 15MHz, when not in use for Noise measuring.
The receiver monitors 5 discreet frequencies, 3.499, 5.258, 6.999, 10.090 and 13.399MHz. Each QRG is monitored in turn during a ten minute period, the median results being sent into the APRS system. Because of the reporting requirements, the controlling PC must have Internet access. Chris Moulding also points out on his web site that the developed program for this exercise will only run on older machines using either Windows XP, or Windows 2000. Thus older laptops can be put into useful service.
A good number of receivers would allow the Noise Measuring Campaign to make great strides as far as analyzing the impact upon HF of Plasma TV’s, PLA’s, RF emission from switch mode power supplies, etc.
It became apparent to me as soon as I received my Sentinel back in April 2013, that the Sentinel signal level output was in disagreement with my other radio equipment. I adjusted this straight away, but it took almost a year for me to realize that the Sentinel was suffering from something that a lot of other even top of the line rigs suffer from. That is; the S-meter / dBm readout is way off, in the case of the Sentinel way down. I have been in discussion with CCW for a good couple of months trying to get to the bottom of this and propose a solution. There is an obvious one, but I will wait to see what CCW say.
A new web site has been instigated to display recent results of the stations reporting into the APRS system. The URL is http://rsgbnoise.com, please note that this URL will change within a few months to the RSGB web site, this will be reported here. Comments and suggestions are very welcome.
Click July 2013 Results; to see recent interim results. The graphs are made up from data received from those participating in the campaign. Not too much can be inferred from these graphs but general trends will eventually be established, presently they show minor changes or changes in the local environment that can be explained.
Differences at receive sites include; (i) different Rx. Bandidths’, (ii) some of the Rx’s are calibrated but none are the same and (iii) some show S-Points whilst others show dBm. These differences are not important for this study, so continue as before.
July 2013 results show the following trends:-
G4FKH – Slightly Noisier, G3XGK – Mostly Quieter, M0LYD – Mostly Quieter, G4FPA – Slightly Noisier, M0RSJ – Mixed results and G4AHZ also with mixed results.
I have done some research into the display of information and found that the current format is superior. I tried Sparkline graphs along with other ideas, but they were found wanting. If anyone has a suggestion, I’d be happy to hear from them.
This page will be added to/updated as and when more information becomes available/relevant.
Any comments/suggestions e-mail – firstname.lastname@example.org