I have RFI: Series
RFI Site survey – Part II, interpretation
This is part II in a series of articles which will cover how I interpret and use SDR captured spectrograms as they relate to my RFI mitigation efforts. See Part I, Using a SDR as a Site Survey Tool for how I setup and use the SDRPlay RSP1 as my SDR of choice, while using HDSDR as the radio control program. The concept was to view my RFI environment as a whole, not in realtime, but across long periods of time, and very wide frequency spans. Continue reading
RFI Snapshots
Clicking on any of the images on the RFI category page will take you to yet another page, which contains any number of RFI signatures. This may be helpful in identifying a source of RFI. While it is not a a RFI fingerprint, it is an indication of what may be causing your RFI. Continue reading
Using a SDR as a RFI site survey tool
Over the past several years it seems I have done nothing but hunt RFI sources. This process reminds me much of the old childs game called “Whac-A-Mole”. So the use of a SDR came to mind… This is how I set up an SDR site survey tool. Continue reading
I have RFI, now what– Locating it
This allows me to verify I am working with the same RFI source. I record the audio from the FT-900, and then I can play it back into Spectrum labs, and see if it matches the RFI I am hearing at home. Once I have a match, I know without a doubt I have the same source. I then look at the map, and it becomes pretty obvious where the RFI is most of the time. I next start running the frequency up as high as possible and still hear the RFI. I then grab a Google Map of a smaller area, around where the signal is strongest, and do the drive around again. I repeat this process moving ever higher in frequency. Continue reading
I have RFI, now what– House Cleaning
I then brought up each circuit one at a time… Remember I had all the major appliances unplugged, so this test is looking for the various vampire devices that suck electricity all the time, pretty much anything with a wall wart on it. First I brought up the kitchen. That caused no issues, so I started turning on lights, and plugging things back in. The first source of RFI I found was a set of LED lights I got from Walmart. They are the ones that look like a 100W light, and put out about as much light as a 100 watt light. I heard nothing from them on 80, 40, 30, or 20. However on all bands above 20, they put out a horrific spray of RFI. Had I not checked all bands between testing I would have missed this. OK I noted this in my log book, and put a note there to change them out later. I turned them back off, and plugged in the refrigerator, I got a bit of RFI, so I added a few 31 mix ferrites to the power cord, and that RFI did not return. Next the Microwave got plugged back in, again, a small amount of RFI, and again a ferrite or two took care of this. There were no wall warts in the kitchen, so that pretty well took care of things for the kitchen. Continue reading
I have RFI, now what– Quantification
Over the past few years my RFI problem has been getting worse and worse. 40 Meters was unusable due to QRM last year, I am only now beginning to be able to use 40 meters again. Other hams in the area, (1/2 mile away), closer to the source of the RFI have lost the entire HF spectrum. See the movie above. Hit play, and all looks well until about 22:30 GMT, which is about 3:30 PM in my local time zone. As you can see, the RFI goes off scale at that time. The S Meter reading for that signal is around 10 db over S9. It is also affecting three other hams in the area. One poor fellow is so close to it that all ham bands are wiped out, 160 Meters through 10 meters are unusable during this time frame. There is another ham located about 1/4 mile from the source, he has just moved in, and was unaware why his use of 40 meters was precluded due to RFI. So there are folks who have it worse than me in this! Note this is an older recording, currently the start time for the RFI has changed to 01:36, or 7:36 PM local time. All in all there are 4 and possible 5 hams affected by what is a single source, over one or two square miles, all from a single source. We have the general area pinned down, and this summer, (2014), we are going to locate the house, and either contact the owner, or request FCC assistance. Continue reading
