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 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
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
This document was prepared because of the widespread lack of valid technical
information about site performance at all levels of receiving-site operation. For example,
the information about grounds and grounding available to site personnel was especially
confusing and often downright incorrect.
Complex analytical procedures have been avoided to make the text as readable as
possible, but it is assumed the serious reader will have a good knowledge of the physical
laws related to basic electricity. This includes an understanding of the flow of electricity
in complex circuits, some understanding of the impact of reactive impedance on the flow
of electricity, a basic knowledge of the properties of electric and magnetic fields
surrounding conductors carrying electric current at both low and high frequencies, and
the inductive and capacitive coupling of current and voltage from one conductor to
The basic principles of noise and interference mitigation techniques are also included.
The integrated use of electromagnetic barriers, filters and grounds to confine
electromagnetic noise to its source device is described. This is an effective technique to
mitigate identified sources. Practical mitigation examples are described as well as
ineffective solutions. Continue reading
S-Meter Lite will graph S-Meter readings in real time, save spreadsheet ready files over very long time frames of your S meter values, assist in generating a pattern for your beam antenna, show RF levels in S units or in dB, and show signal level differences in dB between one signal and another on the same graph. Continue reading
Overall it was useful to me in locating a few sources of RFI, you point it in the general direction of a noise source, and wave it around until you get a peak in the meter. Once you have that, you walk towards the source, waving the antenna around, following the peaks.
The device is reasonably well constructed, MFJ quality control seems to be good, as the unit I got has no defects in it. It came boxed nicely, and was simple to construct. There were a few items to note… Continue reading
When an arc happens on a power pole, it, in some cases generates not only RF noise but noise in the ultrasonic spectrum as well. Again the ARRL has a very nice article on this subject here. So this kit is designed to listen for that ultrasonic noise, using a fairly sophisticated DSP audio receiver. In fact, this device has a lot of similarities to to a SDR radio, again, the ARRL has a short article on SDR here. Continue reading