RFI Hunting

Today, we as HAM radio operators, are constantly fighting against man-made noise. We could say that RFI “kills” (y)our hobby and also takes the fun out of it when we have a QSO on a particular band or frequency where QRM is more common than rare. Because of this so-called Man Made Noise I developed a new sport, so-called RFI Hunting šŸ™‚ . Many people during this pandemic go for a walk with their dog, go bird watching or do something else … But when I leave home, I do not take my dog or binoculars outside, I take my RFI Hunting Tools. In this case the IC-705 with an active magnetic loop MLA-30 + powered by a 4000 mAh PowerbankĀ  and an RF Explorer spectrum analyzer.

Pic 1: MLA-30+ Active Magnetic loop, IC-705 and Carry bag

During my frequent walks through my neighbourhood, I am trying to find and exactly pin point the location where the RFI is coming from. Last year (2020) I managed to find 4 different RFI sources and made some new friends in the process. Think of LED garden lighting, a Micro-controlled Powerbox and more. With all the neighbours where I found the RFI source, I had a nice friendly chat and explained what RFI is, what the problems are, what causes the RFI, etc … ! I guess we as HAMS all have similar experiences ...

The last Man Made Noise I encountered was with my new neighbours who moved in at the beginning of this year(2021), because immediately after they moved in, I start having problems at 40 meters where I couldn’t hear anything due to the high noiselevel caused by RFI (see pic 2)

Pic 2: Mand made Noise: RFI of 5/9+ 24/7 across the whole 40mtr bandĀ 

After using my RFI Hunting tools, I manage to find the culprit. Apparently my new neighbours weren’t using the Cable provider for their TV, IT and Phone like my former neighbours had, but instead were using theĀ  National Telecom provider. This meant that their modem went through the Wall socket Telecom infrastructure(ISRA) instead of the Cable Antenna infrastructure. At that specific ISRA I measured – 33dbm (5/9 + 40db) so the interference had to come from there. Just before Christmas I was lucky enough to come in contact with “THE” Techical Guru of that specific National Telecom provider about another matter. So after I found this specific RFI, I phoned him and kindly asked if he could see anything on my neighbor’s infrastructure as these telecom and cable providers nowadays can track all of our interaction remotely through their infrastructure network. About 1 hour later he called me back and told me he already installed some digital notches on my neighbour’s profile and Eureka, the problem was gone (see pic 3)

Pic 3: You can clearly see the 40mtr band being Notch out as the Notch start at 6.926 – 7.274 mHz

But after this “Eureka” moment the story wasn’t over as I still had RFI outside the 40 mtr HAM band which meant I couldn’t listen to the Broadcast band because of the High Noise level 24/7. By looking a bit further into my neighbour’s Infrastructure, the Technical Guru saw that their specifc inhouse infrastructure had a Bridgestep inline. This parallel line may have existed in the past as a 2nd telephone line elsewhere in the house but was no longer in use. So that meant that the National Telecom provider would make an appointment to remove the Bridgestep. A few days later when the field engineerĀ  opened the ISRA, they found a “MacGyver” kind of solution of a few crossed wires. (see pic 4) By disconnecting the Bridgestep and connecting the ISRA wall socket as it should, all was fine and the RFI was completly gone.

Pic 4 Bridgestep

After this strange ordeal and fortunately knowing the right people within the National Telcom provider, I was lucky enough to solve this problem. So another RFI Hunt was found and resolved. Currently we already are working on the next RFI issue within my neighboruhood ….

RFI Hunting is a never ending story but it is worth to take this road as in the process you will meet new interesting people and at the same time educate people on RFI & the interesting world of HAM Radio.

If you want to know more of my prevous experiences please do not hesitate to drop me an email at roma-dx@ziggo.nlĀ or just use the CONTACT form on this webpage

73 Roberto PB5X