One very useful tool is a software-defined receiver and the associated
spectrum display software. for example, I was troubled with an audible
increase in the noise floor at the bottom end of 160. The spectrum
scope showed a pattern with regular, broad peaks every 70 KHz or so.
Armed with that, I discovered a noisy computer power supply, added a
Corcom filter to the AC, and voila!
Re Kelly's problem, I've found that one of the best tactics with the
neighbors is to suggest that what is causing the interference could be a
fire hazard. This has the advantage of even being true in many cases,
such as an arc in house wiring due to a loose connection. Paul's right,
of course - being able to prove the source of the interference is
essential. I have taken my 2-meter AM RX and 2-element Moxon around to
people's houses, and demonstrated that when I point it their way, the
noise goes off-scale. I've also had fairly good luck, after
demonstrating this, in getting people to let me come inside to try to
localize the source. But dodgy renter neighbors can be a different problem.
73, Pete N4ZR
The World Contest Station Database, updated daily at www.conteststations.com
The Reverse Beacon Network at http://reversebeacon.net, blog at
spots at telnet.reversebeacon.net, port 7000
On 8/16/2010 7:06 AM, Paul Christensen wrote:
> You'll need to start documenting the interference. To the best of your
> ability and time, keep a log of the times the interference starts and
> stops -- even if its days in between. As has been suggested here on
> numerous occasions, first ensure that the interference is not coming from
> your own property. That involves turning off all panel breakers and
> disconnecting battery-backed systems (e.g., security alarms).
> It's unreasonable for the neighbors to be turning on/off power without
> evidence. You need to secure some minimal evidence before making contact
> with them. If you don't, you're only a boy crying "wolf!" at best. At
> worst, you've just become the new neighborhood crackpot.
> The mind begins to conjure all kinds of things when the interference is
> really bad. "I need to move," "questionable renters," and "super powerful
> computers" mean nothing when you really need to flesh-out the root cause of
> Today, we're confronted with more sources of interference than ever before.
> But fortunately we have some tools that were not available until recently.
> It may take you some time, but if you want to get really proficient at noise
> source detection, you're going to have to become knowledgeable with noise
> patterns and select the right equipment for detection.
> Before contacting neighbors, utility company or the FCC, you really need to
> have your facts straight. Simply turning your beam in the direction of the
> perceived noise source isn't nearly enough. You've got to localize it
> through triangulation.
> I have two systems here:
> (1) The first is a hand-held 3-element 2m Yagi and a 2m HT capable of AM
> mode. This system is primarily used for broadbanded power line noise;
> (2) The second system has been seeing much more use here in the past year,
> primarily due to the increased proliferation of switch-mode appliances. It
> consists of an Elecraft K3, SDR-IQ with SpectraPlus software, netbook PC,
> Palstar active rotatable loop antenna, and a small 12V gel-cell battery. I
> purchased a mid-size Pelican case to allow me to quickly set-up and break
> down the equipment as I roam the neighborhood. I generally do not need to
> access the neighbor's property. Most of my measurements are taken at the
> street or from within my property.
> After some time spent with switch-mode noise sources, I can now localize a
> noise source in about 30 minutes to nearly pin-point accuracy. However,
> some noise begins in a room of the home, and the home wiring propagates the
> noise to make it appear as if its coming from a different part of the house.
> That's one reason why it's so important to move around and take quality
> measurements. My system is self-documenting. I take PC screen captures of
> SpectraPlus showing noise levels all pointing to a single location. That
> becomes my evidence for presentation to a neighbor, or if necessary to the
> FCC. When you've got that kind of powerful data, the FCC is really on your
> side. But you cannot go to the FCC and talk in terms of "questionable
> neighbors," and "super powerful computers."
> It may seem like this is all going over-the-top in equipment and procedure,
> but if we want to enjoy the hobby without running a noise blanker all the
> time, we all need to become proficient in recognizing noise source patterns
> and know how and what type of equipment is needed to detect the problem with
> a high degree of accuracy.
> Paul, W9AC
> ---- Original Message -----
> From: "Kelly Johnson"<email@example.com>
> To: "RFI List"<firstname.lastname@example.org>;<email@example.com>
> Sent: Sunday, August 15, 2010 10:19 PM
> Subject: [RFI] Am I hosed? RFI problems
>> It took me two weeks, but I'm now about 99% certain that I found the
>> source of my horrible RFI problem. It's a house about 100 yards from
>> me. A group of questionable renters just moved into that house a few
>> weeks ago. The noise is worse than anything I have ever heard. It's
>> S9/S9+ on 40m through 10m; dropping down to S7 or so on 6m (all while
>> I beam that direction, which is unfortunately the direction I must
>> beam for the East Coast from here in CA). I can null it out if I beam
>> perpendicular to that direction, but unfortunately, there aren't that
>> many stations of interest directly north or south of me :-(
>> When I told the renter today that I have heard the noise start at 8am
>> the last 2 days, his first response was: "there's a guy here that has
>> a very, powerful computer that he turns on at 8am". He asked the guy
>> to turn it off to see if it was the source and the guy clamed to have
>> done it, but I don't believe he did. I think he was just trying to
>> get rid of me. The noise was still there. When I asked the guy if he
>> would be willing to shut everything off to see if it went away he said
>> no. I don't know what to do now. My HF station is nearly worthless
>> at this point with S9+ noise. I can't hear much of anything above the
>> hash. My S meter read S0 last night at 10:30pm and still S0 this
>> morning from 6am until 8am. I was sitting in front of the radio at
>> 8am when the noise came on. The S meter instantly jumped from S0 to
>> about S7. It slowly got worse until it peaked at S8 on CW in a CW
>> 250HZ bandwidth and S9+ in a 2KHz bandwidth on SSB.
>> Any advice (other than move, wait for these guys to move, or something
>> RFI mailing list
> RFI mailing list
RFI mailing list