[RFI] RFI at W9RE on 160 meters tracked down to transmission line 2.7 miles away

[Dave (NK7Z)]

Here are two links related to this:

https://www.nk7z.net/sdr-rfi-survey-p1/

https://www.nk7z.net/rfi-site-survey-part-ii-interpretation/


73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources

Random Quote of the day:
I don't like country music, but I don't mean to denigrate those who do. 
And for the people who like country music, denigrate means 'put down'.
Bob Newhart

On 2/10/26 11:15, Jim Brown wrote:
> On 2/9/2026 2:31 PM, Don Kirk wrote:
>> On the first day I had limited time and Mike and I tracked the RFI 
>> down to
>> an area 2.6 miles away from Mike's house where we could also hear it 
>> on VHF
>> but we had a hard time believing this was correct as this was almost a 
>> mile
>> more than anything I had previously tracked down.
> 
> I have preached for years to understand the difference between impulse 
> noise and electronically generated noise, to identify what you have 
> using spectrum displays, and to use the appropriate method for each. 
> Electronically generated noise is seen as vertical lines on a waterfall, 
> impulse noise is seen as horizontal lines. Lightning and arcing on power 
> lines are the most common impulse noise, but there are other possible 
> sources, like failing doorbell transformers and electric fences that arc 
> to vegetation.
> 
> Virtually all noise generated by power systems is impulse noise, and the 
> best way to track it, by far, is at the highest frequency where you can 
> listen. In the case you're describing, I would be driving around with a 
> radio with an AM detector hooked up to a VHF/UHF whip listening around 
> 160 MHz until it got really loud, then moving higher in frequency as I 
> get closer. I'd also try DFing it with a UHF yagi if I could hear it 
> with the whip. When I get close, I get out of the car with the talkie. 
> Held at my chest, it's a half-space antenna, with or without a duck 
> attached. When I get really close, I remove the duck. I learned this 
> technique from others in my Chicago ham club during fox hunts, and won 
> one using it. :)
> 
> My Kenwood mobile FM rig and Kenwood talkie have wideband RX to above 
> 500 MHz with AM and SSB detectors.
> 
> By contrast, electronically generated noise is rarely that broadband, 
> must be chased on frequencies where we hear it, AND the spectral and 24 
> hour waterfall analysis developed by NK7Z is extremely useful for two 
> reasons. First, it lets us distinguish between multiple sources, so that 
> our DFing doesn't get confused. Second, it tells is time of day that 
> these sources are present, telling us when to chase them AND giving 
> clues about what those sources might be (for example, street lights, 
> industrial machines, power control devices). Search on his call to find 
> his work. I've used his techniques, which are detailed for an SDR RX 
> that HRO sells for about $140, with free software for Windows OS.
> 
> 73, Jim K9YC
> 
> 
> 
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