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

[Jim Brown]

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