[RFI] What Possibly Is This RFI??

[K9MA]

On 10/1/2025 3:35 PM, Christopher Wawak wrote:
> Tune to an unused frequency in the AM band where you can hear the noise.
> Then, start walking around your property, neighborhood, etc. See where it
> gets louder or softer.
Alas, like many urban hams, I've had way too much experience tracking 
down RFI.

With all due respect, an AM radio is not likely to be helpful. The 
problematic interference may not be audible in the AM band, but many 
other sources probably will be. Even if you can hear the correct source, 
the AGC of the radio will make it very difficult to tell whether it is 
getting stronger or weaker.

For RFI other than power line noise, I've had the best results using a 
handheld HF receiver tuned to the same frequency as the station radio. 
If the interference is somewhat stable in frequency, that may allow you 
to make sure you're listening to the correct source. If there's any sort 
of modulation, that may be another way to identify the right source. A 
telescoping antenna is helpful: by shortening it until the RFI is right 
at the receiver noise floor, you can tell if you're getting closer.

For tracking power line noise, I've used a VHF tracking receiver. To 
identify the correct source, I have a licensed friend relay the AM audio 
from the station receiver on 2 meters, so I can hear it at the same time 
I'm listening to the tracking receiver. (Latency of a cell phone will 
render it useless.) There is almost always an audible pattern to line 
noise, so I can tell when they match. That's very important; otherwise, 
you will waste a lot of time tracking down the wrong noise sources, of 
which there will be many.

73,
Scott K9MA

-- 
Scott  K9MA

k9ma at sdellington.us