[RFI] Quidance on finding noise?

[donovanf at starpower.net]

Hi Kenny, 


The RFI you describe certainly appears to be triggered by sunset, 
either a streetlight or one or more outdoor lights in a residence. 
Night time only RFI is extremely rare on power lines. 


You've got the right idea about how to track 160 meter RFI. A loop 
antenna will provide excellent directivity and will immensely valuable. 
As you get closer to the RFI source you should be able to go up in 
frequency, ultimately to perhaps 450 MHz. But not always... 


Some RFI sources do not produce much energy at VHF and above. 
Two of my most eggregious RFI sources were exactly that way. One 
was an electric fence charger that failed continuously on (no pulsing) 
and produced RFI only below about 2 MHz. The other was a 
Highway Advisory Radio Station with a failed synthesizer that produced 
S9+ broadband RFI all over the 160 meter band b ut nothing above 2 MHz. 


Good luck with the hunt! 


73 
Frank 
W3LPL 





----- Original Message -----

From: "Kenny Silverman" <kenny.k2kw at gmail.com> 
To: rfi at contesting.com 
Sent: Wednesday, January 8, 2020 4:55:11 AM 
Subject: [RFI] Quidance on finding noise? 

Hi and thanks in advance! 

We’ve been trying to track down some noise at a friends house but no luck so far and I was hoping for some tips on finding it. The buzz comes on at sundown and turns off at sunrise. It’s bad on 160 but it can be heard Lightly on 80 and 40. The noise is constant and does not cycle (at least for the 90 minutes I was listening to it tonight). The worst direction is on the East beverage on 160. On 80m it seemed like the worst was to the NW... it could be 2 sources but the noise appears to come on at the same time in all directions, not a staggered turn on/off. Could be a single source but poor F/B on the beverages. The Listening to the ARRL RFI files it sounds like power line noise or street lamps ( but without the cycling). Over the 90 minutes tonight there were almost no variations (except for an occasional change in pitch). 

We've DF’d on a portable AM radio, 2m and ultrasonic device. AM identified some noisy poles but we’re not convinced these are the main offenders. Not much luck with VHF or ultrasonic. Our next plan is to use a KX3 on 160m and a decent RX loop to direction find and triangulate. 

I suspect we’re not looking out far enough... suggestions on how far away we should be looking? And how close do we need to be to hear it on VHF? 

Besides power lines and street lamps, other thoughts on possible offenders? Most of the area is residential with street lamps on most streets. 

Regards , Kenny K2KW 
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