[RFI] Mystery Noise (Aren't they all)

[Jim Brown]

On 1/28/2024 7:50 PM, Wes Stewart via RFI wrote:
> Any other suggestions?

Hi Wes,

Lots here.

http://k9yc.com/KillingReceiveNoise.pdf

Broadband RF spectrum analysis, including a long time waterfall, in the 
range where you're hearing it helps us figure out the nature of what 
we're looking for. That is, is it arcing or electronic stuff.

We have long known the characteristics of arcing, and to chase it at the 
highest frequency where we hear it. With electronically generated stuff, 
we must chase it where we hear it.

NK7Z developed this excellent methodology using a low cost SDR RX ($120 
at HRO). Software to run it is free. Dave provides lots of detailed 
setup instructions.

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

Armed with what we learn from both this collection of information, we 
use traditional DFing techniques. It provides time of day info, allows 
us to distinguish between multiple sources by how they drift in 
frequency. Time tells us when to look, identifying the different sources 
can prevent us from wild goose chases, or even let us chase one, then 
the other.

My app note lists several battery-operated tools I've used. They include 
a pretty good Tecsun AM/FM/shortwave RX that sells for about $40. A very 
broadcast engineer pointed me to it years ago.

If it's arcing, I have the broadband RX in both my mobile FM rig and my 
talkie programmed with frequencies in the VHF and UHF range, starting at 
160 MHz, and four more up to about 550 MHz where the general coverage 
stops. The antenna is a vertical whip, either a mag mount or a trunk lip 
mount.

Since I'm chasing arcing, I drive around tuned to 160 MHz, and as the 
noise gets louder, I switch higher in frequency. When it gets really 
loud, I get out of the car with the talkie at that highest frequency and 
walk around. One trick I learned at one of the Fox Hunts of the 
Chicago-area club of which I was a member was to hold the talkie right 
against my chest, giving it a half-space pattern.

Don't limit yourself to tools you own -- check with members of local 
clubs to borrow stuff.

73, Jim K9YC