[RFI] Fw: RFI Signature

[Jim Brown]

The RFI signatures that are most useful in providing clues about the 
nature of the source are wide waterfalls of the IF or RF. NOT audio -- 
almost all noise sources are somehow related to mains power.

Noise that show up as vertical humps of noise spaced from each other in 
the range of 30 - 60 kHz, and that may drift around a bit are some sort 
of power-handling electronics, like SMPS (wall warts, line lumps, 
chargers, even built into products like TVs, stereo gear) and 
controllers for variable-speed drive motors.

Narrow straight vertical lines are from devices like microprocessors.

Horizontal lines are impulse noise, generated by lightning and arcing at 
various forms of hardware on power lines.

About ten years ago, I published an on-line tutorial showing typical 
waterfalls, and NK7Z responded with a lot of excellent work using an 
inexpensive SDR receiver. The first link is to a piece that ran in NCJ, 
the second to slides for a talk I did at Pacificon and Visalia, and to 
several clubs. The talk was later, so includes more graphics.

http://k9yc.com/KillingReceiveNoise.pdf
http://k9yc.com/KillingRXNoiseVisalia.pdf

73, Jim K9YC

> I am working on a RFI case that we believe is coming from a nearby home.
> The owner is a little cooperative, but is not interested in doing a ckt
> breaker test.  The noise exhibits some interesting characteristics that may
> help us in suggesting he unplug a device.  Perhaps someone has seen this
> before.
>