[RFI] Tracing wires.

[Cortland Richmond]

On 1/20/2016 12:41 AM, KD7JYK DM09 wrote:
> In the early 90's I bought a wire tracer "pen".  It ran on a single AAA
> battery, looked like a rectangular laser pointer, had a metal tip.  I bought
> mine at All Electronics for a few bucks, Radio Shack had them as well for
> more.
>
> I found I could sweep a wall and locate a "hot" wire behind sheetrock,
> plaster, et cetera.  I would press the button, then "sweep" the tip across a
> wall and watch for a red LED on it to illuminate.  When it did, I could
> sweep more slowly to narrow down the inch or so it would light, then make a

Here's a variation on that you can use with an all-band HT or handheld  
receiver with a coaxial connector, Yaesu VR-500, Alinco DJ-X10 or 2000,  
AOR 8200 etc.

You can use a current clamp 
[http://www.interferencetechnology.com/wp-content/uploads/2012/04/Wyatt_NA_DDG12.pdffigure 
3 ] to couple a SG to an equipment cord plugged into the outlet, or just 
plug in a REALLY noisy battery charger or SMPS PS, maybe for an old 
laptop computer.

Make a small loop antenna  (something like the bottom one at 
http://m.eet.com/media/1161339/fig4_loop_probes.png ). Plug it into the 
receiver and tune for SG (or the strongest noise) frequency while 
holding the antenna it as close as possible (and safe!) to the wiring 
run, one edge on or near the wires and the loop in the same plane as the 
wiring; you will be following the non-radiating inductive field, which 
falls off as the inverse cube of distance from the conductor.

I've used smaller loops to follow clock traces on a PW board, once even 
through a poorly coatednickel-paint-shielded plastic enclosure.



Cortland Richmond
KA5S
(EMC since '83)