GregS wrote:
I have been looking at these. I saw one once and it
seemed to respond well to noise in a room, such as from
lighting. I have been making a noise detector for a while, which
has selectable types of noise, electrostatic, magnetic, light, and
vibration. I really need to just get one of these and experiment, but
the Progressive (now Tempo or Textron or Greenlee ??)
probe say inductive while I really thinks its a basic electrostatic
probe. I'm thinking of modifying it since its so inexpensive.
I don't know if it has any filtering of frequencies in the circuit.
Anyone know about these ?

greg

I've been using these for years, and they are definitely inductive. The
reason you may think they are electrostatic is the scratchy noise that
comes from moving in and out of minor magnetic fields that surround any
metallic circuit.

If you are really looking into noise detection, try one of these (the
Model 245 at the bottom of the page)
http://www.radarengineers.com/rfitvi.htm