Sniffer Probe

[Mikebits]

I want to build the sniffer probe in the image below. Problem is that the drawing is not quite clear to me on how to construct the probe. There were no instructions just this image. I believe this image was part of a LT appnote, but I can't remember which one. If the drawing make sense to you, would you mind explaining it to me. So I get there is a hollow brass tube, but I don't get how the pickup coil is attached and what it is attached to. Also how is the 50 ohm resister connected in this probe?
Thanks

 

[ericgibbs]

hi Mike,
Look here.
https://koti.kapsi.fi/jahonen/Electronics/Stuff/EMI_Sniffer_EDNMAG.pdf

Eric

 

[JimB]

OK, here is my interpretation of the drawing.

A brass tube connects to the body of a BNC connector.
The free end of the tube has one or more saw cuts, so that there is not a complete circumference to the tube.
A 50Ohm resistor connects to the pin of the BNC connector.
The free end of the resistor end near the saw cuts.
A 10 turn coil of wire is inserted axially into the brass tube, so that it is in the length of the saw cuts.
One end of the coil of wire connects to the free end of the resistor, the other end connects to the end of the brass tube.

The saw cut(s) in the brass tube prevent the tube from forming a shorted turn around the coil.
Because if the cut, the tube forms a Faraday Shield around the coil.

Does this help?

JimB

 

[JimB]

Powerful Google Foo there Eric!

JimB

 

[Mikebits]

Thanks a lot you guys, Really Helpful, I think I got it now. How you found that link Eric is beyond me

 

[ericgibbs]

How you found that link Eric is beyond me

I used: 'E-ric's M-ike's I-nquiry' Sniffer probe.

E