Shield the E-probe?
#8
(2017-10-15, 17:42)KY5G Wrote: Based on the Pesky Project gallery pics/text, and the current shipping ferrite core diameter of approx 10mm (actual core, not as wrapped and heatshrink added), the spacing between the outside of the core and the shield should be approx. 10mm x 10 (stated multiple) = 100mm

1) Is 100 mm correct?

2) Would a round shield housing offer any benefit over a square housing?  Obviously, square is easier to construct/prototype, but I'm asking about performance...

3) The gap distance shown is 2-4 mm...  That's a pretty big range...  What is the theory behind sizing the gap?  Would it be based on the frequency and polarization of the "noise" vs. "desired" signal?
3a) Does the gap function as an admission aperture?

4) How should the gap be oriented?  Does it matter? Say a ferrite that is long axis oriented E/W to generally receive N/S signals....  Gap Up? Down? North? South?

4a) Would there be any benefit (on horizontally oriented ferrites rcving vert polarized sigs) to having TWO gaps oriented in the 2 cardinal directions the ferrite favors?  (Of course, you'd need to bong GND to both halves, or bond the halves together at both ends on the "far side".

5) When using the third ferrite oriented vertically, which would favor receiving horizontally polarized signals, how would you orient the gap? How many gaps?  1, 2, 4?  Intuitively, I'm lead toward 4 as a minimum... oriented N,S,E,W...  Or 6, oriented every 60 degrees.... Or 8, every 45....  How many gaps before the shield is rendered less than useful.

Crap....  it just occurred to me that I am too ignorant of the basics in this particular subject to converse intelligently about shield theory, design, optimization for H-filed ferrite antennas.
It would appear I have just added a couple thousand pages of reading to my list...  Wink
First, shielding does NOTHING for Magnetic components... it's only an attempt to minimize an Electric component. I ran for a couple of years with NO shielding, since my junk is all Magnetic,
with very little E noise.  The Pesky was tried for one specific electric troublemaker, and it worked, where other approaches and types did not.

1. 10 X Diameter of the Core is the WIDTH of a Side... The Antenna is centered inside, so there would be 37.5MM from core center to side. Don't ask me why. There's probably some math to compute, but this is what the Engineers told us to use on that ECM COMM gadget.
2  Any thin gap width would probably work. My notes specified 2-4mm for the project we were working on at the time... some engineer said it., and it was in the L and S communications bands.
3. All kinds of shielding approaches.... First Question:  If you don't have electrical interference being picked up by the H field antenna's you probably don't need any????
4. Gap runs along axis of rod.
4a. Not on a ferrite core... nothing works for me for H polarized in my environment,. 
5.  Only need one gap if you need any shielding at all. the gap is to keep from 'shorting' the shield, and possibly degrading reception.

Re: "Crap" ... How do you reckon the rest of us learned anything? Big Grin   Ask away!  
If we don't know the answer, we'll invent something, maybe. Angel
Confusion and lack of knowledge is easily fixed,...
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Messages In This Thread
Shield the E-probe? - by Max_Headroom - 2017-04-22, 14:54
RE: Shield the E-probe? - by cutty - 2017-04-22, 15:57
RE: Shield the E-probe? - by Max_Headroom - 2017-04-29, 14:16
RE: Shield the E-probe? - by RichoAnd - 2017-04-29, 15:19
RE: Shield the E-probe? - by Max_Headroom - 2017-04-29, 18:34
RE: Shield the E-probe? - by KY5G - 2017-10-15, 17:42
RE: Shield the E-probe? - by readbueno - 2017-10-15, 19:26
RE: Shield the E-probe? - by cutty - 2017-10-15, 21:11
RE: Shield the E-probe? - by KY5G - 2017-10-16, 22:05
RE: Shield the E-probe? - by cutty - 2017-10-16, 23:34
RE: Shield the E-probe? - by KY5G - 2017-11-01, 17:54
RE: Shield the E-probe? - by RichoAnd - 2017-10-17, 05:44
RE: Shield the E-probe? - by KY5G - 2017-11-01, 18:01

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