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COIL IDEA

A

Anonymous

Guest
I have an idea which is possibly not a very good one,so I thought it best to ask the experts before I waste my time building something that doesn't work.
If a central transmit coil has an overlapping receive coil on two opposite sides,can they both be nulled?If so,then isn't this an ideal way to cancel out ground effect and RFI while allowing a degree of discrimination.
I,m not sure that a null is required with PI but I think it would help.
Could something like this be used as a multi-
purpose PI-VLF ?
Sorry if this is really stupid,just an idea.
Any criticism gratefully received.
 
One of the beauties of PI is that it is easy to experiment with coils. As there is no tuning, the detector will work even if the turns, resistance, shape etc. are considerably off the optimum. Most PI
 
Thanks for your reply Eric.I Have the utmost respect for everything you say,but I must admit I envisaged having the two receive coils in phase.I was thinking of the circuit by David and Robert Crone,except instead of transmitting and receiving on both coils simultaneously I would try a separate transmit coil.It may well be totally pointless,I just thought that the response would be sharper and cleaner.
What I need,I suppose,is someone like yourself Eric,to release a good design into the public domain.Even discontinued commercial products never seem to be available for home constructors,but at least you personally share your vast experience with the rest of us and I thank you for that.
 
Hi Alan,
I have a recollection of the Crone design but don
 
Hi Eric
Here is a link to the Crone design. http://tthn.com/geotech/metdet/pi/twinloop.html
Earl
 
Hi Earl,
Many thanks. Can't seem to access the file though.
Eric.
 
I downloaded the same file Eric.It worked fine for
me using Acrobat reader 4
 
Hi Eric
It could be a problem with the version of Adobe. Version 4 seems to work ok. I had to upgrade to version 4 after having a similar problem trying to view a pdf over the web.
If you are having trouble downloading the file I can email it to you. It's 832k.
Earl
 
I had version 3.0 installed, but I downloaded Acrobat 5.0 yesterday and it works fine.
Eric.
 
Eric,
You are probaly reffering to a PSS-11 mine detector. The search head housing is square indeed, but the transmit windings are all circular. One big transmit coil and four receive ones. The main purpose of that layout was to obtain very narrow pinpoint capability, which is very important if a small metal content mine is to be removed. The signal nulls exactly at the target center. The PSS-11 was made in many variations, so maybe one of them had rectangular transmitt coil...
Piotr
 
Hi Piotr,
Many thanks for the information. I have only seen a picture of this detector and the shape of the TX coil was just an assumption. Just found lots of information and pictures at www.qsl.net/ke6myk/greenradio/pss-11.html
Eric.
 
Hi,
I have been working on this coil format for 5 years or so. It runs in antiphase mode (which can be switchable) . It does have a few quirks which can be ironed out. The main advantage is the ground balance (which a PI will do anyway) and structure balance (if you happento be sitting on top of a large ironstone rock).
This coil design can be used for IB or PI or a hybrid (which is what we are testing presently)
Good luck,
Greg
 
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