field off a coil

[golfnut]

I am aware that the field on a coil is a ring donut.


This means the centre area of the coil give the least field?


steve

[Qiaozhi]

I am aware that the field on a coil is a ring donut.


This means the centre area of the coil give the least field?


steve

The reason the two coils need to be overlapped is to reduce the coupling between the TX and RX coils. The search head acts like a transformer with weakly coupled primary and secondary windings; and the target acts like the core of a transformer, effectively coupling some of the TX energy into the RX coil. With the arrangement you have shown, the receiver will be swamped by the TX signal. Try reading the "Coil Basics" article here ->
http://www.geotech1.com/cgi-bin/page...&file=info.dat

[golfnut]

Sorry I wasnt clear here

The circles are the radiation.reception pattern. The line in middle a coil side on.

I guess there would not be advantage having loop vertical - didnt think it thru..



More Ant background

http://www.aa5tb.com/loop.html

http://www.iw5edi.com/ham-radio/file...p_antennas.pdf

http://www.vlf.it/lowfloop/lowfloop.htm

S

[Carl-NC]

You're looking at the far-field radiation pattern of a loop antenna. Detectors use the near-field magnetic field, which is different.