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Offline japanese
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« Reply #10 on: May 31, 2011, 10:30:32 am »
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Hi homefire
               This file may help.
best time
j.

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Offline Homefire
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« Reply #11 on: May 31, 2011, 10:34:39 am »
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WOW!  Thank you.   I can play with that on for sure.

Photo Copy and Transfer is in order.

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Offline dr.jare
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« Reply #12 on: May 31, 2011, 12:58:56 pm »
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The disadvantage is increased weight and for the same inductance coil gives greater resistance coil. Resistance is also a big deal but it is a neglected. The advantage is greater sensitivity to small items.

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Offline Eugene52
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« Reply #13 on: May 31, 2011, 01:31:54 pm »
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Quote:Posted by dr.jare
The disadvantage is increased weight and for the same inductance coil gives greater resistance coil. Resistance is also a big deal but it is a neglected. The advantage is greater sensitivity to small items.


I agree !! The deep detection depth is reduced by the smaller magnetic field [reduced current] .
The pc coils are only good for other applications like the smallest of targets .

HH.................Eugene

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« Last Edit: May 31, 2011, 01:34:24 pm by Eugene52 »
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Offline Homefire
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« Reply #14 on: May 31, 2011, 01:37:25 pm »
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Like little gold Nuggets!  LOL!   Cool

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Offline Eugene52
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« Reply #15 on: May 31, 2011, 01:48:37 pm »
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Quote:Posted by homefire
Like little gold Nuggets!  LOL!   Cool


Yes Mr. HF  !!! The other real big reason PCB coils are made is that they are much cheaper to
manufacture . No coil form or foam , hey that saves 59 cents a coil times 10,000 equals a week-end yacht ride for the CEO and his lovely secretary !!!  Shocked

HH...........Eugene

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« Reply #16 on: May 31, 2011, 01:53:24 pm »
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Sounds about right.   Sorta like a certain manufacture that didn't put a volume control on one of there hottest selling detectors.

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Offline GoldDigger1950
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« Reply #17 on: May 31, 2011, 03:22:23 pm »
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The interaction of the current in a coil is the wire to wire field build up and in a PCB, this is minimal giving you much decreased power for the purpose of transmission. On the receiver side, it gives greater surface area facing the signal returning from the target which is ideal.

Thus, the conclusion I reach is that the TX coil should be a standard wire wound coil and the receiver coil is coin toss with a leaning towards a PCB coil.

Not suitable for PI use at all.

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« Reply #18 on: May 31, 2011, 04:17:04 pm »
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Hey GD what would be the result if you wher to take say the outside 10 turns and make 3 boards out of scissor cut board material and connect them together.  Would you now have a 3 deep stack with the equivalent of a 30 turn coil?  What would the "L" be and would the power out and sensitivity work out.




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Offline GoldDigger1950
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« Reply #19 on: June 18, 2011, 11:04:25 pm »
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Gramps, I'm fairly certain that a coil made from the material on a PC board would be too small an inductor for which to apply transmit power. In order to make it work, the thickness of the foil should be greater than the width making the etch very, very thin. Then, the traces have to be close together in a spiral configuration. None of that is ideal for a transmit coil. You need real beef for that. In a PI detector, for example, the peak voltage might be as high as 400 volts due to the buck-boost configuration of the output pulse circuitry. The receiver, on the other hand, would benefit from a spiral configured coil with its widest surface facing the signal. Remember, in spite of it being a tuned circuit, a receiver coil is still an audio frequency antenna.

For audio frequency coils, stick with wire.

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It's all about that moment when metal that hasn't seen the light of day for generations frees itself from the soil and presents itself to me.
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