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Offline Lingote
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« Reply #80 on: April 28, 2013, 05:34:24 pm »
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Amable Foro Hunting.com : Quisiera obtener el diagrama esquemático de este detector BFO discriminador que envía Cornelio por E-mail. Pregunto: ¿Debo publicar mi dirección?. Seguro que no. Cordiales saludos y gracias. Lingote.


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« Reply #81 on: April 28, 2013, 06:14:39 pm »
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Welcome to the Forum!      We are a English Only forum.

Please post the same.

Bablefish:   A:Friendly Forum Hunting.com: I would like to get the schematic diagram of this Screener BFO detector that sent Cornelius by E-mail. Question: do I publish my address?. Surely not. Best regards and thank you. Ingot.

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« Reply #82 on: April 29, 2013, 01:38:09 am »
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If I remember all the info is on this thread but there were some problems with the  schematic

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So many questions so little time

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« Reply #83 on: May 21, 2013, 04:27:40 pm »
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Gracias Cornelio por proporcionarnos tan claramente los datos para construir el Detector BFO discriminador. Ya mismo salgo a hacer acopio de los componente necesarios. Cuando esté en uso les haré llegar noticias. Cordiales saludos a la comunidad de Thunting.com

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« Reply #84 on: May 21, 2013, 04:47:45 pm »
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Quote:Posted by Lingote
Gracias Cornelio por proporcionarnos tan claramente los datos para construir el Detector BFO discriminador. Ya mismo salgo a hacer acopio de los componente necesarios. Cuando esté en uso les haré llegar noticias. Cordiales saludos a la comunidad de Thunting.com

English only, please. This forum is English only.

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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.
Let's Talk Treasure!

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« Reply #85 on: May 21, 2013, 05:01:38 pm »
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Never understood this circuit.   All BFO's are discriminatory to a Point.    All Can tell you if it's Mineral or Metal.

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« Reply #86 on: May 22, 2013, 12:23:23 am »
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Explanation in frequency domain:
All CW metal detectors are discriminatory until a frequency fr.
The 'r' is subscript meaning resonance. At this frequency, the phase difference of received signal relative to current in TX coil is zero. This is illustrated below with loci in complex (impedance) plane. The frequency fr depends on eddy size of target made of ferrous metal. Operating above frequency fr, the metal detector can not tell you if the metal of target is ferrous because it sees all metal targets as nonferrous.

Here is an explanation in time domain:
All PI metal detectors are disciminatory above a sample delay tr. The tr depends on eddy diameter of the ferrous metal target. Subscript 'r' means resonance because at this delay the odd part of decay curve is equal to its even part. When the sample delay is less than tr, the metal detector can not tell you if the metal of target is ferrous because it sees all metal targets as nonferrous.

Explanation of loci in impedance plane:
The phase of TX current is represented with Re axis.
1. Locus of lossless ferrite. It is not shown because coincidents with Im axis. The signal has 90 deg phase angle for all frequencies.
2. Locus of lossy ferrite is also a straight line. The signal has less than 90 deg phase angle and it is constant for all frequencies.
3. Locus of nonferrous metal. The signal has negative phase angle for all frequencies. Point C represents cutoff frequency at which the phase angle is minus 45 deg.
4. Locus of ferrous metal. It is created by combination of loci 2 and 3. Point Q represents the resonance frequency. Point D appears in mirror position of cutoff frequency (phase angle +45 deg).

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Offline GoldDigger1950
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« Reply #87 on: May 22, 2013, 08:17:44 am »
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Quote:Posted by mikebg
Explanation

Great to see you back, Mike. Just visiting or are you staying a while?

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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.
Let's Talk Treasure!

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« Reply #88 on: May 22, 2013, 03:39:06 pm »
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Hi GD,
Since you are " the old men and the soil", I think you know how the soil distorts the target signal.
Recently I was in other forums to explain why the soil convolutes target signal and why the software of metal detector should make deconvolution. Please read these threads to see how the "great inventors" can't understand something known since 19-th century:

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http://www.geotech1.com/forums/showthread.php?20264-Ground-Balance-Theory&p=168451#post168451


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http://australianelectronicgoldprospectingforum.com/electromagnetics-and-em-fields/if-you-are-into-complex-maths
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Offline pandoraguru
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« Reply #89 on: June 09, 2014, 05:09:38 am »
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Hi Cornelius

I might be interested to in this BFO detector, can you send me a copy of the full schematic?
Thank you!

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