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Offline giuhalftrack
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« Reply #40 on: October 24, 2018, 03:33:32 am »
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The original PCBs are not so good with modern package component unless you have "axial lead" style packages, i'm on the process to design new PCBs, hera a preview of the TX PCB with old style connections Smiley

The dimensions are greatly reduced from the original.



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« Reply #41 on: October 24, 2018, 08:44:00 am »
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  Dang, You're going whole hog on this thing.  Going to go with FET's  in the mixer section ?

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Offline giuhalftrack
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« Reply #42 on: October 25, 2018, 01:44:46 am »
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Quote:Posted by Homefire
  Dang, You're going whole hog on this thing.  Going to go with FET's  in the mixer section ?


I'm thinking at a way to eliminate the L2 inductor... probably i will try a gyrator...
consider that I'm always in learning process (despite my avatar  Grin) so i don't have understand about the "FET mixer" ...do you refer to have a mixer with hight input impedence ?

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« Reply #43 on: October 25, 2018, 09:24:38 pm »
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      No not the impedance issue.  FETS make SORRY MIXERS !   LOL    FET's are not so good in the linearity aspect.  They produce High Level and strong Harmonics Products.    Bad Stuff in most other Mixer applications.   Good Stuff in a BFO.  

"" The advantage of active FET mixers is that they provide a conversion gain rather than a conversion loss. The disadvantage is that their linearity is not as high as that of a passive or switching mixer circuit. Field effect transistors are widely used within RF mixer circuits.
FET Mixer :: Radio-Electronics.Com""

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Offline giuhalftrack
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« Reply #44 on: October 26, 2018, 02:22:17 am »
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Quote:Posted by Homefire
     No not the impedance issue.  FETS make SORRY MIXERS !   LOL    FET's are not so good in the linearity aspect.  They produce High Level and strong Harmonics Products.    Bad Stuff in most other Mixer applications.   Good Stuff in a BFO.  

"" The advantage of active FET mixers is that they provide a conversion gain rather than a conversion loss. The disadvantage is that their linearity is not as high as that of a passive or switching mixer circuit. Field effect transistors are widely used within RF mixer circuits.
FET Mixer :: Radio-Electronics.Com""


Interesting !!! I'll take informations about this subject.

Yesterday I tune the detector and made a few tries with different target... I was amazed when i could detect a gold earring of 10 mm (open circle "no a true ring" Wink ) diameter from 15 cm of distance !!!
I know this is an air test and probably the 475 KHz freqeuncy does a lot of skin effect... I must test this in real ground, i aspect a very reduced performance when ground minerals will be excited by 475 KHz so probably it's impossible to detect the gold target when buried.

I'm happy with this project !!! I'm learning more and more electronic.

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« Last Edit: October 26, 2018, 02:26:55 am by giuhalftrack »
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Offline giuhalftrack
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« Reply #45 on: July 08, 2019, 08:30:49 am »
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I everibody
I start to collect the material regarding this project, I've made a video on my channel about this detector, as soon as I can I'll go out to use the unit in the woods, hoping that a BFO
could find some "big deep target" (WWII stuff)

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