BFO/IB cross mod info needed

[satdaveuk]

Hi can one of you tech guys help me on this simple self build one.
the detector tunes with a 100pf varable capacitor, but i like to replace with a pot.
it runs at 10khz approx.
I wanted to attach my circuit on here but i see no provision , anyway any tips would be handy

Many thanks

Dave

[WM6]

I wanted to attach my circuit on here but i see no provision , anyway any tips would be handy

Don't go desperate, try again.

[Qiaozhi]

Hi can one of you tech guys help me on this simple self build one.
the detector tunes with a 100pf varable capacitor, but i like to replace with a pot.
it runs at 10khz approx.
I wanted to attach my circuit on here but i see no provision , anyway any tips would be handy

Many thanks

Dave

You need to make at least one post before you are allowed to attach any images. You have just done that, so please try again.

[satdaveuk]

You need to make at least one post before you are allowed to attach any images. You have just done that, so please try again.

Ok thanks, heres the diagram

[WM6]

the detector tunes with a 100pf varable capacitor, but i like to replace with a pot.
it runs at 10khz approx.

Something for mikebg.

[satdaveuk]

Thanks WM6
Hope he sees it

[mikebg]

Satdave, you should learn how to use "Prnt scrn" key of your computer.
WM6, you should know that I have allergy and intolerance for circuits designed by Rev. Thomas Scarborough.

[satdaveuk]

Satdave, you should learn how to use "Prnt scrn" key of your computer.
WM6, you should know that I have allergy and intolerance for circuits designed by Rev. Thomas Scarborough.

So i take it thats a no then lol

[maikl]

Hi satdaveuk. Why did you go the hard way: computer monitor are photographed with a digital camera? Scheme to your photo is BB metal detector by Thomas Scarborough. For this design has to be put varable approximately 100pF capacitor and the same can you find in old radio receivers. BB metal detector is a "toy" and not for real hunting.

[Qiaozhi]

So i take it thats a no then lol

If you are planning to build this circuit in order to learn how metal detectors work, then go ahead. But if you are thinking of using it for some real treasure hunting, you would better advised to look here ->
http://www.geotech1.com/cgi-bin/page...e=projects.dat
and build something more worthwhile.

[mikebg]

If you are planning to build this circuit in order to learn how metal detectors work, then go ahead. But if you are thinking of using it for some real treasure hunting, you would better advised to look here ->
http://www.geotech1.com/cgi-bin/page...e=projects.dat
and build something more worthwhile.

Qiaozhi, I wish learn how metal detectors work. Can you explain me using this circuit diagram?

[Qiaozhi]

Qiaozhi, I wish learn how metal detectors work. Can you explain me using this circuit diagram?

I know you think the circuit is crap, but beginners have to start somewhere.

[Skippy]

I think the idea is you build this from bits you have lying around, such as the tuning capacitor from an 'Olde Wireless set'. Trying to change it to a varicap diode tuned device is not the idea.
There are other simple BFO designs around, including some availabe on this site.
From an educational perspective, the key to understanding the circuit is realising the capacitor is adjustable from +100pF to -100pF. These devices can be found in scrap time-machines, continuum transfunctioners, good perpetual-motion machines, etc!

[satdaveuk]

Hi satdaveuk. Why did you go the hard way: computer monitor are photographed with a digital camera? Scheme to your photo is BB metal detector by Thomas Scarborough. For this design has to be put varable approximately 100pF capacitor and the same can you find in old radio receivers. BB metal detector is a "toy" and not for real hunting.

Hi
I think you all have the wrong end of the stick
I had already built this ages ago and it works, it was never built to go out and metal detect, it was built to show my kids how simple a basic metal detector could be knocked together.
All i asked was... How could I replace the 100pf tunning cap, for a pot.
Now if you dont know how to do it, then just say so, and let someone come on here that does know.

Its just a bench project nothing more nothing less
Regards
Dave

[maikl]

Hi satdaveuk. I have the impression that you're a little angry. Here is your version of BB metal detectors without a variable capacitor: