BFO "Discussion"

[Carl-NC]

Tim, one of the things I ask of people who disagree is civility in their disagreement. In re-reading through this thread, I see nothing from others that provoke the kinds of comments you're making in return. Please clean it up.

There is no corporate agenda here, just people discussing what interests them. BFO doesn't come up a whole lot (although it was one of the founding topics 15 years ago) and not a whole lot of people have direct experience with one. I own quite a few myself, but don't have access to ironstone ground to do the kind of test you suggest. I have no answer to your question, so I'm not going to speculate or make anything up. I do know that there are a handful of prospectors out there who still have a BFO in their arsenal because it can do select things that other detectors cannot do. Offhand I don't know what that is.

I do work for one of the major manufacturers, and the developments we choose to do are not rooted in a conspiracy against BFO technology. If BFO had promise and consumer demand, we'd do it. We just want to sell good products and make a profit. If you think BFO has a future, then maybe you're the guy to lead the way. I'm all ears/eyes, but I'm not gonna engage in whether people on this forum or in the corporations are trying to suppress BFO for some devious agenda. If ya got something to say, say it.

- Carl

[ivconic]

I cannot believe the corporate BS, so here are the originals. MY originals, in my handwriting. Circuit courtesy of Colin Mitchell. Instead of bagging and procrastination, make it for yourself.Your desktop simulations WILL NOT help.Covering my arse here. Gobble,gobble,gobble-turkey.
I have had it up to the back teeth with procrastinating WANKERS. Here and elsewhere.
Don't say-"Oh, I ran a simulation, and it didn't work".Just build the bloody thing![ATTACH]34017[/ATTACH][ATTACH]34018[/ATTACH]
The information purposefully omitted is so the brain-dead can't plagiarise.
Q, Eric and the other "gurus". Bow your heads in shame for your elitist and persecutory ignorance.

HOLLY COW!!!
Tim, that's the most original and most unbreakable method to protect own intellectual property that i've seen so far!!!
To draw a schematic like that!!!
Although i am eagle-eyed for such stuff; i am sure it will take me three months to decipher your art there!
Holly cow.... HOLLY BULL!!!!
http://www.animalsaustralia.org/feat...hp?ua_s=e-mail





P.S.
Holly kangaroo !!!

[kt315]

HOLLY COW!!!
Tim, that's the most original and most unbreakable method to protect own intellectual property that i've seen so far!!!
To draw a schematic like that!!!
Although i am eagle-eyed for such stuff; i am sure it will take me three months to decipher your art there!
Holly cow.... HOLLY BULL!!!!
http://www.animalsaustralia.org/feat...hp?ua_s=e-mail





P.S.
Holly kangaroo !!!

Your low leveled mental masturbations are degrading this forum much. STOP NOW IVITSA! anotherway I will ask the moderator BLOCK this thread!

[ivconic]

Your low leveled mental masturbations are degrading this forum much. STOP NOW IVITSA! anotherway I will ask the moderator BLOCK this thread!

Do ask!
Now!

[6666]

I've seen some pictures of iron stone rocks that had been broken open, to see why they had a random target response, and by chance they had small nuggets inside.
I have had a quick look through Colin Mitchell's website and your circuits look like an rf osc tx and a trf rx.

[ivconic]

I've seen some pictures of iron stone rocks that had been broken open, to see why they had a random target response, they had small nuggets inside.

In my country we are having sort of saying; "he poured them water in the ears"...
In English closest would be "pulling a leg" or similar...
Because now, with that statement; you opened "Pandora's box"... i tell ya!!!

(I can't resist from keep imagining bunch of a guys rushing back to desert and maniacally crushing all the "suspicious" rocks around, which they previously ignored!!)



P.S.
On the other hand; you might be right!
Than...

[Tim]

Glad to see I have finally got some intelligent responses here, through the hypocrisy, belittling and goading. Any animosity I perceived has only been duly responded to.

Yep it's base on a Colin Mitchell circuit..The receiver circuit is off the TA7642 datasheet, and the amp off the TDA2822 datasheet. No smoke and mirrors here boys. Just a bit of old-fashioned bush mechanics. You can probably tell by the chicken scratches on the paper even this took me a bit to work out.

Cobble another Colin circuit on and make a DD. Theres my IB. Circuit is a shunt-fed colpitts. Circuit 8 at Colins' Talking Electronics metal detector page.
The IB has a zip-zip on non-ferrous targets similar to the GMT.



Carl, it seems to me that nearly every thread since you suggested there was never any un-civil provocation, has been precisely that. Maybe it is not me you should be taking the big stick to.

[pebe]

Hi Tim,

I’ve been following this thread to see how your detector works. Now you have provided a circuit it all makes sense. It uses a variable oscillator whose frequency varies with the type of target. If it discriminates between ferrous and non-ferrous then the receiver must be frequency conscious. So I assume the receiver is tuned higher than the oscillator so when the target is non-ferrous the higher Tx frequency is detected on the sharp skirt of the rx response curve. But the non-ferrous target will increase the resonant frequency of both Tx and Rx, so does that not defeat the object of the exercise?

Also, as I am not familiar with all the metal detection terms, could you decrypt this jargon for me?

...Cobble another Colin circuit on and make a DD. Theres my IB. Circuit is a shunt-fed colpitts. Circuit 8 at Colins' Talking Electronics metal detector page.
The IB has a zip-zip on non-ferrous targets similar to the GMT.

Thanks.

[Tim]

Hi pebe. By assembling two of the said circuits, and using the coil described in Thomas Scarboroughs Matchless Metal Locator, the IB is made. You can also assemble the circuits, then place them near an AM radio to tune the coil/overlap position.
I have this circuit posted elsewhere, and someone said their simulator could not get the basic BFO to work, and they also said a simulator would not work for the IB tests. I don't know this though, as I don't use a simulator.
I am sure my receiving mechanism is frowned upon by the more adept here, and there are a plethora of better means. But with my limited knowledge I could not find one.
The 100R pot in the(one) coil-only circuit allows adjustment way below and way above the null point on the BFO, but when configured with the second oscillator circuit it can only tune the pre-set coils from null upwards. The setting of the DD coil position would need to be moved to the other side of null, to a ferrous sensitivity instead of non-ferrous, to have adjustment for ferrous detection, i.e the zip-zip on steel rather than gold, etc.

I have no software or programs to draw this circuit. I drew it on graph paper, traced and reversed it for the hole pattern on the copper board, then drew the etch with a sharpie.
Next investment is a laser printer.

I am greatful to all the positive respondants here. Maybe someone else can build and improve this circuit, if they can see the value of it.
I would dearly love to be able to make a print and silk template, but it is beyond my means.

Here is the paper trace for the IB I used. If anyone has the technology and the inclination, maybe they can clean it up and post a template for all.??
The black tracks from Rs to other side of caps are right, the original blue ones wrong.

[pebe]

Hi Tim. I'm afraid you've lost me. I think you are flipping between the circuit you have provided, and some other circuit with two oscillators in it. The circuit you show is not a BFO because there is only one oscillator and it has no other to beat with. But I'd would be interested to see the two circuits a la Thomas Scarborough.

I always use Microsoft 'Paint' (supplied with the OS) to draw circuits, and i believe there are many free programs to lay out PCBs.

[Tim]

If you left out the oscillator circuit in either the top left or top right of the trace, you would have my original bfo. The top left and top right are the two oscillators of the IB the remaining stuff is the AM receiver(as per TA7642 datasheet) and the components related to the TDA2822, in BTL mode amplifier circuit(as per TDA2822 datasheet). No ferrite receiver coil is shown. The connection points are top middle of trace. Reciever is 100mm x 10mmm ferrite with 45-50 winds. That connects to a 60pf trimmer and a 4-47pf variable trimmer, then through to the TA7642(lower left of centre), then through 4.7uf electrolytic to the amplifier circuit.
All of this could be substituted. It is the top left and top right that are the two oscillators of the IB.

Sorry, I forgot to mention bottom right is LM317 regulator supplying the 1.2 volts to TA7642 and related AM receiver components. The rest runs 9 volt.

[pebe]

I was referring to this circuit, and I can only see one oscillator.
http://www.geotech1.com/forums/attac...7&d=1445091156
Adding another one to make an IB detector is a bit vague, ie. coil couplings etc.

So I'll stay with my own design that I have started making.

[Tim]

Yep, I only drew one. That was the original BFO I assembled on a breadboard. It was only after assembling the Matchless and its' coil that I had the idea to make a second oscillator and hook up the Matchless coil, thus turning a BFO into an IB. That is the tracing paper circuit.

[WM6]

I was referring to this circuit, and I can only see one oscillator.
http://www.geotech1.com/forums/attac...7&d=1445091156
Adding another one to make an IB detector is a bit vague, ie. coil couplings etc.

So I'll stay with my own design that I have started making.

Some BFO designs as second (fixed frequency) oscillator use regular AM radio tuned at the same frequency as first sensing oscillator.
This is the case with Tim's oscillator named "Cuircuit 8" and taken out of "talking electronics" web site.

But Tim is go further and doubled "Circuit 8" oscillator to make BFO/IB detector and replaced AM radio as second oscillator with some other solution.
Basically his new BFO/IB design, on sensing oscillators side, looks like this:



Transistors are not critical almost any universal NPN will work here as par example 2N3904, 2n2222, BC184 etc.

If AM radio is not used as fixed oscillator stage, then you can go down with frequency even under 100kHz.

[Tim]

WOW! That's great WM6. You do me a great service explaining it so well!!! I am sure Colin Mitchell would also be impressed. Perhaps now we can further this into a worthwhile open project. This setup with 40 turns, .25mm enamelled, 15cm diameter, will give 110khz.
And this is something a rank amatuer can make without big dollar investment.
Perhaps now, with WM6's brilliant diagram we can generate enough interest to develop the receiver and a board.

BRAVO!