Audio feedback is it the answer?

[sa1ka]

Well, thanks for all of the help in making my first OO coil. I am well on my way, my TX coil measures right on where it should. The RX is off a bit but close enough to work.

My next question:

Why has no one built a detector that has just a modulated/raw audio? Why I ask this is, last year I recorded the audio output from several different types of detectors, non tone id, and noticed some very interesting things. Different materials gave different wave forms. Different objects did the same.

I started this investigation because I along with other THers can often say "I could just hear the difference in tone and new it was ....." My initial observations concluded that there was some validity to these comments and not just a sense of euphoria over finding a nice silver coin. Many of the older style machines do this better than newer designs. This would not replace the disc circuit, who wants to listen iron all day?

I am not an electronics guru by any stretch of the imagination but wonder if it would be possible to create such a detector that gives an audio profile of the signal generated by the detected object. Ideally to see the wave pattern on an LCD screen would go a long way to know what you are hearing.

Please forgive any incorrect terms, hopefully you understand what I am asking here.

[Max]

Well, thanks for all of the help in making my first OO coil. I am well on my way, my TX coil measures right on where it should. The RX is off a bit but close enough to work.

My next question:

Why has no one built a detector that has just a modulated/raw audio? Why I ask this is, last year I recorded the audio output from several different types of detectors, non tone id, and noticed some very interesting things. Different materials gave different wave forms. Different objects did the same.

I started this investigation because I along with other THers can often say "I could just hear the difference in tone and new it was ....." My initial observations concluded that there was some validity to these comments and not just a sense of euphoria over finding a nice silver coin. Many of the older style machines do this better than newer designs. This would not replace the disc circuit, who wants to listen iron all day?

I am not an electronics guru by any stretch of the imagination but wonder if it would be possible to create such a detector that gives an audio profile of the signal generated by the detected object. Ideally to see the wave pattern on an LCD screen would go a long way to know what you are hearing.

Please forgive any incorrect terms, hopefully you understand what I am asking here.

Hi,
answer is: commercial.
In older e.g. off-resonance, BFO and also some vlf-pll-bfo machines there was what you mentioned...so commercial take place...
You know...metal detectiong and THing is considered by manifactures like any business...so they need to expand market and number of users...so decided to switch from something that just some people could (really) use with confidence to the flat response of a buzzer.

That's all. Any IB design today could implement what you are asking for...but most of the times is on display (if any) that you would see if it's silver or ...trash. OK...there are still now some multi-tone id machines...but few now (some tesoro's still around you can find on ebay are really multi-tone).

Problem is that sometime tone id is just confusing and don't give the information you need. Old machines were "brutal" but you may say: ops ...this is silver just using your ear. Most of them are still used (and valuable) today.

Best regards,
Max

[sa1ka]

Hi,
answer is: commercial.
In older e.g. off-resonance, BFO and also some vlf-pll-bfo machines there was what you mentioned...so commercial take place...
You know...metal detectiong and THing is considered by manifactures like any business...so they need to expand market and number of users...so decided to switch from something that just some people could (really) use with confidence to the flat response of a buzzer.

That's all. Any IB design today could implement what you are asking for...but most of the times is on display (if any) that you would see if it's silver or ...trash. OK...there are still now some multi-tone id machines...but few now (some tesoro's still around you can find on ebay are really multi-tone).

Problem is that sometime tone id is just confusing and don't give the information you need. Old machines were "brutal" but you may say: ops ...this is silver just using your ear. Most of them are still used (and valuable) today.

Best regards,
Max

Thanks Max, tone ID is not what I want but a true tone generated by the target, beep circuits don't excite me very much. Is there a basic circuit design that would work for this, even without any discrimination for now? What manufactured machine would you recommend? I think that many of these older type of machines could be just as good today with maybe a change in the frequency, components being used as well as some modern coil construction. I do like Tesoro machines.

As for confusing, I don't think that people are digging that many more good targets than in the old days, with confidence, than when you had to learn your machine more. I agree that 20 years ago hunting was much better, fewer hunters and many more shallow, silver coins than now.

As coins get deeper discrimination becomes less effective, I wonder whether the target profile will change that much, if it were interpreted by the way I suggest.

After collecting many samples we were able to see similarities between target type and materials. With some mathematics, a database and some software to compare the signatures I would think that this would be possible. After all is this not similar to how military sonar/radar works?

Just the ramblings of a fool, thank you for your tolerance.

[Max]

Thanks Max, tone ID is not what I want but a true tone generated by the target, beep circuits don't excite me very much. Is there a basic circuit design that would work for this, even without any discrimination for now? What manufactured machine would you recommend? I think that many of these older type of machines could be just as good today with maybe a change in the frequency, components being used as well as some modern coil construction. I do like Tesoro machines.

As for confusing, I don't think that people are digging that many more good targets than in the old days, with confidence, than when you had to learn your machine more. I agree that 20 years ago hunting was much better, fewer hunters and many more shallow, silver coins than now.

As coins get deeper discrimination becomes less effective, I wonder whether the target profile will change that much, if it were interpreted by the way I suggest.

After collecting many samples we were able to see similarities between target type and materials. With some mathematics, a database and some software to compare the signatures I would think that this would be possible. After all is this not similar to how military sonar/radar works?

Just the ramblings of a fool, thank you for your tolerance.

Hi,
don't know if there are still in production today real bfo or off-resonance or continuos-tone-variation vlf-pll. But there were many in the past...also many kits e.g. from UK magazines and others all around the Europe. If you think at very old...well also Jetco machines are this way. Problem is I remember that good ones are really few...and costs (at that time) some thousand £. Most well eng units came from UK but I can't remember from wich manifacturer... cause at that time I was a child. I've seen two in that years but not owned any... one was bought by my father and two friends (costs was something 1000 or 2000£) ...and was disc + continuos tone and the other was a straight continuos tone too but I think was an off-resonance type... bought by my father's friend. I can't remember exactly what they are...and my father too...but expecially the second one and its owner was legendary here...cause he can find what's in the ground just by earing the signal in the headphone...so before digging. As I remember there was problems with bricks...cause sometimes he get confusing signals from them...but the rest of the times he get what he said it will be!
The frequency variations in tone is given by change in inductance in the coil...the tuned circuit change frequency and that is detected by etherodyne stages or other similar circuits (most BFO and off-resonance work like this). In PLL-VLF frequency used are lower (to contain gnd effects and skin effects e.g. on foil) but circuit are quite different. I know that there are also ibrid ones...IB that used same principles.

Best regards,
Max