How this circuit like?

[homefire]

Someone over in china must be smart as hell!

They have the Jobs and we here in the USA don't have squat!

My first detector was a BFO, and had to adjust it every 20 seconds or so.

I found a silver quarter with it at 8" 20 minutes after taking it out of the box.

That one was based on LC tank circuits ran at 360KHz.

Using Quasi Digital circuits and Crystal controlled Ref Osc you have another Ball game.

Too Simple but cool.

http://www.extremecircuits.net/2010/...ocator_13.html

http://www.hobby-hour.com/electronic..._detectors.php

[mikebg]

Homefire, please read my posting #7 to understand why the circuits in your links are primitive. Posting #7 contains information for design of modern BFO type metal detectors, but it is only a part of design principle. The problem is how to design amplifier used in search oscillator.

The following description of improved principle for search oscillator is not to **** KT315 and Maikl that BFO metal detector has future, but is just continuation of analysis started with posting # 13. Those who believe that the principle of metal detecting with search oscillator (BFO) has no future, should be interested what principle has a future. Let we analyse the best operating principle for a future MD without search oscillator. I described three main things of this principle in posting #13.

Let continue with question "How to classify a BFO metal detector in frequency domain if there are only two types? Whether BFO is narrow band or wide band?"

The TX coil of search oscillator creates magnetic field with "noise induction". In oscope (in time domain), noise induction seems different from sine induction and pulse induction, but how seems frequency spectrum of noise? As you know the noises are different in "color". Wide band means "white" noise.

We can design a metal detector using white noise generator to drive TX end stage. The TX will operate without oscillation. The BFO MD is specific case of this design because instead noise generator we use an amplifier having very high gain. The gain can not be achieved using in amplifier only one transistor. Our amplifier should amplify internal thermal noise until output starts to saturate.

Let we use in search oscillator an amplifier with adjustable bandwidth and gain. Imagine a MODE switch having two positions: NARROW BAND and WIDE BAND. How seems output of such amplifier at different modes when feedback is disconnected. It can not oscillate.

The left figure of attached image shows output when MODE switch is in position WIDE BAND. The gain is increased until output starts to saturate. The noise seems as a band thick no more than 1/8 to 1/6 of distance between saturation thresholds.

The right figure shows output signal at NARROW BAND position. We should increase the gain to obtain operation near to saturation. This is most important effect of narrow band operation because increased gain means increased sensitivity. The visual effect is as if there is a chaotic modulated oscillation, but in reality is amplified noise at a narrow band.

After we designed a search oscillator operating as narrow band or as wide band metal detector, remains to write in the operator's manual when BFO MD should operate with MODE switch in position NARROW BAND and when in position WIDE BAND. Since this question is as quiz relating not only to BFO but to all kinds metal detectors, I will put discussion also in section "General Electronics". The title of this thread will be something like "Block diagram of RX for ultimate metal detectors" or something more short.

[mikebg]

fascists, you mean hazi here probably, gave people the work places, got up the economic, developed the industry. now I have not the work! I have been retired without my wish! so think what you write about.

Dear KT315,
Accept my apologies, that I judged you as fascist and Nazi, but I was misled by a website that everyone can see:

http://www.reibert.info/forum/showthread.php?t=83723

The information for you is in Russian:
Место жительства: Литва
Интересы: антропология. социальная инженерия и философия. поиск рационального зерна, во всем.
Профессия: технарь
Дата рождения: 8 Янв. 1962
Регистрация: 10.04.2005
Всего сообщений: 593

Translated in English:
Location: Lithuania
Interests: anthropology. social engineering and philosophy. Search of truth in all.
Occupation: geek
Date of birth: 8 January 1962
Registration: 10.04.2005
Total Posts: 593

I do not read everything carefully, although I know well Russian. In reality the site offered for sale items from World War II. In that forum you are only a seller of such targets.

The reason for my confusion was that each participant in the forum had any fascist military rank, that's why I composed the following portrait for you:

[mikebg]

Below attached is the page with translation in English.

[kt315]

[mikebg]

Sieg Heil, Herr General!

[kt315]

your General and his unterfeldwebel Alex are ready to trip in Bulgaria at SUNNY BEACHES! tu-tuuuu!!

[mikebg]

your General and his unterfeldwebel Alex are ready to trip in Bulgaria at SUNNY BEACHES! tu-tuuuu!!

Анатолий, если говорить серьезно, в Болгарии, в сентябре погода, как правило, хорошая, теплая и устойчивая, а цены на гостиницы значительно сокращены. Прогноз является то, что погода будет хорошей до понедельника. Более отдаленные прогнозы метеорологов не дают. Мы вернулись с моря потому что с вчера дети на школе.

[maikl]

kt315 like your avatar "general Ratko Mladic" you're my brother, a Serb. Lithuanians were never fascists and aggressors. Unlike some other people who were always on the side of the fascists and the occupier (in the first and second world war...). mikebg wrong one hundred kidding kt315. kt315 contributed greatly to Geotech (sometimes in their own strange way). kt315 give the direct answers and schematic not entangled graphs and philosophical answers unlike some. Best regards and to get serious not to be children.

[mikebg]

Maikl, note that KT315 and I know Russian.
Search WEB for his both names "Анатолий Кутовой" and for my both names "Михаил Волков" to see how many people in Russia have such names.
In Serbia, Russia and Bulgaria used the same alphabet and our languages are so close that if everyone spoke in his native language, we'll get along without an interpreter. We will always feel not only as cousins but as brothers in Christian religion. Despite I'm not religious at all and not go to church, I cling to one important value of the Christian religion that says: LOVE THY NEIGHBOR!
So I feel hatred towards people that although Europeans and Christians, violate that God's commandment. Nazis and fascists are most violated that God's commandment during WWII. Most of these criminals must have been religious, and must have gone to church before and after making a crime to humanity.
European values are required to treat with love and respect for all, regardless of which country they were born, regardless of what knowledge they have, regardless of which party they are forced to join.

[Qiaozhi]

Maikl, note that KT315 and I know Russian.
Search WEB for his both names "Анатолий Кутовой" and for my both names "Михаил Волков" to see how many people in Russia have such names.
In Serbia, Russia and Bulgaria used the same alphabet and our languages are so close that if everyone spoke in his native language, we'll get along without an interpreter. We will always feel not only as cousins but as brothers in Christian religion. Despite I'm not religious at all and not go to church, I cling to one important value of the Christian religion that says: LOVE THY NEIGHBOR!
So I feel hatred towards people that although Europeans and Christians, violate that God's commandment. Nazis and fascists are most violated that God's commandment during WWII. Most of these criminals must have been religious, and must have gone to church before and after making a crime to humanity.
European values are required to treat with love and respect for all, regardless of which country they were born, regardless of what knowledge they have, regardless of which party they are forced to join.

Although I agree with your post, please can we terminate this discussion and return to the main topic of this thread. Remember that you are in the Schematics Forum.

Political and religious discussions have a bad habit of rapidly becoming heated, and Geotech is not the place for this.

Thanks for your understanding.