2 boxxxx :)

[erolunall]

Hello Mikebg

Could you give detailed schermatic pcb coil radio brand etc.

Happy new year to all of members of mad detector scientists.

Regards
Erol

[mikebg]

Tis is a virtual project only

Hi Erol,
All available information on Okantex System is located in postings on the aforementioned two threads. You read them?
REMI group is currently trying to gather as much information to understand the principles of Okantex System.
The lowest frequency which can operate the system unit U2 (receiver) is 150KHz, and the narrowest bandwidth is 4KHz. These data are too high and not favorable for the detection of metals.
The 150KHz frequency is too high because it gets very strong signal from the ground, coinciding with the phase of signal from a metal object.
The 4KHz bandwidth is unnecessarily large because it gets too strong thermal noise. For action of a CW metal detector is sufficient bandwidth only 12Hz, but there are detectors working with even 4Hz band width! This means sqrt (4000 / 4) = 31 times less noise!

[mikebg]

What contains U1?

The key to solving Okantex System is unit U3 (box Buzzer or Audio). The box U3 is required only if TX broadcasts CW (continous wave - unmodulated signal or Sine Induction). Its task is to provide as sound the demodulated signals whose spectral composition (from DC to 4Hz) is not perceived by human hearing. As with conventional metal detectors, the box Audio must contain the amplitude or frequency modulator that processes the DS (demodulated signal) and a carrier frequency from audio frequency generator or multivibrator.
The most appropriate place to connect the audio unit U3, is the DC amplifier for DS signal as was shown in posting #512.
From this explanation follows that the unit U1 is TX for CW 150KHz. We can design a low power TX for 150KHz with a ferrite TX antenna. So we can to restore Okantex System, but will keep its shortcomings:
- High operating frequency 150KHz,
- Expensive, heavy and bulky RX box,
- A higher level of noise and interferences due large 4KHz bandwidth of RX.
I've already received proposals from radio amateurs to design a more sophisticated version - Okantex System V2, which consists of:
1. Stationary powerful TX for broadcasting CW VLF frequency,
2. Large stationary TX antenna,
3. Light passive metal detector with max bandwidth 4 or 12Hz.
I have proposed to save transmitter and TX antenna, according patents of Vaino Ronka. Let us examine whether is received signal by some powerful VLF radio station.
Before we begin to design the advanced Okantex System 2, let's review the information for antenna of unit U1, which provide far Okan, and think whether it is reliable.
In the attached figure is shown the most likely circuitry in antenna box. The transistor is connected to tap from tank inductance for antenna matching. Winding L3 is used for fine tuning of the resonant frequency.
Under the circuit are sketched Russian parts that might have been used. Note that the capacitors have metal housings. A capacitor much like the 9V battery, and the other a metal pipe. How should be oriented ferrite cores to emit a magnetic field down to earth?

[okantex]

Hi Mikebg,
for buzzer , owner had used a cannary home outdoor beepers, it is not sophisticated .

and I remember a word of owner as there was a crystal in the coil part.
and there must be a 9v battary at coil part.

[mikebg]

Do not use a conventional AM radio receiver in metal detecting system!
Radio amateurs claimed yet another shortcoming of the conventional AM radio receiver when used for metal detecting
(as in Okantex system).
Every modern receiver for AM (amplitude modulation) has AGC (automatic gain control) with relatively high speed (small
time constant) when signal increases. This is very detrimental to the processing of slowly changing target signal. Since
the demodulated target signal has a spectral composition from DC to 4Hz, the AGC was able to inhibit it significantly,
which means a significant loss of depth.
The time constant of AGC at weakening of the signal is usually greater. For these two reasons, the conventional
receiver can not respond to the weak target signal, but after overtaking the target, it will be a pause in threshold tone.
To avoid suppression of the target signal, we must increase the time constant of AGC for positive transition process.
However, the vintage receiver L006 has not only AGC, but AFC (automatic frequency control). I expect the Russian radio
amateurs to send a description of the AGC and AFC schematics in receiver L006 to consider what should be amended
so, as not to lose the depth of detection.

[mikebg]

The term "2boxxxx"?

What means the term TWO BOX or “2box”?
This kind of metal detector whether or loop configuration in EMI sensor?
The REMI group is training for amateur MD designers, so it has undertaken to rediscover, reinvent, revise and redesign EMI sensor and devices connected to it.
REMI group was founded by amateur radio designers, not familiar with strange English terminology in the field of metal detectors. The group required to define terms and concepts used so far in this area so the designers to understand each other. Note that the term "EMI sensor" is the revised variant of terms: "search coil", "loop", "antenna", etc.
A REMI group member can be considered anyone who rediscover, reinvent, revise and redesign something in EMI sphere what other members don’t know. This can be a term, for example “TWO BOX” or 2boxxxx. Then the reviser should send a description of his work for discussion by the members before it is published.
This is different from writing articles in Wikipedia, because there the authors are anonymous and problems are not discussed. Any other opinion is expressed in Wikipedia by a new version of the article.
The REMI group forced me to act as its spokesman of the paradoxical reasons:
1. I have not learned English. I can deal with English as use Google translating machine only. I know German and Russian, which sometimes helps me to correct machine translation.
2. I hate to speak by QRP amateur radio because of my language problems and since in most cases, the radio correspondent does not hear me or I do not hear or understand him. I designed and built successful TXs, RXs and antennas for QRP ham radio, but other use them.
3. I can change some weird English terms in the fields of electricity, electronics and metal detectors. For example, the term "Electromotive Force" means to me something that should be measured in Newtons. Note that in postings I use abbreviation EMV (electromotive voltage) instead EMF.
Now to put in my place and try to answer the question of a member: „What means TWO BOX metal detector?” He was frisked WEB and Wikipedia and was found that
“Two Box - A metal detector that has the transmit and receive coils mounted in separate housings. By enlarging and separating the transmit ...” www.beginnermetaldetecting.com/metal-detecting-glossary/
Then I read the manual for metal detector GEMINI-3. It is indeed a two box MD.
My next step was to explain the definition:
The TWO BOX metal detector is a system of two boxes TX and RX used by two operators. Each box contains its battery and antenna.
As an illustration of my definition, attached is a sketch made by an radio amateur at the Plovdiv Fair somewhere in 70-ies.
The sketch represents a TWO BOX system produced in 70-ties by a Canadian company “Sharpe Instruments”. The system is used for prospecting with sine induction at 1600Hz.
Both boxes seem more as large hoops and operators seem as coil cores. Both units are connected by a long cable trailed on the ground.
Note that when the system is in action, the mutual inductance between loops varies random.

[mikebg]

REMI redesign

The REMI group decided that the design of Sharpe Instruments has two major disadvantages: coplanar nonbalanced coil configuration and long cable between units trailed on the ground. The group eliminated the shortcomings making orthogonal loop configuration to reduce AIR signal in RX and synchronous demodulation without cable connection with TX. The REMI redesign looks like this:

[mikebg]

Airborn 2box

Experiment shows that the improved design has one flaw inherent in all TWO BOX systems: unstable mutual inductance (variable AIR signal).
CONCLUSION: "2box" or
TWO BOX is an EMI sensing system in which the mutual inductance between RX coil and TX coil changes random when RX and / or TX box moves.
This means that the two loops are not fixed, so RX coil receives changing AIR signal.
However the term TWO BOX is used by merchants of metal detectors and Charles Garrett to denote Orthogonal Coil Configuration. Perhaps this is because the boxes of Gemini can be mounted in a rod as orthogonal coil configuration with induction balance. But the GEMINI system can act as TWO BOX used by two operators. However this is not possible for other “2box” machines as TM808 and TF900, because they are not TWO BOX detectors.
The definition of the REMI group is illustrated in the attached figure. The sketch shows an airborn prospecting system. It is TWO BOX system, because the mutual inductance between RX coil and TX loop changes random during the operation.

[mikebg]

Nonorthogonal or unnamed loop configuration

Carl Moreland uses the correct term “orthogonal” induction balance for “2box” machines as TM808 and TF900. However an EMI sensor type “Depth Multiplier” can be set in induction balance with not orthogonal loops configurations. This is illustrated in the attached figure. Note that the “unnamed” loop configuration is more suitable for “2box” machines because RX loop is moved close and parallel with ground. This is a reinvention because an ancient “Audio Spectrum” metal detector uses the scetched EMI sensor. Unlike the fixed coil configuration in TM808, TF900 and Depth Multiplier of Garrett, the loops can be adjusted to induction balance with fine rotation.

[mikebg]

Modernized variant of an ancient "Audio Spectrum" machine. The TX loop can be adjusted to induction balance in a nonorthogonal "nameless" configuration. Note that the RX loop or twin RX loops are close and parallel with ground unlike a conventional orthogonal configuration.

[aft_72005]

Modernized variant of an ancient "Audio Spectrum" machine. The TX loop can be adjusted to induction balance in a nonorthogonal "nameless" configuration. Note that the RX loop or twin RX loops are close and parallel with ground unlike a conventional orthogonal configuration.

Hi mikebg
Your idea is interesting , are you had practice ?

[mikebg]

AGC and AFC systems in receiver L006

AGC and AFC systems in receiver L006

AGC system operates as follows:
Without signal in input of IF AM amplifier, through diode VD2 flows base current of transistor VT8, which determines operating point of transistors VT8 and VT9. Trimmer R18 is selected voltage delay, at which the AGC amplifier transistor VT5 is closed.
When there is carrier frequency signal in the input of IF AM amplifier, in the output of amplitude detector (on the diode VD2) is formed DC component of voltage. Due to detector current, increases the base current of the transistor VT8, and hence the emitter current of the transistor. The voltage on resistor R18 increases, and transistor VT4 opens. The collector current of transistor flowing through resistors R4, R2, reduces the voltage on the basis transistor VT1, which, in turn, causes an increase in current through transistors VT3 and VT5. Collector circuit of these transistors are fed through a resistor R7, on which increases the voltage drop.
If collector-emitter voltage of transistor VT3 achieves 0,1-0,15 V, then its input resistance decreases sharply and it shunts tank circuits connected in the collector of transistor VT1. This leads not only to reduce the gain, but also to expansion of the bandwidth of the amplifier due to changes in labor quality factor of tank circuits L2, C7, R6, and L1, C6. Capacitors C5, C8 and C10 filter AF and IF components. Voltage of AF signal from the output load R28 emitter follower VT9 through RC filter (R26, C23) and the switch S1 is fed to the input of AF amplifier.

The IF AM signal voltage from collector of transistor VT6 is fed to the input of the discriminator tract AM through resistor R16 and filter R22, C21 . Discriminator is build of transistor VT10 and diodes VD4, VD5. From the output is removed control voltage for the AFC-AM (automatic frequency control for amplitude modulation) and for differential amplifier of indicator P1. The load for transistor VT10 is two tank phase shifting transformer L3, C28 and L4, C32 with inductive-capacitive coupling. (See circuit diagram in posting #519 ).

Control voltage for AFC-AM is supplied to variable-capacitance diode VD1 is located in block SW-MW-LW (A5) through the resistor R45, the switch S1 (contacts 2-3), contact 4 of block A4 and filter R25, C16 of block A5 . Control voltage to the differential amplifier is supplied with indicator midpoint divider R40, R41. Differential amplifier for indicator P1 is build of transistors VT13 and VT15. It provides the arrow indicator P1, which is connected through contacts 12 and 13 of block A4. The differential amplifier operates as follows.
When no input signal to the radio, the transistor VT13 is closed and the transistor VT15 is open and through the turnout indicator P1 proceeds collector current of the transistor. The bias voltage at the base of the transistor VT15 is fed directly from the battery through divider R54-R56. Therefore, the initial deflection of the indicator P1 is set with trimmer resistor R56 so that it corresponded to the nominal voltage of the battery, while at least battery discharge indicator reading decreases.
When there is input signal to the radio, increasing positive voltage at the base of the transistor VT13 and increases its emitter current. The voltage drop on resistor R51 reduces the collector current of transistor VT15, flowing through the meter P1. When the voltage on the base of the transistor VT13 is greatest, which corresponds to fine-tuning the received signal, the current through the meter P1 turnout will be minimal and thus deflection of the indicator will also be minimal.

[Esteban]

Mikebg: Most information wanted about all system Timbre 1898. And other old papers you have. If you accept, please, send me to

[email protected]

[mikebg]

To aft

Hi aft,
Your question gives rise to two answers:
1. This not an idea. This is a rediscovery. Metal detector with such a configuration of coils was established more than 100 years ago. It was made from wood with no metal and plastic pipes. It worked two operators. The first one wore headphones and the sensor similar to that shown in the upper figure. The second operator is wearing a heavy box, which had a battery and electric motor to power rotating interrupter for TX coil.
2. I practice about two years as a seeker of meteorites. Two years ago, I modified a device for demining to detect stones stuck in the dust. This machine called my friends "ShingleFinder". So far I found two small meteorites gaunt corroded by corrosion after I dug up more than a thousand stones. My dream is to find meteorites beautiful and expensive to sell it to collectors, jewelers and scientific institutes.
My hobby was design of TXs, RXs and antennas for QRP amateur radio. One group of people with my hobby (called REMI group), chastised me over two years to act as spokesperson for its work in the field of metal detectors. The reasons for this punishment and I have several of them pointed out this forum. What means the abbreviation REMI, also explained to the Forum. During this year my sentence ends and then the author of my posts in the forum will be just me, without editorial interference from others.
But I am not only a spokesman for the group, but reinventor as all its members. My great merit last year is that I rediscovered in a patent the principle for deepest metal detection. The real inventor is Vaino Ronka. During this year, the REMI group will design and made a family of models using this principle, which will be called GLEANER. Now I have for translation in English drafts for postings about circuit diagrams of TX, RX front end, form for coil winder etc.
In that year, the group will make the forum very interesting because are ready revised circuit diagrams for experimening.

[mikebg]

To Esteban

Esteban, the REMI group has 3 ancient circuits only. I have posted 2 of them because the difference of third one #1902 is in TX and headphones only, but the action of its TX is unsolvable for us. The circuit diagram of strange TX 1902 seems so: