BLACK HOLE ANTENNA

[mikebg]

Can mikebg please elaborate on thread post 24, I have just completed my first Houndog and would like detailed drawings of his expanded sense area / target design.

MotoLupe, you should build a sensing head having DOD loop configuration. It is suitable not only for regenerative circuit like HOUNDOG, but also for narrow band (VLF) and wide band (PI) metal detectors. I'm using it in a VLF detector with operating frequency 20 kHz to locate small meteorites.
http://www.geotech1.com/forums/showp...00&postcount=6
http://www.geotech1.com/forums/showp...8&postcount=21

Here are improvements of HOUNDOG circuit:
http://www.geotech1.com/forums/showp...90&postcount=8
http://www.geotech1.com/forums/showp...3&postcount=54
The LM386 operates in these improvements with increased gain.

A LM386 with increased gain can be used as preamp in other types metal detectors, for example in PI MDs operating in frequency spectrum from 2kHz to 20kHz:
http://www.geotech1.com/forums/showp...67&postcount=2
http://www.geotech1.com/forums/showp...54&postcount=2

[MotoLupe]

Post 24 of Back Hole Antenna Details

Can mikebg please elaborate on thread post 24, I have just completed my first Houndog and would like detailed drawings of his expanded sense area / target design.

[mikebg]

The joke is that there no joke:-). However there is an error made of NASA experts when they simulate by SPICE a wrong circuit diagram of Q-multiplier.
The wrong circuit diagram is given in posting #3. This is not a Q-multiplier because output can not pump energy (current) in tank circuit.

[DOOLEY]

nasa joke

good point i was waiting for that explanation aswell.

[Tepco]

And what happened to 1st April NASA joke then? US 5296866 are issued. (John F. Sutton, mar.22, 1994)

[mikebg]

Barnaby is the text extracted from EVERYDAY PRACTICAL ELECTRONICS Noviembre 2004 (the author's original text Thomas Scarborough).

Maikl, I also knew that. In February I made up a pdf file with the masterpieces of the Revd Thomas and his picture of the pulpit:
http://www.geotech1.com/forums/attac...3&d=1265407197

You ought not so quick to issue what is the true author.
I was hoping to catch some of the line and challenged the above quote attributed by me to Barnaby Brown because he is not so great reputation.

[maikl]

Barnaby is the text extracted from EVERYDAY PRACTICAL ELECTRONICS Noviembre 2004 (the author's original text Thomas Scarborough).

[mikebg]

To participants in this forum:
1. Look at posting #8 and see Fig. 7A and Fig. 7B to understand the difference between Armstrong and Meißner oscillators. They use only one tuned circuit.
2. See Fig. 8 and compare with sound oscillator in posting #16. The principle is similar: Piezo Sounder X2 operates as transmitter or loudspeaker . The piezo sounder X1 is receiver or microphone. Now see the circuit diagram in posting #10. This a better operating circuit because TX coil is driven with large current. The CMOS ICs can not deliver so strong current as an audio frequency amplifier LM386. It can operate with 8 ohm and even with 4 ohm load.
3. All oscillator circuits in posting #8 have TX and RX coil, however some circuits (Colpitts, Hartley) use MONOCOIL (self-inductance). This is the worst type sensor for for metal detecting because coefficient of couplig is unity (AIR signal is maximum). See the sound generators (oscillators) in Fig. 1 and Fig. 2. They operate with equal principle with circuit in posting #16: transmitter (loudspeker) radiates noise. "An amplifier can oscillate, but an oscillator can amplify". This saying is from era of regen radio. Each oscillator can operate because amplifies noise.
4. Now read what writes Barnaby Brown, the author of circuit diagram in posting #17:
http://www.techbites.com/20090807346...w-seekers.html
"Circuit Details:
In Fig.1, the TCO transformer is replaced by two search coils, L1 and L2. These have the
same action as the transformer in a TCO, L1 being the “transmitter”, and L2 the “receiver”. On the
basis of its similarity with a TCO, the author has named this metal detector a Coil Coupled
Operation (CCO) Metal Detector."
CONCLUSION: We should use a powerful IC for search oscillator.

[Krzysztof]

Hi Maikl.
Supports everything that was in the # 19.
Although the mix-fifth harmonic generator with a generator and the BFO is increased sensitivity range.
But at this frequency is detect any movement of the hand, head and your every step will affect the signal.
The tone here is a treasure chest forget, no, unless this box is a crash to the ground.
No matter how this system is called, then there is no Tx / Rx. There are only a coupling coil generator "Maisner" a large surface area, then R2 is completely OK.
How do you want to find something, then choose another MD.
Piece of paper with ideas of Reverend Thomas put it in the trash, not cursing sin, as once again look at the real bible and remember your nerves.
Maikbg great translator, but he now speaks quite a different layout.
MW range of support for listening to the radio, and to select a lower frequency of MD.
GPR system as it would be too easy.
Read the story RADIO 1930 years, there have been such a coil on the MW and the same generator.
He worked under the excitation point, and it was not possible to move that radio station did not run away.
Even then, radio was such a detector, although they did not know 4969th
Best regards Chris.

[mikebg]

Hi mikebg. I'll try this combination (unfortunately only in winter when I had a surplus of free time). But I will keep the voltage of 12V for TL071 and I will tell the results. HC04 does not have and the combination I do not try. L1=100ohm (and what is the inductance which is more important?)

Maikl, because of high operating frequency, the circuit in posting # 17 is very sensitive for targets at air test. The reference oscillator (BFO) in that circuit generates too high frequency. Despite C2 and C3 appear in series, equivalent tank capacitance is not 11pF but more because of stray capacitances. For calculation of oscillating frequency I use equivalent capacitance 20pF. With inductance L3=100uH, it gives oscillating frequency above MW band. That means your search oscillator also oscillates at MW frequencies where the earth generates large GND signal.

To test search oscillator circuits with CMOS IC , I used my sensing head designed for IC type LM386 (because it can deliver much more current for TX coil). My circuit is like HOUNDOG, but RX coil is also tuned. I tune RX and TX tanks to frequencies below 20kHz to reduce GND signal. For addional suppressing of GND signal, my sensing head contains two RX coils (about 30mH and 56 ohm each). They are connected in series as TWIN LOOP configuration shown below. Since both RX coils are coplanar and connected in opposite direction as shown in right scheme, total inductance increases to 63mH (mutual inductance appears positive). The rectangle TX coil is placed in the center of head (in middle between RX coils) and each RX coil is placed almost in induction balance with TX coil. Despite for testing with CMOS IC I used smaller capacitances, oscillating frequency was no more than 30 kHz. The TX tank of HOUNDOG is also tuned to VLF frequencies. Because of lower operating frequency, my circuit has no more sensitivity at air test as the circuit in posting #17, but I'm sure it operates better in the field with conductive soil.

[maikl]

Hi Maikl.
I am for reliable knowledge represented someone about modest possibilities, who they would execute this wonder here how in previous # 17, he did not send to all devils Thomas' reverend. This usual arrangement BFO.
This is normal generator Meisner, coils serve to coupling manageable and not no Tx / Rx.
The generator of reference will act with dependence from resistance of coil, it can lacks the small of condenser here? 1Mom has to make amplifier from comparator, and to does not reduce kindness Q.
The very critical setting to op the point of work of generator, lack of tensions of reference - the amp; TL07 will act worse and worse with growth of frequency of work.
About influence of temperature better does not remember.
Conclusion: the user will hear every grass and the lump of the ground, but not the signal of treasure!
It such CCO / BFO made on SN7400 arrangements and was could meet in popular periodicals for 1975 year SN7474. I am for return of Thomas' reverend to original bible.
Best regards Chris.
I enclose patern inwerter 4069.

Hi Krzysztof. For this circuit is very important to be well done Faraday protection (coils and cable and coils) because it works at high frequency search oscillator IC1a oscillates at around 500kHz, a second oscillator, IC1b, together with buffer IC1c, serves as a beat frequency oscillator,
oscillating at around 2·7MHz. The entire circuit should not be set to maximum sensitivity, as it will then react and when you wave the hand over the coils.

[maikl]

Maikl, you know that for me this circuit is incompetent design.
Resistor R2 is top of incompetency. It reduces TX current and draws useless DC current 3mA. This can be easy improved by a capacitor C5 to stop DC. The TX current can be increased by connecting not used gates IC1d, IC1e and IC1f in parallel to IC1a . Capacitor C4 should be electrolytic and circuit will operate with 9V battery. Try this and measure operating point in pin 2. Voltage measured with DC voltmeter should be almost half of battery voltage.

Hi mikebg. I'll try this combination (unfortunately only in winter when I had a surplus of free time). But I will keep the voltage of 12V for TL071 and I will tell the results. HC04 does not have and the combination I do not try. L1=100ohm (and what is the inductance which is more important?)

[mikebg]

HC04 instead 4069

A better circuit for CMOS search oscillator.
Instead 4069 is used HC04. Instead 12V battery are used 2 x AA cells. To increase TX curent and to lower input impedance of amplifier, the six inverters are connected in parallel.
An inverter of 4069 can deliver output current only 0.9mA. It has low gain because cosists of one stage.
An inverter of HC04 can deliver output current almost 5mA. It has high gain because consists of three stages as shown below.

[Krzysztof]

Hi
Ops! my translating lasted long, different statement was already.
Chris.

[Krzysztof]

Hi Maikl.
I am for reliable knowledge represented someone about modest possibilities, who they would execute this wonder here how in previous # 17, he did not send to all devils Thomas' reverend. This usual arrangement BFO.
This is normal generator Meisner, coils serve to coupling manageable and not no Tx / Rx.
The generator of reference will act with dependence from resistance of coil, it can lacks the small of condenser here? 1Mom has to make amplifier from comparator, and to does not reduce kindness Q.
The very critical setting to op the point of work of generator, lack of tensions of reference - the amp; TL07 will act worse and worse with growth of frequency of work.
About influence of temperature better does not remember.
Conclusion: the user will hear every grass and the lump of the ground, but not the signal of treasure!
It such CCO / BFO made on SN7400 arrangements and was could meet in popular periodicals for 1975 year SN7474. I am for return of Thomas' reverend to original bible.
Best regards Chris.
I enclose patern inwerter 4069.