Post photo of your LRL project?

[Fred]

Hi Esteban,

No mystery here, no ovnis, no vampires, there is people wich wish extend this theme to legend field! Esteban

thanks for explanations,but you understand that we have been talking about LRL for so long without any evidence of working or scientific background, that it seem logical we associate it to legends

But for to know all this you must go to inland in relic sites, no dictate from a chair and a computer.Esteban

I agree with that : this is the problem with internet. too much studies that raise more and more questions,and no time left for experiences....

Regards

Fred.

[Max]

No mystery here, no ovnis, no vampires, there is people wich wish extend this theme to legend field!


You catch this small difference in the audio out of the IC, but you can't ear normally. So the simple beeper do the job.

Any simple audio amp. can do the job, but in this case you can't achieve much distance.

Semiconductors base is ready for to accept electrons, these semiconductor has noise causes by termal movement of atoms. The field of the good conductive metal buried for long time affect the vecinity of the electrons in the semiconductor, and produces a small microvolts, very easy to undrstood this.

So a antenna system connected to this input and adjust the system at the best point of sensibility, out of false beeping, is OK for to do the job.

In other words, also you don't need RF part, yes audio, but RF is more sensitive, and as I use here receiver part, I call this passive device, this is in my terminology regarding electronic LRL. Other thing is a system based in transmitter/receiver, so I can name this as active device. Also radio transmitter/receiver or metal detector (IB, BFO, resonance-off, etc.) is active for me.

All depend of your imagination in electronic LRL systems, never ends ideas in this field.

But for to know all this you must go to inland in relic sites, no dictate from a chair and a computer.

Regards

Esteban

Hi,
can I make some guesses and questions ?

You add a turn to the tuned circuit , right ?

That way you lower the frequency of tuned circuit from the standard 88-108 MHz FM band of receiver to something less... say 60-80MHz... ok.

But then you wire a cap from omnidirectional antenna to the volume pot... of radio and parallel it with another used for external sensitivity settings.

OK... if so... I suppose then your beep generator is something threshold detector that drives a 555 timer and give pulses to the buzzer... maybe a selfoscillating one like the sonalarme we talked about.

Ok: if there's a reduction of signal strenght at antenna at the tuned frequency , and if there's no agc control on the radio active, you'll get lower volume ... so can trigger the audio generator.

The second option is a tuned circuit after antenna and before the circuit... passband filter for the radio input...maybe tuned to a particular frequency.

All seems have a meaning till now but then...

the questions are:

1. what causes the signal strenght reduction ?
2. what's the frequency of tuned circuit and why if any particular frequency instead of others ?
3. is there some broadcast or other kind emission at that frequency that superimpose with the supposed "useful" signal ?

Kind regards,
Max

[Esteban]

"You add a turn to the tuned circuit , right ?"

No, quite a turn. You can add or quite a turn, the theme is go some far of FM band.

"Ok: if there's a reduction of signal strenght at antenna at the tuned frequency , and if there's no agc control on the radio active, you'll get lower volume ... so can trigger the audio generator."

The necessary volume for to made stable and very sensitive.

"1. what causes the signal strenght reduction ?"

Maybe is associated for long time buried conductive metals. Also I'm not sure all phenomenons implicates, is complex.

A man was asked how he found a treasure in the 60's, a poor man, how he can detect the gold. And he tell with a Philips radio 6 big X 1.5 V batteries in AM. He told that over the treasure the radio was detuned! You can do this: tune a AM station and put near the ferrite a coin. What's happen?

"2. what's the frequency of tuned circuit and why if any particular frequency instead of others ?"

As you see, is for study. I remember that I connect the system antenna-small coil-variable cap. in input RF of TV and manage the tuning great, so directly can be useful for to filter undesirable frequencies.

"3. is there some broadcast or other kind emission at that frequency that superimpose with the supposed "useful" signal ?"

This is possible since this experiment: you tune near a station in FM band and positioned the small spiral coils (see drawn), move only one of them and leave the other fix. You will note that improve the reception. So detune a little the tandem. Buried metals tend to complete the tunning, so can be useful another kind of emission, but to depend of radio station is very problematic.

As Fred said, no scientific background we can found regarding long range metal detection. This FM system is for short range, maybe few meters, no more than 3 or 5 for a coin.

This job is very empiric, tons of experiments you must do... And you discover this, regarding electronic LRL: almost ALL SYSTEM you have in mind works in different grade. So the phenomenon is complex and you never are sure if electric, ionic, magnetic, but I believe is a combination.

[Qiaozhi]

This is possible since this experiment: you tune near a station in FM band and positioned the small spiral coils (see drawn), move only one of them and leave the other fix. You will note that improve the reception. So detune a little the tandem. Buried metals tend to complete the tunning, so can be useful another kind of emission, but to depend of radio station is very problematic.

What do you mean by small spiral coils?
Are these air-cored, wound on ferrite, flat .... or what?

[J_Player]

What do you mean by small spiral coils?
Are these air-cored, wound on ferrite, flat .... or what?

My guess is flat air core spirals attached to plastic disks with hot melt glue.

Best wishes,
J_P

[Esteban]

My guess is flat air core spirals attached to plastic disks with hot melt glue.

Best wishes,
J_P

Yes, is right! Just few turns.

Regards

Esteban

[roberts]

"..A man was asked how he found a treasure in the 60's, a poor man, how he can detect the gold. And he tell with a Philips radio 6 big X 1.5 V batteries in AM. He told that over the treasure the radio was detuned! You can do this: tune a AM station and put near the ferrite a coin. What's happen?..."

This is a classical thesis substitution, usually met in lightly conversations.
If you want my opinion on this; i will say (generally) YES, radio will be slitly detuned off main frequency, in AM band if you put some ferrite rod or descent piece of metal near oscillator. Yes.
But, NO if you pass with radio over simillar piece of metal on larger distance than 1-2cm. Any kind of metal. NO. Radio will stay tuned hard as a rock.
So i can pull some conclusion from this; either that man founded tons of burried treasure, at shallow depth, and even than only if he passed with radio few centimeters away from it.
Knowing this it is logical to say this method is uselles in metal detecting, cose you have to put your apparatus very close to desirable item.It is not long range locating any more - it is shortest possible range locating than.

You said 3-4 meters. I said WOW! Forget 40 meters, even those 3-4 meters would be fantastic result! I dream about device with which i can detect coin at 3 meters depth or distance!
Seems that you didnt understood my point from earlier posts;
coin is to small and lite, it can not disturb any kind of radio reception on such long distances like 3-4 meters. Conditionally it can disturb reception only if you close it to device's oscillator at 2-3mm distance..or even less.
No way.
My life occupation is radio. I work and live radio. Aint no coins arround disturbed any reception so far.Aint no larger metal items too.
Various propagations are only source of disturbances in reception. Take term propagations generally, including million various causes. But all those causes are global, not so minor and local as tiny,small coin.
No matter how you mod that radio.
I will return to Zahori again. Zahori (although trivial device) is most sensitive
specimen from that undefined group of so called lrl devices. If you want to follow and scope all static changes surrounding us, you just make it, add stronger audio (ivconic's mod) and enjoy!
But those changes you hear with your device are certainly not caused by single coin. Trust me. Even if you ocassionaly find a coin or two, walking arround with your device, it is not cose your device is functional, but cose terrains at your home are pretty full with coins. You better take some proper VLF/IB and start "cleaning" those, before somebody else do that.
About my field experiencess....i am experienced enough. Prospecting is my hobby for over the 20 years. Maybe not great as somebody's else, but descent enough to make me conversant to talk about things here.
By strange and funny coincidence, radio is my life. I do understand most of things related to radio very good. So anything you posted here, relating to radio is properly checked so many times before. You better trust me about it, it is in your interest more than in my.
You better do some extra experiments with that device, than come again here and inform us.

[J_Player]

I will return to Zahori again. Zahori (although trivial device) is most sensitive specimen from that undefined group of so called lrl devices. If you want to follow and scope all static changes surrounding us, you just make it, add stronger audio (ivconic's mod) and enjoy!

Hi Robert,
Most of Esteban's pistol style LRLs have been built with coil transmitters and receivers. From what I understand, at low frequencies (less than 200 khz) these coil antennas are better suited to receiving radio waves than an antenna designed to receive the electric field. because of better electrical noise immunity. After reading many of Esteban's posts about LRL detection from looking at received signals showing a phase shift, I think he believes a coil antenna is much better for locating treasure. I think he is trying to measure changes in the transmitted radio wave in the vicinity of the target without picking up stray man-made electrical static and noise.

I don't believe any electric field or magnetic loop antenna can detect a coin at long distance of more than a few feet. But maybe it is possible a loop antenna can respond to a halo caused by long time buried metal. Little is known about a halo, except it has been proven that there is a column of metal ions that rise through the ground at the location of the long time buried metal. There may also be electrical and chemical properties that allow a VLF radio wave to react to the presence of this halo. Nobody has proven whether a halo exists or whether radio waves can be altered by the presence of a halo. We only have the reports of Esteban and Morgan who say their coil type detectors responded to long-time buried metals.

Now my question to you is this:
1. First, am I correct that a loop antenna will be more immune to electrical noise from buildings and man-made electrical devices, and best for receiving directional VLF signals?

2. If a coil method is better for receiving VLF signals, then what would be a good design to monitor reliably some very small phase shifts in a received signal? Is there a better way than Esteban described using audio demodulation?

I don't claim the halo effect is able to make changes in transmitted or received radio signals, but I am interested to know the best method to construct a portable loop transmitter/receiver to make a real test of Esteban's claims. Are you able to design a TX/RX apparatus that will do this better than Esteban's apparatus?

Best wishes,
J_P

[roberts]

I really cant imagine other way except choosing loop.
Audio demodulation is easiest approach. Lets adopt it for a start. Certainly not best here, but easiest. I cant involve much of my time here due other jobs, and cose this will be pretty trivial task, so...ok...lets adopt audio demodulation.
Ok. If we take 200kHz as desired frequency, conversion to wave length will give us:
1499.62 meters, lets say 1500m.
But let's rethink this frequency. I dont like it. Much less effrot for me later, if we use
455kHz as desired. Why? Since i consider this as pretty trivial job, i would like to make
my life easier later when designing project for you here.
So let it be 455kHz. Right?

455kHz will be 658.9 meters wave lenght. Let's say 659m. Further W/2=329m and W/4=165m.
So now we do know possible lenghts of desired wire antena.
Now.... which type of loop antena should we use here? Directly coupled loop or indirectly
coupled loop? Directly coupled loop has directly connected its windings to amplifier.
To achieve electrical balancing, main tank coil (loop primary) must be center tapped to
ground.Indirectly coupled loop will require transformer coupling - meaning link of windings
to couple received signal to the receiver.
Here we do not want just to pick up any signal. Here we desire to receive signal and if
possible (it is) to approximately distinguish signal direction, so we can later folow it
and eventually find its source. Right?
Therefore if we choose directly coupled loop in our design, that loop must be critically
balanced! Now pay attention on this! Any differnce in windings left or right from center
tap will hardly disturb loop balance and eventual direction finding will be unaccurate!
But totally unaccurate! Why? Because we do not want here to catch some strong TX, but very
weak (if there is any) signal produced from changes caused by presence of metal in its
vicinity. We are talking here about very,very weak signals! Hard task, if not impossible!
So loop design would be most critical here. That's why i do have
so much doubts in Esteban design and its accuracy. Among other doubts. Ha,ha,hah!
Now, knowing this i would rather choose indirectly coupled loop for my design, cose it is
much easier to balance.It must be air core loop (as it is here).But there is catch too, here.
This setup will pick up more interferences, static changes etc. If it was fixed to only
one postition - less problem. But walking arround with it, changing positions will cause
distorted reception, noisy signal etc.
There is a sort of "thumb rule" here also; the larger loop is better in sensitivity than
smaller one. So...i really cant imagine what Esteban expect to achieve here with small, handy
portable loop he made!?
So i will rather "wash my hands" off designing loop here. I will let you to design proper
loop for this. I can only design receiving circuitry for it.
So if you accept this term, we can start.
I will stand infront my design as 455kHz receiver and you must stand infront loop for that
design. All right?
So i suggested 455kHz frequency. You need loop to cover 659m wave lenght. you may choose
between w,w/2 or w/4. I will rather suggest you w/2 in this special purpose. I think it
is probably optimum compromise between benefits and losts.
So if you have will to start say it, i am waiting.
I will need to see your loop choise ready here, so later to design rx circuitry according it.
Deal..?

[Esteban]

So, for to make a coil at 10 Khz you need 29,984.5 meters of wire or 29.98 km. This is impractical for metal detector. At 1/2 wavelenght = 14,992.25 o 14.9 km and for 1/4 = 7,496.125 km...

For the same reason, for to receive radio or emit radio waves you don't need kilometric antennas!!! A think is wavelenght and other is to tune a simple coil (tank) at desirable frequency.

And don't forgett the inherent frequency of each metal, atomic vibration, a very precisse frequency for each metal.

Of course, radio no detune easyli in presence of metal, but the small change in the background noise is a simple explanation.

No accurate at all this simple system, really no good distance, just is an example.


Regards

Esteban

[Dell Winders]

http://www.borderlands.com/newstuff/research/ground-ant.htm

[roberts]

So, for to make a coil at 10 Khz you need 29,984.5 meters of wire or 29.98 km. This is impractical for metal detector. At 1/2 wavelenght = 14,992.25 o 14.9 km and for 1/4 = 7,496.125 km...

For the same reason, for to receive radio or emit radio waves you don't need kilometric antennas!!! A think is wavelenght and other is to tune a simple coil (tank) at desirable frequency.

And don't forgett the inherent frequency of each metal, atomic vibration, a very precisse frequency for each metal.

Of course, radio no detune easyli in presence of metal, but the small change in the background noise is a simple explanation.

No accurate at all this simple system, really no good distance, just is an example.


Regards

Esteban

No Esteban, you mixed up things here. Conventional VLF-I/B at 10kHz working frequency doesnt really work as radio transmitter.No, not at all. Coil is used to generate electro magnetic field with certain flux. Radio waves produced that way are not our concern. You may say those are colateral in whole process. Any metal in coil vicinity, exposed to generated em field is also producing alternating em field, later picked up with rx part of coil.
Coil balance is disturbed, phase of tx signal is shifted, man have more than enough elements according to whose can distinguish metal preferences than.

But concerning LRL you talked about,situation is quite different. You cant rely on em field and its flux any more. You are talking about LONG range locating.Also you want to use radio waves, real radio waves.
In this case you must think about proper antena-loop in this case.
Among other reasons, loop preferences are also to be taken cared carefully. That's why is not practical to design device for low frequencies...10kHz for example, loop it self would be "heavy weight", imposible to carry!
That's why i picked up 455kHz, easier to make loop for it.


"And don't forgett the inherent frequency of each metal, atomic vibration, a very precisse frequency for each metal."

I do not know neither one metal frequency. For real. Those "frequencies" man can meet in various lrl articles are all false. I think aint no metal producing any frequency.
If it was, than it will be possible to measure those. Since it is not possible to measure those - they dont exist.
Or any other method to prove any metal frequency.Plain piece of metal.

[roberts]

Dell it is very interesting article. I will read it later.
Regards

[J_Player]

I will need to see your loop choise ready here, so later to design rx circuitry according it.
Deal..?

I don't know how to design a loop. This is the reason I asked you. The loop transmitting antennas I have seen in this forum are generally similar to metal detector coils with the Faraday shield removed. I doubt any radio engineering went into these coil transmitters, but they have been experimented with for a long time to find the best operation through trial and error.

While I don't know how to properly design a transmitting loop antenna or receiver, I do know some basic parameters that the system should maintain:

Since this is a field unit, the entire transmitter and receiver must be lightweight and portable, and should run on battery power for at least 4 hours operation before the batteries are discharged. The largest coil should not be more than 30 cm diameter. The preferred frequency is between 40 KHz and 160 kHz because this is a range that has shown the best stray noise immunity for this application in actual field testing. But 455 KHz will also work if necessary.

I believe the idea is to transmit a modulated carrier with the transmitting coil, then try to detect minute fluctuations in the received demodulated signal. The fluctuations may be seen as phase shifting or amplitude fluctuations, and maybe other very small artifacts in the received demodulated audio square wave. In this kind of transmitter and receiver, the receiving coil is carefully fixed in a position where there is no magnetic coupling to the transmitting coil. The only received signal should be an RF signal that is returned from the transmitting coil by reflection or other methods.

The received signal can be compared to the transmitted signal in order to find fluctuations. The receiver could also be watching for changes over adjustable time constants to find phase shifts or other irregularities in the signal. I suppose there are many methods to find fluctuations, and I don't know which is best.

I believe the transmitter is not so critical as long as the frequency and the power transmitted remain constant. I would think less than a watt is adequate for testing purposes. The receiver is the critical part. It must discern minute fluctuations in the signal, and must also be directional enough to find the source of the fluctuations.

I don't mind building the coils and transmitter and receiver, but I really don't know how to do it with any expertise. The only thing I know about this is any apparatus should be built without any metal parts near the coils, especially iron. If you can give some instructions of how to construct the device, then I can start making the coils. What I need to start is the wire size, and lengths, how many turns, and what kind of insulation. After the coils are ready, then we can start building the circuitry.

Best wishes,
J_P

[Esteban]

The preferred frequency is between 40 KHz and 160 kHz because this is a range that has shown the best stray noise immunity for this application in actual field testing. But 455 KHz will also work if necessary.

Best wishes,
J_P

Low changes you'll obtain at 40 Khz, I try 59.5 because I made a coil center tapped and oscillator. The coil resonate at this frequency with the capacitors I have adjusted at the pF range. Is good, but changes is slow. Found with it a gold button Navy and mark of glasses plated in gold.

At 300 Khz, the detector tend to detect also metalic paper of cigarette box and other "trash". I believe 160 Khz is good. Also Alonso told me this is a good frequency. See the BFO I posted in this thread, frequency is 138-140 kHz.