TESORO GOLDEN SABRE

[Aziz]

The 64 Fold Power Myth V2.0

Hi all,

I thought, we know it better now!!!
WTF, ........
....... <cencored by ACTA> ........
<to open and read the message, STOP ACTA!>


We know, that the 64 fold power factor for doubling the detection distance applies in the far field distance region (distance >> coil radius R).
For distance regions around R and below, the required power factor for doubling the detection distance is less than the 64 fold.

When I want to double the detection distance from distance R to 2R (note R=coil radius), I only need 15.6 fold more transmit power.
For 2R -> 4R = 39 fold more transmit power.
For 0.5R -> R = 4.1 fold more transmit power.
For R/4 -> R/2 only 1.6 fold more transmit power.

You are encouraged to increase the coil size and push the transmit power to the ultimate levels.

Beam me up Scotty!

Aziz

[golfnut]

There may be some milage in doing some traditionally analogue stuff in dsp.

At the output of the detector, there could be a benefit in having quite a narow filter here.

If an analogue narrow band analogue filter was implemented its phase response or time to respond and pass signals thru could make them impractical. A FIR or IIR dsp filter would be a good bet here, as the bandwidth, roll off, phase response or time to respond (group delay) would be superb.

It would more likely mean a a new top down design, not something I am good at (dsp)

Steve

[der_fisherman]

Hi all,

I thought, we know it better now!!!
WTF, ........
....... <cencored by ACTA> ........
<to open and read the message, STOP ACTA!>


We know, that the 64 fold power factor for doubling the detection distance applies in the far field distance region (distance >> coil radius R).
For distance regions around R and below, the required power factor for doubling the detection distance is less than the 64 fold.

When I want to double the detection distance from distance R to 2R (note R=coil radius), I only need 15.6 fold more transmit power.
For 2R -> 4R = 39 fold more transmit power.
For 0.5R -> R = 4.1 fold more transmit power.
For R/4 -> R/2 only 1.6 fold more transmit power.

You are encouraged to increase the coil size and push the transmit power to the ultimate levels.

Beam me up Scotty!

Aziz

I think those thoughts are valid for when the Rx is in a final form. To double the detection range you need a 64 fold increase in power.
But if you have a BETTER Rx, assuming the same Tx, you could effectively increase range over a simpler Rx.
If we assume for a moment (maybe incorrectly) that it is a "radio" type of signal, then we all know that a better receiver can receive weaker stations and improve the sound quality as well.
Is that not basically what is being proposed?
I am interested in learning more....its certainly very interesting and maybe we can achieve something.
So:-
WATCH THIS SPACE!
Regards
Andy
PS. You post came over as very rude as well......if you don't have any belief or want to know more, there are plenty of other great places to be......even on Geotech!! You may be correct in the end, but I personally (and a few others here) want to learn more, just in case......you certainly won't scare me off and I bet I am not alone either, (assuming that was your intention!! Was it?)

[Aziz]

I think those thoughts are valid for when the Rx is in a final form. To double the detection range you need a 64 fold increase in power.
But if you have a BETTER Rx, assuming the same Tx, you could effectively increase range over a simpler Rx.
If we assume for a moment (maybe incorrectly) that it is a "radio" type of signal, then we all know that a better receiver can receive weaker stations and improve the sound quality as well.
Is that not basically what is being proposed?
I am interested in learning more....its certainly very interesting and maybe we can achieve something.
So:-
WATCH THIS SPACE!
Regards
Andy
PS. You post came over as very rude as well......if you don't have any belief or want to know more, there are plenty of other great places to be......even on Geotech!! You may be correct in the end, but I personally (and a few others here) want to learn more, just in case......you certainly won't scare me off and I bet I am not alone either, (assuming that was your intention!! Was it?)

Hi Andy,

schade, ich würde ja gerne mal in Deutsch antworten but many of the peoples wouldn't understand me.

We are detecting only the magnetic property and not EM waves. EM waves can propagate (travel) far, very far. Our coils are shielded and hence we aren't sensing electric fields (shielding blocks EM waves). We are sensing the magnetic field (changes). And we are emitting magnetic fields. We cannot emit EM waves (totally inefficient antenna and due to shielding).

Well, we have talked the 64 fold myth to death in the past. There must be some comments here at geotech.

Cheers,
Aziz

PS: Impoliteness not intended.

[simonbaker]

There may be some milage in doing some traditionally analogue stuff in dsp.

At the output of the detector, there could be a benefit in having quite a narow filter here.

If an analogue narrow band analogue filter was implemented its phase response or time to respond and pass signals thru could make them impractical. A FIR or IIR dsp filter would be a good bet here, as the bandwidth, roll off, phase response or time to respond (group delay) would be superb.

It would more likely mean a a new top down design, not something I am good at (dsp)

Steve

Good point, digital processing can be used to make some idealized filters that can be useful. I assume DSPs are handy for that, although we can do it also in a fast uProcessor. One type of useful filter is a bandpass with linear phase/frequency characteristic, giving a pure time delay with no wave shape distortion; could help keep the target pulse "fat" in the amplification section.

-SB

[der_fisherman]

To DSP or not to DSP

Hi Andy,
schade, ich würde ja gerne mal in Deutsch antworten but many of the peoples wouldn't understand me.
We are detecting only the magnetic property and not EM waves. EM waves can propagate (travel) far, very far. Our coils are shielded and hence we aren't sensing electric fields (shielding blocks EM waves). We are sensing the magnetic field (changes). And we are emitting magnetic fields. We cannot emit EM waves (totally inefficient antenna and due to shielding).
Well, we have talked the 64 fold myth to death in the past. There must be some comments here at geotech.
Cheers,
Aziz
PS: Impoliteness not intended.

I thank you for your answer and apology.

I do understand the 64 analogy with regards to a set Rx electronic and Rx coil.....I am sure its true, or better said, I accept it as being true.

But surely a better receiver electronic and/or Rx Coil (no matter what types of waves or energy we are receiving, though I must say that I would love to understand this technology better if possible), must give a better reception.

I know from personal experience that having a bad Rx system/setup reduces the distance at which I can detect metal. Simple fact!!

So the converse must also be true.....(I know that I am not alone here with such experiences either, c'mon Guys, put your hands up!!!)

Whether or not DSP is the way to go I cannot say, its well outside of my knowledge area, but I very happy to learn more from the experts here. Anything and everything is still VERY interesting....

I am also sure that if spacecraft signals from millions of miles away can be recovered from the very noisy deep space using DSP techniques, I am sure that we can do something to improve a metal detector working only over 40 cms or so!!! Hopefully with "lighter" bits and pieces than NASA needs!!!

regards
Andy

[simonbaker]

Hi Andy,

schade, ich würde ja gerne mal in Deutsch antworten but many of the peoples wouldn't understand me.

We are detecting only the magnetic property and not EM waves. EM waves can propagate (travel) far, very far. Our coils are shielded and hence we aren't sensing electric fields (shielding blocks EM waves). We are sensing the magnetic field (changes). And we are emitting magnetic fields. We cannot emit EM waves (totally inefficient antenna and due to shielding).

Well, we have talked the 64 fold myth to death in the past. There must be some comments here at geotech.

Cheers,
Aziz

PS: Impoliteness not intended.

Doesn't Maxwell's equations say anytime you have a changing magnetic field you also must have an electric field associated with it? Can't block one only.

However, shields are probably effective at blocking slowly changing electric fields more effectively than slowly changing magnetic fields. Now, if your shield was a super-conductor, it would probably block the magnetic fields effectively also.

Oh well...

[Davor]

Actually shields are blocking E field pickup only (say, arcing, static etc.) and could be omitted entirely if symmetric (fully differential) operation is practical. There are "frame" ham radio antennas that also use shielding, and mostly because most of the noise is coupled from near environment via E field. These antennas have maximum in radial direction - remember, radio waves are formed orthogonal to each field. There is not much risk of picking up VLF transmissions with MD coils in the air either, because E field component that it would pick must be horizontal, and all such transmitters emit vertical E. The only way you could pick some transmission is by coupling with something in the ground, and there is no way shielding will help at all.

In short, MD's do their best in pouring as much energy in axial direction to metallic objects underground by magnetic coupling. Not waves. Waves form much, much ( ... much ... much...) farther.

[Ropcsika]

Please help me! I build TGS. If you connect the tx coil it beeps continuously. What is the problem?

[der_fisherman]

Please help me! I build TGS. If you connect the tx coil it beeps continuously. What is the problem?

You must get used to supplying full information, what you have supplied is basically nothing as there are probably several hundred reasons for it not working correctly.....

But to make a start:-

You must take a magnifying glass and check that all solder connections are good, that there are no short circuits between adjacent tracks and components.

Next lift all chips and make sure no legs are bent, make sure that the chips are correctly orientated (change that chip if wrongly orientated as it may be now damaged).

Check against the data sheet for any transistors that may be either with different pinning than originally planned for, that happens between manufacturers.....

Make sure that the CD4024 is the actual CD version for higher voltages, some are only for 5 volts and will get hot and burn out!!

How did you shield your coils?

Did you connect the shields in the coil head?

Wrongly applied/connected shields can cause REAL problems. If you remove the connection to the receive coil only, does the noise stop?

Which version of the TGSL did you build?

regards

Andy

[Farside]

You will get this if there is no -6V.
This is generated from pin 12 of U2 so check that there is 7.3kHz (roughly) signal there.

If there is then check that +8V is present at the Emitter of Q3 and also check Q3 and Q4 are in their correct places and aligned correctly.

If no 7.3kHz is present then check to see if there is 14.6kHz (roughly) on pin 1 of U2.

If yes then check pin 14 of U2 has 8V and pin 7 is grounded.

If no then check to see if there is 14.6kHz on R71. If no then the chances are your coil is short or open. Check the resistance of your coil. Otherwise check the alignment of Q1.

[Ropcsika]

+8v i measured 7,95 volt
-6v i measuired 6,18 volt

U2 pin12 7,66 Khz
u2 pion1 15.32 Khz
pin 7 and 14 7.94 volt

ic is not cd4024 only hcf4024

coil frequency is too high. around 17Khz

Which is the q1 and q3, q4- 2n2222 and 2n2907?

[Ropcsika]

only the tx coils connected. I want to nulling the coil. coils without no sound. okay. I check everything.
How can i make and where connect the shield? Starts and end point

[der_fisherman]

only the tx coils connected. I want to nulling the coil. coils without no sound. okay. I check everything.
How can i make and where connect the shield? Starts and end point

There are many ways to null, probably TGSL 101 parts 1 & 2 from Don B. is the best document on this website, find it and download it and read it. It will become your TGSL Bible.
Basically connect the Tx coil only and put a scope on the Rx coil and adjust the overlap for the minimum voltage. Some people use a meter instead on AC and they also get good results I am told.
regards
Andy

[Dennis the Mennis]

http://www.geotech1.com/forums/showp...56&postcount=1

for example TGSL 101 part1

DTM