TESORO GOLDEN SABRE

[simonbaker]

spikes

Hi,
they are always there... amplitude can change but you cannot totally eliminate: it's a drawback of design.

Kind regards,
Max

Interesting video - spikes reminded me of TGSL V+, V- busses. Ferrite anyone? (not to be confused with vegemite...)


-SB

[Dr Vel]

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

Not if no charges exist to be affected by the magnetic field. What you are relating to in terms of a moving EM wave misses the point that the alternating magnetic field would not exist unless there were its counterpart the E field. Your alternating magnetic field alone in space is doing nothing if there is no conductor within the field. A conductor is only a conductor because it contains discrete charges, which if affected by the field produces an EMF due to the movement of charges within the conductor. If you stuck your hand in a 10 Tesla 60 HZ magnetic field you would notice nothing. Unless you were wearing metal. Insert a coil in that field and I would not advise holding the leads. Probably I am explaining this poorly but in effect your alternating magnetic field is not going to produce radio waves of any noticeable amount in free space. However a wire in the field would then contain alternating charges which could radiate transverse EM. A coin in the ground in that purely magnetic field will radiate a counter field back at you, as well it would be producing an actual EM wave yet the length of the conductor is so small in terms of wavelength (at say 15 KHZ) the strength of the EM would be very small. Likely too small to notice in your search coil above ground. However the counter magnetic field will move charges in your search coil producing voltages strong enough for your MD to be affected by it.

What I am trying to say is your MD may see the coin but I doubt a transistor radio would even if it covered the 15 KHZ band. Or something like that.

I should clarify; assuming the radio's ferrite loopstick is not in the search head. If it were then we have a BFO type detector?

[simonbaker]

Not if no charges exist to be affected by the magnetic field. What you are relating to in terms of a moving EM wave misses the point that the alternating magnetic field would not exist unless there were its counterpart the E field. Your alternating magnetic field alone in space is doing nothing if there is no conductor within the field. A conductor is only a conductor because it contains discrete charges, which if affected by the field produces an EMF due to the movement of charges within the conductor. If you stuck your hand in a 10 Tesla 60 HZ magnetic field you would notice nothing. Unless you were wearing metal. Insert a coil in that field and I would not advise holding the leads. Probably I am explaining this poorly but in effect your alternating magnetic field is not going to produce radio waves of any noticeable amount in free space. However a wire in the field would then contain alternating charges which could radiate transverse EM. A coin in the ground in that purely magnetic field will radiate a counter field back at you, as well it would be producing an actual EM wave yet the length of the conductor is so small in terms of wavelength (at say 15 KHZ) the strength of the EM would be very small. Likely too small to notice in your search coil above ground. However the counter magnetic field will move charges in your search coil producing voltages strong enough for your MD to be affected by it.

What I am trying to say is your MD may see the coin but I doubt a transistor radio would even if it covered the 15 KHZ band. Or something like that.

I should clarify; assuming the radio's ferrite loopstick is not in the search head. If it were then we have a BFO type detector?

It sounds like your description is relevant to electromagnetic radiation. I still believe that you will find an electric field vector wherever there is a changing magnetic field, regardless if it is near or far field. But I think everyone is trying to say that slowly changing magnetic fields are poorly blocked by conductive shields, which seems true from experience (not having any superconductive shields handy).

Perhaps it is also true that "near-field" changing magnetic fields are not theoretically blocked by conductive containers -- a math (Maxwell) question I'd like to pursue sometime in the next 1000 years. Suitably fast changing electric fields are also not blocked by conductive containers I believe.

-SB

[Farside]

You are correct. That is why conductive containers aren't all that good at shielding mains EMF radiation.

Also correct in the high frequency. I can think of a Faraday cage made of wire mesh. This will clearly not be effective against electro-magnetic radiation in the visible spectrum.

[Ropcsika]

This is my TGSL pcb.


A képet a Képfeltöltés.hu tárolja. http://www.kepfeltoltes.hu


A képet a Képfeltöltés.hu tárolja. http://www.kepfeltoltes.hu

[satdaveuk]

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

Hi
Before you jump in at the deepend the most common fault for the symptoms you have is wrong connections on your 2n2907s and your 2n2222a, check the pinouts because theres at least 3 diffrent type pinouts depending on what manufacture made them.
Far as your hef4024 leave it alone theres nothing wrong with it.

Your boards look ok but always worth doing continuty checks on the traces with your meter before populating.

All the best

[Ropcsika]

Hi
Before you jump in at the deepend the most common fault for the symptoms you have is wrong connections on your 2n2907s and your 2n2222a, check the pinouts because theres at least 3 diffrent type pinouts depending on what manufacture made them.
Far as your hef4024 leave it alone theres nothing wrong with it.

Your boards look ok but always worth doing continuty checks on the traces with your meter before populating.

All the best

Okay, I check everything

[Ropcsika]

YEEEAAAHHHHH....
It's working, soldering defect

[satdaveuk]

YEEEAAAHHHHH....
It's working, soldering defect

Well done

Regards

[Dennis the Mennis]

Mylar shielding question

http://www.geotech1.com/forums/showp...60&postcount=3

http://www.geotech1.com/forums/showp...61&postcount=9



In order to a question by Mullihaka : who has experience with Mylar shielding ?

Are these things we ran into normal or is this due to European manufacturing ?

Please , your comment is appreciated

kind regards ,

Danny

ps I moved the question overhere with the hope this reaches a greater 'audience' .

[Davor]

Have you tried metallic flower wraps? Even if they don't work, they will surely improve your coil's WAF

You may test a piece of such a foil in a microwave oven, and don't forget to put a glass of water beside it. If you get fireworks when you nuke it - it should work.

[freedan3d]

40 cm dd coil for tgsl

Hi Ivconic
I maked tgsl with attach pic version
It sensed a small gold coin under 20cm in air and it was low in my mind
I tried to make a 40cm coil for it but i cant reach 16.5 khz on rx
When i tried to reach 16.5 khz ,its inductance was 4.2 mh and my tgsl componnent was over-heating on 22 ohm resistor in speaker section and it burned
I used 0.25 wire for its.
please help me

Thank you

freedan3d

[porkluvr]

Hi Ivconic

It sensed a small gold coin under 20cm in air and it was low in my mind
I tried to make a 40cm coil for it but i cant reach 16.5 khz on rx
When i tried to reach 16.5 khz ,its inductance was 4.2 mh

freedan3d

The larger the coil you use, the less distance you will achieve on small targets. Smaller coils can give better sensitivity on small targets.

Can you explain what you mean by reaching 16.5kHz with 4.2mH? Was this the colpitts circuit with 22nF and 220nF? If so, I calculate that 4.2mH would get you 17.35kHz, so how did you get 16.5?

A picture is worth 1000 words.

[hazem]

hi
i want to know this part of schematic (disc.switch) in TGSL,i still new with this,and don't know exactly what this,it it kind of pot resistor or switch that when we turn it on MD become all metal,if it kind of resistor what's it value,or if it kind of switch what's that switch that have three terminal!!,plz an explain,i wanna picture for it that show me how to connect it in the circuit(a detailed drawing),and how it's looks outside the case.
thank

[hazem]

hi
i want to know this part of schematic (disc.switch) in TGSL,i still new with this,and don't know exactly what this,it it kind of pot resistor or switch that when we turn it on MD become all metal,if it kind of resistor what's it value,or if it kind of switch what's that switch that have three terminal!!,plz an explain,i wanna picture for it that show me how to connect it in the circuit(a detailed drawing),and how it's looks outside the case.
thank

this's the part i talking about,because i want to know what i say to the seller when i buy it,and how connect it to the circuit (a detailed drawing),plz help