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Originally posted by waltr
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An exmple of my concetric coil with GEM how it looks
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My tx 0.25 wire (25ohm) and rx 0.45 wire (12-13ohm),rx coil 1 cm bigger in diameter than tx, for shield i have used GEM(ground enhancement material) maked it likuid and get outside the coil glued,its 200ohm everywhere,but i have not put it in my board circuit yet,i will put tomorrow.This GEM i have used before in my concetric coil and no false signals had in my detector ,very good,i search in silent in every earth condition ,becouse the grafit has about 60kohm ,i ptefer to use GEM which i can arrange its ohm as i like...for me 200ohm is best and hard to get in shield.
An exmple of my concetric coil with GEM how it looks
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Interesting material this GEM. Found info:
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Yes its the material that they make the graphite spray and sell back to you x1000��Originally posted by waltr View PostComment
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hi Ivconic
thank you for all that information you post on geotech
i decided to make TGSL detector(schematic in Don Bowers guide) so first i test the schematic
on bread board by using high quality components but it did not work!
coil information : TX = 6mh(25 ohms) and Rx = about 6.5mh(26 ohms)
i tried to troubleshoot the circuit and found out that TX circuit does not work anyway
why? because transistor colpitts oscillator(tx circuit) won't work without collector load and base bypass capacitor, in this case(this is a common_base amp) so i added a 10k pot between collector of 2N2907 and ground and a 220nF cap between base and +8 supply rail and it worked, no surprise
but i only get 7 Vpp of amplitude for the best which is reasonable for +8V supply but not 16V(i don't know how it is even possible to get 16V out of +8!!!
since it's a oscillator not a voltage doubler)
so my question is: what schematic do you guys use in order to make it work???
i,ve tried many times with "original" and even different designs but it's not working at all.
and my own design is not working as it supposed to in that makers guide(Don Bowers)
i,m completely disappointed whit this project and kinda wrong information
my rx frequency are the same as tx(14.5 KHz) and i can't change it
so please help me if you don't mind, thank you very much
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leave it out. buy a board from russian and do normal project, без косяков. you'll get only trouble with tgsl.
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A bread board may have too much stray C. It should work somewhat.Originally posted by Mr.Jaick View Posthi Ivconic
thank you for all that information you post on geotech
i decided to make TGSL detector(schematic in Don Bowers guide) so first i test the schematic
on bread board by using high quality components but it did not work!
I prototyped the TX oscillator on a PCB prefboard and that worked first time. I use this to test coils looking for the frequency they oscillate at.
Prototype just an oscillator and check each of the RX & TX coil on the same oscillator circuit as Dbowers recommends in his 101.pdf. The RX & TX coils need to oscillate at a difference of about 550Hz.coil information : TX = 6mh(25 ohms) and Rx = about 6.5mh(26 ohms)
The one I built has about 16Vpp output.but i only get 7 Vpp of amplitude for the best which is reasonable for +8V supply but not 16V(i don't know how it is even possible to get 16V out of +8!!!
I used the EDU schematic which is the same as in Don's 101.pdf but simply bought that PCB from SilverDog.so my question is: what schematic do you guys use in order to make it work???
Of course RX measures the same Freq since it simply Receives the TX.my rx frequency are the same as tx(14.5 KHz) and i can't change it
There is a whole sub-forum on the TGSL here:
Lots of post about getting this circuit going.
It is one of the easiest VLF circuits to build but still has many subtle pieces that must be correct.Comment
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walter
Don Bowers' schematic has fatal mistake in TX colpitts oscillator. look on my right sch of Cobra and you will see R3 is NOT 47k -!
(R10)
somebody (iwkonik?) losted the decimal point.Comment
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Probably somebody before "iwkonik" did that, not me.
Truth is that there are 4.7k and 47k on same place at different versions of W. Lahr retraced schematics.
I just checked my archive and i found out that there are several versions of the same schematic, done by somebody else, much before me started to grow interest in those.
However; there is not trouble with TGSL.
So many people did it so far with success.Comment
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W. Lahr did mistakes in every his sketch. i wrote that billion times. you must YOURSELF check every component
desoldering it off the board. just then you will see right schematic.Comment
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thank you kt315
i will check this out but any further information about this?
for coil making and setup...
i need to design the pcb myself since i'm not in RussianComment
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my pcb and schematic for tgsl:
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227 pages,
5 653 replies,
1 039 663 views !!!
And still you are asking for "any info" !???
In same time you trying to make detector on perfboard without proper coil !??
Complaining in advance?
I mean... C'MON!!!
You're just used as "fuel" for usual KT's rants and rubbish that he posted all over the place, polluting each possible topic on this forum.
... pushing you to buy pcb from ebay... as usual.
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thank you for your attention guys , i did't expect to get some answer from expert people any time soonOriginally posted by waltr View PostA bread board may have too much stray C. It should work somewhat.
I prototyped the TX oscillator on a PCB prefboard and that worked first time. I use this to test coils looking for the frequency they oscillate at.
Prototype just an oscillator and check each of the RX & TX coil on the same oscillator circuit as Dbowers recommends in his 101.pdf. The RX & TX coils need to oscillate at a difference of about 550Hz.
i've done this but not working
The one I built has about 16Vpp output.
I used the EDU schematic which is the same as in Don's 101.pdf but simply bought that PCB from SilverDog.
the pcb and schematic are same i've already checked
Of course RX measures the same Freq since it simply Receives the TX.
exactly my knowledge says the same thing but in that guide it says the rx tank should oscillate at about 16.1 khz!
There is a whole sub-forum on the TGSL here:
i've read a lot of information about this particular subject on here but still i'm a fool
Lots of post about getting this circuit going.
It is one of the easiest VLF circuits to build but still has many subtle pieces that must be correct.Comment
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thank you very much i will check that again i am hopefulOriginally posted by kt315 View Post
btw i used 0.25mm wire for both coils and get 14.57 khz for tx and 13.9khz for rx both in tx circuit(my retarded design
)
so is there any problem with it?Comment
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"...Of course RX measures the same Freq since it simply Receives the TX. exactly my knowledge says the same thing but in that guide it says the rx tank should oscillate at about 16.1 khz!..."
Presuming that you check RX coil by connecting it at TX coil place. Than you'll see the different frequency, of course.
As for "mistake" made by William Lahr; there is no mistake at all.
At various Tesoro designs you'll see the same resistor vary from 4k7 to 47k.
At Bandido is 20k. Etc.
By strange coincidence i am having one TGSL on the bench right now.
I replaced 47k with 4k7 and i don't see any difference in behavior. Works the same.
2e coin detects at same distance in both cases. Disc, GEB, everything works perfectly smooth and same in both cases.
At the same time there is Bandido II uMax on the bench, with 20k on the place. Works just fine.
So?
If you pay too much attention on KT's rubbish; you'll get nowhere, that's for sure.
I saw part of the schematic you posted and i see dramatic changes in TX stage!?
What the heck you did there man?!
(rhetorical question)
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