choice for a 18 khz

[Tim]

Hmmm. If you were using the original circuit with a coil tuned to 18kHz you would simply change the coil. However, if you were trying to make a 6.6kHz coil run at 18 kHz by switching the TX cap/peripheral component values, and Rx peripherals you would only need a on-off-on 6 pole switch. But I am sure there may be other internal adjustment settings that would make this impossible with a VLF..Very easy with a BFO, but not so with TX/RX..(?)

[lamoiz]

..or replace a 2-position 4RT switch ....

[lamoiz]

hello, I need a switch 8 RT ..8 changeover contacts. I will want to know if there is an integrated circuit that can do that .. if yes which ..?I wanted to switch from 6.6 to 18 khz directly .

[Tim]

For gold prospecting the black sand meter of the GMT/GBpro/Makro Gold Racer is an invaluable tool and should be considered for all LF builds.

[dbanner]

Gm3 50khz very good machine. Fisher gold bug 2 even better.

[kt315]

[kt315]

what is your interest in 18KHZ ?

more productive way is to buy faulty GMT3, to give the board to me for desolder.
then i do PCB and everybody gets - PCB, schematic, full part list and good project of 48kHz gold detector.

[6666]

good evening everyone,
After having made four IDX PRO and three SURF PI, I would like to know what 18khz detector I could do?
In your opinion, what machine 18khz is feasible at home? in analogy of course ....
thank you

what is your interest in 18KHZ ?

[lamoiz]

Well, how boring, but again thanks again to to all guys who advising to read this book.
But maybe it is to hard to explain some basic knowledges for people, who loves the practise and pick up some experiences from experiented peoples.
I think, that I am not too bad to create a pcb and make a working unit. But anyway I need a schematic, I'm a mechanic and not an electronic engineer.
Some basic skills in electronic I got and I realy like to learn and search the informations here in this forum, but I'm not interest, for understanding the task of any, every little grain of sand in the desert.

the holy reading of the specialists. A superb book. does volume 2 exist?
Blobber one more time, I agree with you ..
tomorrow I test in real condition the new dd 28 has 18khz .the result tomorrow evening ..

[CDI]

Thankyou CDI, I know that I can trust your words, as I already said before. I respect your knowledge in practise and I am thankful for every help in the past you gave.
But anyway, I realy like to see videos.

I will make tomorow, i'ts too late now to record and upload, from my clock now is 12:17.

[blobber]

That's exactly right capacitors in my coil head, as i said, 220 and 6.8n
This is done on factory Whites Classic ID with vdi meter which is the same platform as a little bit newer IDX.
In my case, this coil working also on my 3 homemade idx machines and giving very similiar result.
My 28 cm coil is tuned to 12 khz, i repeated many times here setup for that.
330n for TX and 8 - 10n for rx. I have 1 channel scope, so i'm not able to measure phase shift, but i'm going to get minimum ac voltage just like when we nulling with multimeter.
For "not bealivers" i can make video with both coil's.
They are both quiet in the real field, both are very deep in real soil, they have both perfect discrimination and geb.
I'm not so familiar with theory and web calculation for frequency setup, i like experiments and real practice... try everything and fix coil where is working perfect, just that.
Regards

Thankyou CDI, I know that I can trust your words, as I already said before. I respect your knowledge in practise and I am thankful for every help in the past you gave.
But anyway, I realy like to see videos.

[blobber]

Well, how boring, but again thanks again to to all guys who advising to read this book.
But maybe it is to hard to explain some basic knowledges for people, who loves the practise and pick up some experiences from experiented peoples.
I think, that I am not too bad to create a pcb and make a working unit. But anyway I need a schematic, I'm a mechanic and not an electronic engineer.
Some basic skills in electronic I got and I realy like to learn and search the informations here in this forum, but I'm not interest, for understanding the task of any, every little grain of sand in the desert.

[lamoiz]

It might seem obvious that you should tune the TX and RX coils to the same frequency to maximize sensitivity, just like tuning a receiver to receive a radio program. However, in practice this can cause a lot of instability problems when used in the field. Also, there needs to be a certain amount of RX phase shift (relative to the TX) to make the GB and DISC circuits work correctly. Therefore metal detector manufacturers set the RX circuit off-resonance to improve stabilty and reduce drift, and improve manufacturability. The amount by which the receiver needs to de-tuned from the TX depends on the actual circuit you're using, and is best found by experiment. This may require you to tune the receiver either above or below the TX frequency. There are no hard and fast rules for determining the best settings, nor is there some secret recipe for success.

thank you qiaozhi. finally a real and good clear explanation ..

[CDI]

I am a bit confused, because I have different schematics and layout files too on my computer, but wich are the last actual files for IDX?
Just for compare with my buildd one.

That's exactly right capacitors in my coil head, as i said, 220 and 6.8n
This is done on factory Whites Classic ID with vdi meter which is the same platform as a little bit newer IDX.
In my case, this coil working also on my 3 homemade idx machines and giving very similiar result.
My 28 cm coil is tuned to 12 khz, i repeated many times here setup for that.
330n for TX and 8 - 10n for rx. I have 1 channel scope, so i'm not able to measure phase shift, but i'm going to get minimum ac voltage just like when we nulling with multimeter.
For "not bealivers" i can make video with both coil's.
They are both quiet in the real field, both are very deep in real soil, they have both perfect discrimination and geb.
I'm not so familiar with theory and web calculation for frequency setup, i like experiments and real practice... try everything and fix coil where is working perfect, just that.
Regards

[waltr]