choice for a 18 khz

[kt315]

if someone at the PDF of the lobo pcb in analog mode ... I am interested ...

decode plz what you wrote.

[lamoiz]

if someone at the PDF of the lobo pcb in analog mode ... I am interested ...

[lamoiz]

so I just finished testing. I built a 28 cm coil. I dropped the highest frequency at 14 kHz and the other is the original frequency at 6.6. I have not managed to do a perfect and identical nulling for each frequency if it is good for 14 kHz then it is not for 6.6 and vice versa. .... For the IDX I think the maximum frequency for the discri and the GB works perfectly, must be between 12 and 14 khz max .. At 18 and 20, the gb and the discri did not walk properly. my dual frequency disc does not work. here I will therefore make a coil adapted to each frequency desired 6.6, 12 or 14 .. Max .. So I return to my first question: what machine to detect @ 18 or 20khz.?

[homefire]

In my some day box I have a few TGSL PCB's from SilverDog. I'm going to see if I can get one to run at 29Khz. Just messing I came up with this so far.

[Tim]

Sorry I just searched for it and couldn't find. Perhaps it is sold already...

[kt315]

Tim
i do not have full data on GM3. only last year i got first pics of the pcb. i have to ask you
follow selling of 'faulty' GM3 housing and help to the forum to find out new project with 48kHz gold nugget detector.
i am not so richman to buy those things from US.

[Tim]

KT I was specifically thinking the GB pot value could be raised to accommodate the appropriate values ?? Or if it needed to be less maybe a switchable R in parallel??
All food for thought.
The reference to Mr Bill mods relates to their being no manual GB adjust without it. Perhaps this is helpful, perhaps not.

[kt315]

However the Mr Bill mods could be followed
---
Bill Crabtree never did 18kHz in IDX. no discucess on this matter.

[Tim]

If the GB does not work, then the machine is useless. However the Mr Bill mods could be followed with component value changes to make the GB work again. This might be done with Disc as well, but I am unsure how. No doubt the disc changes necessary have already been discussed extensively in the IDX VDI addition section.

[Qiaozhi]

Hi Mr. Qiaozhi, Thank you for your reply, I wanted to ask you, you can reduce the inductance of self-built coils, then adjusting the frequency with a capacitor. For example, the IDX DD Coil receiving 35.5 MH, reducing it to 5.85 MH with a 200 nf capacitor, same frequency but saving copper wire and weight.
Is it possible? Thank you.

It's possible, but you'll most likely lose some depth. The idea of using a relatively large RX inductance is to increase the sensitivity.

[dgm]

Hi Mr. Qiaozhi, Thank you for your reply, I wanted to ask you, you can reduce the inductance of self-built coils, then adjusting the frequency with a capacitor. For example, the IDX DD Coil receiving 35.5 MH, reducing it to 5.85 MH with a 200 nf capacitor, same frequency but saving copper wire and weight.
Is it possible? Thank you.

[Qiaozhi]

Hello everyone, reading your comments regarding the questions posed by Mr. Lamoiz, about the experimentation on IDX making it work at about 18 Khz, I can say that the frequency is not so important, I myself have done several tests to check if raising the freqenza I could make the metal IDX more sensitive to small nuggets in gold, I just upset the operation of the machine, the GB no longer worked, something that I could not understand, on a self-built 10-inch concentric coil, not still having a perfect nulling the same could hear a small gold nugget about 5 inches, tuned to both 6.59 khz and 18 khz, but once the nulling was no longer detected. I ask the forum gurus to give an explanation. Thank you

It's probably one of two things that causes the problem, or a combination of both.
1. The coil null is affected by the change in frequency.
2. The GB and DISC circuits need some component changes to operate at the higher frequency.

[lamoiz]

Hello everyone, reading your comments regarding the questions posed by Mr. Lamoiz, about the experimentation on IDX making it work at about 18 Khz, I can say that the frequency is not so important, I myself have done several tests to check if raising the freqenza I could make the metal IDX more sensitive to small nuggets in gold, I just upset the operation of the machine, the GB no longer worked, something that I could not understand, on a self-built 10-inch concentric coil, not still having a perfect nulling the same could hear a small gold nugget about 5 inches, tuned to both 6.59 khz and 18 khz, but once the nulling was no longer detected. I ask the forum gurus to give an explanation. Thank you

I agree with you. Discrimination is less effective and GB no longer works ...... @ 17.6khz

[dgm]

Hello everyone, reading your comments regarding the questions posed by Mr. Lamoiz, about the experimentation on IDX making it work at about 18 Khz, I can say that the frequency is not so important, I myself have done several tests to check if raising the freqenza I could make the metal IDX more sensitive to small nuggets in gold, I just upset the operation of the machine, the GB no longer worked, something that I could not understand, on a self-built 10-inch concentric coil, not still having a perfect nulling the same could hear a small gold nugget about 5 inches, tuned to both 6.59 khz and 18 khz, but once the nulling was no longer detected. I ask the forum gurus to give an explanation. Thank you

[lamoiz]

yes actually it is really difficult to manufacture coils..I even built a winding machine..more convenient to make 300 turns of 0.18mm ... I think I have done almost 50 in 1 year ... I progress .. my best achievement is a concentric of 30cm..6.6khz.For the moment I think the most difficult is the shielding.it's really hard ...