choice for a 18 khz

[lamoiz]

I haven't been following this thread. What was the question?

good evening qiaozhy
the question was "what 18khz machine to make at home .."
I had the answer ... read the book of george ... yes it is already read..but often no other track to follow ...
that's why I thank blobber and cdi they were able to answer simply but with certainty to my question ... with an idx pro 18khz. because the IDX is a great machine ... and because there are some great guys on this forum.

[blobber]

Thanks for your well choiced words lamoiz.

[blobber]

CDI would you please share your files and changes for your 16kHz-IDX-beast?

[Qiaozhi]

good evening qiaozhy
the question was "what 18khz machine to make at home .."
I had the answer ... read the book of george ... yes it is already read..but often no other track to follow ...
that's why I thank blobber and cdi they were able to answer simply but with certainty to my question ... with an idx pro 18khz. because the IDX is a great machine ... and because there are some great guys on this forum.

I haven't built the IDX, but it's supposed to be a good detector.
You can get PCBs from SilverDog here -> http://www.silverdog.co.uk/shop2/ind...tegory&path=35

[CDI]

CDI would you please share your files and changes for your 16kHz-IDX-beast?

Ofcourse Blobber. It is well known Mr. Bill mod, i just put trimmer 100R for amplitude. The same coil parameters as described here many times.
TX - 0.58 mH wire diameter 0.42
RX - in my case is 38 mH, wire diameter 0.25 for 38 cm coil, for my 28 cm coil i used 0.17 wire.
I cant remember resistance, but it is not so much important here.
Pay attention on U4 and U3, also, for R25 i put 10K trimmer. This will give u more gain.
Regards

[CDI]

And i forgot capacitor tank...
In previous parameters for TX is 220N, for RX is 6.8N

[Tim]

Great stuff here. I just re-visited this thread. I have an original IDX with Mr Bill mods, but it only came with a 6x4 shooter coil. Blobber/CDI/lamoiz please compile parameters and mods in one post?? I am sure others would like to make an 18kHz coil for their IDX's. What a versatile machine it would make it.
Lamoiz(?) said about a 50kHzcoil for this.. I wonder? But perhaps this frequency will be too much for the IDX, as the TX/RX inductance relationship on the GB/pro & GM/GMT are both about 10:1.

[blobber]

And i forgot capacitor tank...
In previous parameters for TX is 220N, for RX is 6.8N

Thankyou CDI for your informations, I will try this mods. I still use a DD in original setup and one concentric in 10kHz.
But are you sure about coil/cap values. I made a calculation with your parameters and I get this:
TX 0.58/220nF/14.09kHz
RX 38mH/6.8nF/9.90kHz
The difference is more than aspected, otherwise when this setup is good working for you, maybe this higher gap is the secret for your success.

Maybe one expert could explain about it?
But an explanation with helpfull words please!

[lamoiz]

Maybe one expert could explain about it?
But an explanation with helpfull words please!
totally agree with you blobber! an explanation with useful words.

[Qiaozhi]

Thankyou CDI for your informations, I will try this mods. I still use a DD in original setup and one concentric in 10kHz.
But are you sure about coil/cap values. I made a calculation with your parameters and I get this:
TX 0.58/220nF/14.09kHz
RX 38mH/6.8nF/9.90kHz
The difference is more than aspected, otherwise when this setup is good working for you, maybe this higher gap is the secret for your success.

Maybe one expert could explain about it?
But an explanation with helpfull words please!

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.

[blobber]

Thankyou Qiaozhi, that answer was what we need.

[blobber]

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.

[kt315]

Maybe one expert could explain about it?
But an explanation with helpfull words please!
totally agree with you blobber! an explanation with useful words.

good book to read first the time to reminder guys.

[dbanner]

[waltr]