IDX-PRO+VDI

[golfnut]

Yes its taking only the signals from the GEB CH, exactly. It will be all metal mode, No Disc action.

Essentially a single channel machine when used like this.



( The Disc Sampling time is preset on these machines, the user merely selects more or less output from the All metal/GEB CH or the Disc CH with Pot 7 )
( The Disc CH Sampler is preset to Disc out most metals you dont want say Iron thru Aluminum )

Other machines actually alter the time position WRT to Tx at which the Disc Channel samples and have a pot in the phase shift Rs and Cs

[calebsone]

I think I see so his mod lowers the disc of the machine making it find all metals easer like a permanent all metal.

[golfnut]

If your looking for small items AND you made this machine as per the general instructions . i.e you made a ~6.5kHz Transmitter - Then, you wont find small objects like small nuggets.

You need to make the Tx work at a higher frequency. You can do this by using a smaller capacitor on the Tx coil and a few less turns on tx coil.

The Rx needs to come up too by the same amount.


For a squeak more sens you can move the Rx coil / cap pair closer to the Tx frequency ~ maybe as much as 80% of Tx freq - to do this you need a trouble free free ground which is uniform in its make up e.g. clean flat soil, or dry sand.

General purpose commercial machines known for finding smaller items cover the range ~17 to 25kHz

Specialist very small gold machines are higher - they are not DEEP - but can find very small items near the surface,

[salih]

golfnut You are correct But I am interested in the small things like gold nuggets, I'm not interested Disc ,I'm interested Stability of the device and good GBE to Find anything small. can you give me Tip and I Predestined

[golfnut]

If you make the fixed R into a trimpot and reduce its value to almost zero - in this state the unit may well air test a little better


What is happening, is the user is feeding more signal from the GEB CH thru the back end of the detector.

As the GEB CH does have higher gain ( due to when it samples ) you would be forgiven for Air test result


What you may not have spotted is, you will be getting LESS Disc action - so it will be harder or impossible to reject Iron or aluminium.


For example if you short out the 4k7 resistor, then wind the P7 Disc pot so the wiper goes to the bottom, in schematic, the back of the Detector is getting all of its signals from the higher gain GEB CH.

The GEB CH is there only to remove ground signals, everything else can come thrrough - because of this you may have had a better air test, to some alloys, but less Disc action (likely none).


If getting Iron is good for you, short out the 4k7 and wind the Disc pot to min. This may give a minor range range improvement to some alloys ( close to Iron phase response ) - but in the ground, in use, it wont be much.

You may lose sens to some alloys like silver which occur later - phase wise or may not see it at all.

Have a try

[salih]

I changed R 4.7K to VR 4.7K to find the best value.

[jlsilicon]

Sorry,
But, I dont see any effect.
Centered / CW / CCW - same range ...

[jlsilicon]

Yes,
What do we change the 4.7K to ???
Oh .. I see, Variable Resistor - 10K Pot in later Schematics ...

[calebsone]

OK is it just something I have to play with to find the right resistance? thank you though because that alone should help.......I hope because its a lot easier than most mods

[salih]

lower

[calebsone]

so what do you change it to a higher resistance lower or take it out.

[salih]

I knew the cause of the problem (( 1-depth sensitivity in the ground is weak compared to the tests the air? ))
Reason for the weakness of the device in the ground is Resistor 4.7k Shown in the picture

[jlsilicon]

Does anybody know the best Mods for increasing the Range noticeably ?

It seems that I had made a few Mods on the original that seems to give me a greater range than my new model without any Mods.

[jlsilicon]

My Project goes beyond the original designs
- and seems to be quite successful !
More info later ...

[jlsilicon]

Thanks for the help from the users.
I got my original working with about 1 foot range.
Enough to work with for the time being.