IDX-PRO+VDI

[hoadlies]

Hi Barry, I would use the red black for Tx -- also Id say solder the drain wire of the cable as the foil is all and of course does not take solder.

If you send a pm with your email in I will send you an interactive schematic with scope traces on the test points S

OK THANKS STEVE PM-SENT..
CHEERS BARRY..

[hoadlies]

HI TO STEVE & ALL ,,
Well Steve I finally got my old brain around the single Channel Scope ,Instuctions you gave Earlier in the thread ,, What with our BL*&%#y Heat wave I have not had much time in my W/shop..
BUT today I think I worked-out your proposed method THANKS-MATE..

I procured a small tin of resin & catalist today & some more MKT cap values to play around with [Tuning-coils]..
GETTING THERE SLOWLY ..
CHEERS From ''Down-under'' ,,,,,,,,,,,,,BARRY..

[golfnut]

no worries.
from memory,
you will need 2 scope probes/leads..
plug one on the EXT trig… and hook end onto Tx coil - select ext trig - (trigger the timebase/sweep from the tx signal) your scope trace should appear only with your detector ON. If you turn the detector OFF the trace on screen should stop/disappear. This confirms you are using external trigger for trace.
In this State but with det ON – attache your CH1 probe to Tx signal – now you see Tx signal – ( it is also trigerring your sweep )you should be able to rotate the timebase clockwise to see one clean sine on screen. All should be locked and stable – make a note of where the sine is on screen. Trace it with chinagraph pencil or tracing paper?
Move CH1 from tx signal to preamp output and crank the volts/div clockwise to see leaked Tx signal from preamp – it should be inverse of what you saw for tX sig and 300mV or so. (or another way,, about 180degrees out of phase )

This condition should be true when screened nulled and potted ideally with unit in box.
If true you should be able to reject ferrite with geb, and reject iron with disc and your good.
steve

[hoadlies]

HI STEVE & ALL ,,
I have finally worked out the method You kindly suplied[Exturnal trigger]& yes I get a very good signal [Nice clean trace ]on TX ,But pin 6 [preamp-out] is not really good ,much weaker it seems & cannot get 180deg offset ???? ..
My TX freq is OK @ 6.5 khz with a MKT- 1 uf ,My RX is 4.99khz ..is this too high ????? I have 32nf there ????[This I set with the method that S/D supplied ,using my SIG-GEN & FREQ counter getting best level on scope trace..
BY GEE ,you do not have to move the coils very far to upset the RX trace It flat-tops& bottoms- easilly ..

I appreciate the help mate ,,,,,,,,BARRY from a hot Australia ..

The trace is not as nice as your picture you sent me ..

[der_fisherman]

no worries.
from memory,
you will need 2 scope probes/leads..
plug one on the EXT trig… and hook end onto Tx coil - select ext trig - (trigger the timebase/sweep from the tx signal) your scope trace should appear only with your detector ON. If you turn the detector OFF the trace on screen should stop/disappear. This confirms you are using external trigger for trace.
In this State but with det ON – attache your CH1 probe to Tx signal – now you see Tx signal – ( it is also trigerring your sweep )you should be able to rotate the timebase clockwise to see one clean sine on screen. All should be locked and stable – make a note of where the sine is on screen. Trace it with chinagraph pencil or tracing paper?
Move CH1 from tx signal to preamp output and crank the volts/div clockwise to see leaked Tx signal from preamp – it should be inverse of what you saw for tX sig and 300mV or so. (or another way,, about 180degrees out of phase )

This condition should be true when screened nulled and potted ideally with unit in box.
If true you should be able to reject ferrite with geb, and reject iron with disc and your good.
steve

Golfnut, you are a clever user of a single scan scope.....Well explained as well. Brilliant.
I have been lucky and always had twin channels, but if ever one goes down, I will still be able to use the scope!!!!
Thanks again and have a great day.
Andy

[golfnut]

Hi Barry, your right the null is very fine and Notchy - clever isn't it. The notch is about 65dB approx.

The preamp out is small and is more noisey looking.


If your phase is not 180 deg wrt Tx I should expect some of the following...

1) Cant Fully reject Ferrite
2) Cant fully reject clean small iron
3) Get a double bleep from a single pass of clean small iron
4) Get a double bleep from wanted alloys

S

[paku]

what is caps on idx board is 1u can i put cap code 102

[hoadlies]

THANKYOU to ALL who have helped me get a handle on this project ..

HI TO STEVE,DON, EDU,S/D & ALL ,I THANKYOU ALL for the help & advice given me..[MY 1st build ever on a M/D] to get this IDX-EDU project going..

IT is not yet finished but now in testing Phase using h/Built DD coil & its showing promiss ..

I ALSO found that ''Reading & re-Reading'' the posts here multiple times & printing-out the various pages has helped greatly

I must say the friendly advise from this site has been GREAT ..

CHEERS TO ALL From A HOT-AUSTRALIA,,,,,BARRY..

[golfnut]

what is caps on idx board is 1u can i put cap code 102



1u would have case code 105

[hoadlies]

HI STEVE & ALL ,,A Question please...

I have now put my coils into a housing of sorts !!! BUT prior to wiring the coil I would like the Pro's & con's of putting the Caps [ie] Tx & RX , into the coil housing Or could I put then into the control box as I ''think steve did but not shure '' To allow any further alteration of values etc etc..

My kit is coming along slowly & it WORKS !! My nulling is a bit touchy ,, But I cannot achieve 180deg offset ??? <but it seems to be Ok as air test & can Geb-out ferrite [Just] ..
I ended-up Shielding with a mixture of graphite & PVA ,, I tried many other mixtures but none worked very good ..
What I did was taped the coils first with insulating tape then masking-tape then wraped plain copper wire around spaced about 1'' apart then applied the graphite glue mixture & then another wrap of insulating tape ,[leaving of course a gap] .its well under the conductivity to what the aluminium tape was which seemed to make funny noises ..[''we'll see I guess when actual tsting on ground ..]

ALL THE BEST FROM AUSTRALIA,,,,,,,,,,,,,BARRY..

[seadoggy]

u can't put cap 102(that is 1 NF or 0.001uF).regards

[dfbowers]

HI STEVE & ALL ,,A Question please...

I have now put my coils into a housing of sorts !!! BUT prior to wiring the coil I would like the Pro's & con's of putting the Caps [ie] Tx & RX , into the coil housing Or could I put then into the control box as I ''think steve did but not shure '' To allow any further alteration of values etc etc..

My kit is coming along slowly & it WORKS !! My nulling is a bit touchy ,, But I cannot achieve 180deg offset ??? <but it seems to be Ok as air test & can Geb-out ferrite [Just] ..
I ended-up Shielding with a mixture of graphite & PVA ,, I tried many other mixtures but none worked very good ..
What I did was taped the coils first with insulating tape then masking-tape then wraped plain copper wire around spaced about 1'' apart then applied the graphite glue mixture & then another wrap of insulating tape ,[leaving of course a gap] .its well under the conductivity to what the aluminium tape was which seemed to make funny noises ..[''we'll see I guess when actual tsting on ground ..]

ALL THE BEST FROM AUSTRALIA,,,,,,,,,,,,,BARRY..

Hey Barry.. Glad to hear that your project is progressing! You may want to increase your cap values in your Rx coil a bit if your GB trimmer is not centered. I have found that ferrite is close for initial tuning but real world may require that you have full range either way. Not sure what the Aussie soil is like!!! Getting phasing correct is a bit trickey!
http://www.youtube.com/watch?v=bVbGzCiRK9w

[golfnut]

Ok Barry, a load of questions....


What sort of phase do you have? (You may sacrifce some null for better phasing. / geb to ferrite)

Ive seen 5 successful idx builds with DDs and they all phase from 160 to 200 degrees

I think Aussie soil is old and has iron and minerals - So I imagine, as Don suggests if your phasing is JUST getting rid of ferrite at one end, then if your the Wrong side, you wont have anything left to adjust geb on your local soil.


What sort of air test on a mid size coin?
If you think it is not good enough, Try a cap change as Don suggests, this may give more sens and this not only walks the Rx tank up or down it adjusts the phase too. So you may peak out the sens and get full geb range.


Do you get single beep on Iron?

Can you reject it with Disc?

Do you get gold/bronze/lead/silver?

S

[Koala]

I ran out of ground balance with both factory and homemade coil. Could not find anything wrong with my board or coil so ended up increasing the value of the ground balance pot by adding a resistor in series

[golfnut]

Barry you asked about the caps in or out of the coil.. I have done both, my homemade coils I put Tx cap in head.
It is popular for Tx to have cap in head on these. Rx tank cap in box.


(I use a Nel Hunter currently and it has NO caps. So Tx cap and Rx cap are in box. The version of hunter I got was for tejon )