IB Rx coil at Tx off

[green]

https://www.geotech1.com/forums/atta...4&d=1601817893

#3 pin 6 enables GB. Connecting pins nand gates #5 and #6 going to #3 pin 6 to -V disables GB.

https://www.geotech1.com/forums/atta...5&d=1601820170 I use 5V logic and +-2.5V for analog, -V is same buss. Values would change for different power supply volts.

[green]

When I make another I want to try higher emitter(base)resistors, think I over damp some of my Rx coils. Maybe 3k instead of 1k?

[6666]

Hi Green, thanks for reply, I thought I replied but something must have gone wrong with my reply.
Been studying your cct, you have put a lot of work in to it

[green]

Thinking about making some more figure8 coils(two round Rx coils connected fig8 with oval Tx). Posted a distance vs amplitude chart awhile back(mono coil). Make Rx coils same as chart. Want to compare distance vs amplitude for the fig8 against the mono chart. I get higher inductance for spiral coils than calculated. More data for comparing inductance. Make smaller coils first, maybe change number of turns pending on test results. Thinking stage, any thoughts appreciated.

Wound one of the 300mm Rx spiral coils for the 300mm fig8. Inductance higher than calculated. 133mm Rx measures 3% higher than calculated. 300mm Rx measures 23% higher than calculated. The 24inch Rx measures 37% higher than calculated. Has anyone compared measured vs calculated inductance for a spiral coil or have an idea why my larger coils measure so much higher than calculated?

calculators I use https://www.geotech1.com/forums/show...112#post271112

[6666]

For what its worth, I have not had much luck with most of those online spiral calcs, the only one that has come close is https://crystalradio.net/professorco...piderweb.shtml but still came out a bit high but thats better than low
I have made two coils useing this calc, with 30AWG wire,pvc covering, useing the outside dimension of wire and I had to remove 4 turns from one coil and two turns from the other.

For a 12 inch ID coil (300mm) it says 21 turns .014 (28 gauge) = 317uH, probably measure's a bit higher

[green]

I calculated 313uH measured 384uH. 300mm ID, 21 turns, AWG 28 magnet wire.

[6666]

I applied professercoyle to my 8 inch ID spider coil which basicly is a spiral, using the ID and wire size , turns etc, it came out spot on.
But I guess the spacers reduce the inductance a tad.

[green]

I applied professercoyle to my 8 inch ID spider coil which basicly is a spiral, using the ID and wire size , turns etc, it came out spot on.
But I guess the spacers reduce the inductance a tad.

My approximate 8inch. Flat spiral a little higher inductance than basket. Calculate 300uH with professercoyle.

[green]

Finished winding the 300mm fig8.

[green]

Don't have a piece of #9 shot but did chart some #8 shot with a couple other sizes. https://www.geotech1.com/forums/atta...6&d=1556470610 Couldn't see a piece of #8 shot with the circuit I'm using with a 8in figure Rx coil. Maybe outside with less noise pickup. Decay(.78us TC), sample sooner or use a smaller coil would help.

Purchased 1 gram of 8mesh gold nuggets awhile back and charted their decay using a smaller coil. https://www.geotech1.com/forums/atta...2&d=1547586775 Tried detecting each one with the 8in figure coil that I used for the 15x15mm aluminum foil above. All could be detected at 16mm, some a lot easier than others. Nugget pictures were taken on paper with 1/4in squares(hard to see).

Shot and nugget charts copied from https://www.geotech1.com/forums/show...835#post252835 reply #287 and #293.

Been trying to detect #8 shot with 133mm coil. Can't detect. Cut a 9mm square piece of aluminum foil(about .64us TC same as #9 shot). Easy to detect. ITMD suggests reducing diameter in half reduces signal 8 times. #8 shot is 2.03mm diameter so signal should be more than 64 times less than foil. I'm using a 6us delay. Target with .64us TC looses 2decades of signal every 3us. Maybe a 3us delay could detect #9 shot? Wondering if there is a PI detector that can detect #9 shot.

[Carl-NC]

Wondering if there is a PI detector that can detect #9 shot.

The Minelab SDC2300 won't detect #9, nor will the prototype Impulse Gold. My prototype gold PI pinpointer will pick up #9 @ 1/4" or so but that has a 1/2" coil and samples at 4us. #9 is roughly equivalent to a 0.25 grain nugget.

[green]

Compared #8 lead shot to 1gram 8mesh nuggets(7 total)I purchased awhile back. https://www.geotech1.com/forums/atta...2&d=1547586775
Nuggets look similar in size but signal strength varies a lot. Would be greater difference with longer first delay, less with shorter delay. Can't set delay much less than 4.5us I used for test.

[green]

Compared #8 lead shot to 1gram 8mesh nuggets(7 total)I purchased awhile back. https://www.geotech1.com/forums/atta...2&d=1547586775
Nuggets look similar in size but signal strength varies a lot. Would be greater difference with longer first delay, less with shorter delay. Can't set delay much less than 4.5us I used for test.

Tried a 3.5us delay to compare with 4.5us delay

[6666]

Hi Green, interesting results with real nugs and such a large coil, is it possible to only show target D and E in the coloured graph in the link please ?

[green]

Hi Green, interesting results with real nugs and such a large coil, is it possible to only show target D and E in the coloured graph in the link please ?

Charted nuggets with my TRT tester in previous graph. Log amplifier is a little slow for some of the nuggets. Charted d and e with the detector circuit I've been using with smaller coil(48mm fig8 solenoid wound), subtracting no target recording from target recording. Nuggets in similar location, probably not exact.