TESORO GOLDEN SABRE

[dfbowers]

I agree that it would not be practical to run at 9V.. Just an observation that I made. It almost seems like the audio struggles a bit, and draws out the audio and makes it sound a little softer. Also, I wonder why I am running 5mA short on the current consumption (that is at steady state.. no signal). I will play around a bit to see if I can get you more details.

I don't have a euro, so I can't compare to some others. I do have a brass arcade token that looks to be similar sized and I can get around 30cm on that in open air. Mine seems to be hotter on low conductors, typical of higher frequency machines.

Don

[simonbaker]

I agree that it would not be practical to run at 9V.. Just an observation that I made. It almost seems like the audio struggles a bit, and draws out the audio and makes it sound a little softer. Also, I wonder why I am running 5mA short on the current consumption (that is at steady state.. no signal). I will play around a bit to see if I can get you more details.

I don't have a euro, so I can't compare to some others. I do have a brass arcade token that looks to be similar sized and I can get around 30cm on that in open air. Mine seems to be hotter on low conductors, typical of higher frequency machines.

Don

I've been meaning to get a Euro also... I'd be interested in results for quarter.

I'm just surprised that the LM7808 works at all at 9v, but clearly it does, although maybe not regulating in normal way.

Your ICs are newer models and may draw less current.

I think its interesting what you found. I would go back and forth with 9v and 12v supplies and try to see what is different in waveforms. Maybe it shifts something into a better configuration that we should know about.

Keep us posted,

-SB

[dfbowers]

Got my hands on a euro.. Forgot my son went to Sweden a few months back. A quarter does not respond like a euro.. The euro responds much better by a few cm. If you can get your hands on a brass arcade token, it's about the same.

Don

[dfbowers]

Simon,

I just had another thought about the euro. If you look at one, it looks like a fat brass ring with stainless or something in the middle. possibly one of the better configurations for a target.. much like a gold ring. If you cut a ring, it goes almost dead as a target since you break the circuit that makes the back EMF. The same thing we do with our shielding. Even though a quarter is larger and possibly of higher conductivity, it's not that perfect "ring" shape. I guess when we are doing distance test on the table we should be comparing "oranges to oranges"??

Just a thought..
Don

[simonbaker]

Simon,

I just had another thought about the euro. If you look at one, it looks like a fat brass ring with stainless or something in the middle. possibly one of the better configurations for a target.. much like a gold ring. If you cut a ring, it goes almost dead as a target since you break the circuit that makes the back EMF. The same thing we do with our shielding. Even though a quarter is larger and possibly of higher conductivity, it's not that perfect "ring" shape. I guess when we are doing distance test on the table we should be comparing "oranges to oranges"??

Just a thought..
Don

I agree. I figure it would be useful to test both so we have oranges and apples benchmarks depending on what you have handy. But the euro is the "gold" standard here, so got to get me one. Also, with quarters, you have to know whether you have an old silver one or a new copper-clad, further confusion. I would like to know what a really good TGSL air-tests with a modern quarter though.

-SB

[dfbowers]

It's kind of tough in the house.. I have 4 computers running, two TVs, dimmer switches, and a few motors on things running.. I would say I get 30cm with a euro and 28cm with a 2008 quarter, with GB set correctly and disc set to just reject aluminum foil.. and that's with the standard 255 mm coil I would be curious to see what others observe as well.

[Dennis the Mennis]

Simon,

I just had another thought about the euro. If you look at one, it looks like a fat brass ring with stainless or something in the middle. possibly one of the better configurations for a target.. much like a gold ring. If you cut a ring, it goes almost dead as a target since you break the circuit that makes the back EMF. The same thing we do with our shielding. Even though a quarter is larger and possibly of higher conductivity, it's not that perfect "ring" shape. I guess when we are doing distance test on the table we should be comparing "oranges to oranges"??

Just a thought..
Don

http://en.wikipedia.org/wiki/Euro_coins


FYI


regards

Dennis the Mennis

[simonbaker]

It's kind of tough in the house.. I have 4 computers running, two TVs, dimmer switches, and a few motors on things running.. I would say I get 30cm with a euro and 28cm with a 2008 quarter, with GB set correctly and disc set to just reject aluminum foil.. and that's with the standard 255 mm coil I would be curious to see what others observe as well.

That is excellent. I think you have the knack for making coils. I hope you keep making some more coils and PCBs and see if you get consistent results to help the rest of us understand what mistakes we're making.

Cheers,

-SB

[dfbowers]

I literally bought over a mile of .25mm wire off of ebay for 50 bucks! That should hold me for a lifetime.. I aim to make more coils!!

[simonbaker]

I literally bought over a mile of .25mm wire off of ebay for 50 bucks! That should hold me for a lifetime.. I aim to make more coils!!

Sounds familiar - I have an 8 lb spool... except I got heavier gauge stuff thinking higher Q would be better, but I think not now, at least for RX coil with standard TGSL circuit -- lower Q actually may be better for various reasons. So at least I can repair vacuum cleaners and starter motors...

-SB

[dfbowers]

TGSL and smaller coils

Well now that It's a little warmer out and I finally got a chance to do a little detecting with the TGSL, I have been comparing the performance of different coil sizes. The advantages of an 18cm coil over a 27cm coil are becoming more apparent. These advantages are not obvious when just doing bench testing:

1. 18cm coil is lighter, and even though a 27cm coil covers more ground,
the fact that you can swing a smaller coil a little faster makes up for it.

2. 18cm coil is easier to pinpoint with, which makes digging faster and can
make you more productive.

3. 18cm coil is less noisy when in actual use.

4. While a 27cm coil can give you more depth, it's advantage is not that
apparent when used in the ground. It "sees" less ground in relation to
targets.

5. 18cm coil is cheaper and easier to make.

6. 18cm coil has better target separation in trashy areas.

7. 18cm coil is easier to use around objects.

8. 18cm coil is much more "sturdy".

Try biuilding one.. you might like it!

[dfbowers]

Bottom view of homebuilt TGSL coils:

[ik5pwr]

good job ,nice work , do you have a pattern of wood model ?

regards Alex

[dfbowers]

Some formers.. I need to start making them out of a plywood as pine tends to warp when heat is applied to one side. Also, they tend to crack easily.

Don

[galaksi]

dfbowers;

technical dimensions, please