Ok, Here's the story. I built a Surf Master PI from kit. I had a original Surf Master Coil I planed on using. It Sucked. I built a simple Mono Coil and it doubled the detection on all targets.
This detector would be more then fine hunting beaches or ToT lots if you don't mind the Dig It All thing. NO Were like a Gold Machine. I Gifted it to a kid.
Next I built a Mini Pulse Plus. This This detector can handle being set to run down at or below 10uS of delay. This has potential of a half Azz nugget machine. I needed a Faster Coil to allow it to do so. Faster meaning from Tx Pulse to Sample time. The amount of time it takes the Coil to cancel the Fly Back voltage , less time.
I don't want to get into all aspects of that here. I just want to know if some of you are interested in playing at making your own simple PI Coils.
I'm not trying to produce a Mine Lab Machine here just a super simple PI that DOSE Have the potential to find relatively small Gold. CHEAP, Did I tell You I'm Cheap Skate ?
I have the GMT as my primary Gold Machine. I just want to play with the PI thing too.
At first I started Playing with Super Simple Mono coils. Some came out sorry. Some not so bad. Some Quite dang Good.
Next to speed up the Coils I learned about the Basket coils. Thought I had it going until my third failure. Still working on some but I just can't seem to Produce that good of a coil.
I got messing around with my High Dollar coil forms and came up with something I've never seen anyone do. A Stacked Basket coil.
The Idea behind a Basket Coil is to lower the Coils inherent Self Capacitance that Boost the Fly Back Voltage and causes the coil to take longer to settle down after the Tx Pulse ends. The Basket Coil dose this by putting more distance / space between the winding's of the coil lowering Capacitance. Previous Basket coils use a radiated spiral wind. Starting from the Inside progressing outwards. This works most well in lowering the capacitance but it also lowers the Inductance some what. A coil with Higher Inductance is better at detection of the Target signal but also contributes to the Fly Back Voltage. This Stacked Basket Coil does the same thing in lowering the Capacitance in the same fashion. Keeping the Winding's separated . It seems to have a advantage over the Spiral Wind Basket in that the winding's produce a more consecrated target signal because of the formation of the coil shape. The spiral type basket the winding's progress outwards and this tends to reduce the concentration of the Target signal. Unlike the Spiral the Stacked keeps all winding's perpendicular to the in respect to the target signal. More Winding's exposed to the signal gaining the ability to gather more of same. The coil sees the target signal some what like a Mono would but without the Added Capacitance that keeps the Mono Coil from running Fast.
This Geometry of coil has another beneficial quality. The Generated Field is concentrated in the vertical plain. Whats to say it detects more below and above the coils then a Mono can. DEEPER ! As more target signal of the same strength is exposed to more winding's at the same vertical plane I don't see how this could not translate to more target signal. I have a New Oscilloscope that I need to test this with. My old DIY Kit DSO 138 Scope was not up to the task.
Rant Over LOL
My current Resources:
Free Wire. I salvage all my wire from Old TV sets. The Degassing Coil being the primary source. All Older TV with a Picture Tube has them . More Usable wire can be had from the Yoke Coils at the End of the Tube. One Degassing Coil provides enough wire to build at least three or four coils or more. Some of the Newer TV's they used Aluminum Wire for the Degassing Coils. It works fine too if you want to use the stuff. I've made some decent Coils with it. You just have to use Mechanical Spices sense you can't solder the stuff. Not a Issue.
Wire Forms. I started building my own and found it a royal pain. Had to create a New Form for every Coil type I wanted. Wicked Wanda the Wonder Wife solved that for me. Out of the Blue she say, Eaaaaa! What wrong with these ?
She Relinquished her set to the cause.
I have a 5" 7" 9" and 11" loom.
You can do Mono Coils, DD Coils and Yep, Stacked Baskets.
Test Equipment: I have quite a gathering of decent equipment at hand. As for coils I rely on one of the most low cost items at hand. A $7.00 Test About All O Matic !
These things are Dirt Cheap. Did I tell ya I'm a Cheap Skate ?
This thing will tell you any and all you need about a coil .
It can tell you the Inductance and resistance in a single test.
Coil Shell Housings.
There are a few people that produce them around. My Favorite Mr Hays shut shop.
A guy named DB Bowers makes some good ones for a reasonable price.
For the most parts I improvise. Use Coil Skid Shell as housings, Old Coils dissected. Bucket end the lot. Only limited by your imagination on that one.
Shielding. I use the good ol Copper tape on all Mono Coils. Cheap and it works fine. Did I mention I'm a Cheap Skate ?
I use Graphite spray on all others. You can not wrap the Stacked or basket coils.
Here are a few crappy photo's of my mess and some basic information to ponder.
I have everything needed to produce a DIY coil for my GMT that I'll tackle some time this winter I think.