PI help

[green]

To get the 3.27Mhz resonance with the awg28 magnet wire I wound a 20 turn single layer coil, ran out of space, added a 2mm foam spacer, wound a 10 turn single layer on top of the spacer. With random wraps the resonance was 1.2Mhz. The awg24 stranded is 7strands of awg32 tinned copper. The LTspice plot looks about the same as the plotted curve. I'm thinking awg32 doesn't look like much of a target. Would 7 strands of awg32 magnet wire in parallel or 7x32 copper not tinned make a difference? Spice Plot included.
I have a lot of the awg28 and was hoping to use it for coils. Looks like it might work for delay times greater than 5 usec.

[Waikiki_Sweep]

My best results I have with Teflon insulated stranded wires (19 strands). Also I make coils "semi-flat". It looks like flat spiral coil but more compact.
For example: 9 layers with two turns each. This trick helps to insulate hot and cold ends of coil and reducing capacitance almost like a flat spiral coil
but also helps to keep surface area smaller to not rise coil to shield capacitance.
Teflon (2.1) or polyethylene (2.25) has lower Relative permittivity and insulated wires help to keep inter wire capacitance low instead of magnet wire lacquer insulation.
Sure stranded wires are better than single acting as target. Probably tinned or just cooper stranded wires may be a little better than silver plated.
Probably it is easy to choose wire comparing how far away you can detect piece of it with metal detector. Less detected is better.

One way is to fight inner capacitance of coil to make it low. But probably we can also to dump coil electronically and make it discharging faster by shorting coil for a short moment before sampling.
You can find interesting solution in MD Chance from: http://fandy.hut2.ru/Chance.htm