On Sat, Sep 24, 2022 at 01:16 PM, Brooke Clarke wrote:
Self capacity is a very important factor.? Hence the experiments related to TPI.? But for me it's hard to make sense of TPI.? So mentioning the physical wire diameter, or the equivalent the maximum TPI for a close would coil, would help.
?The wire I used 660/46 litz wire, it is 0.065" in diameter, meaning 8 TPI with be very close to 1 wire spacing. Close wire spacing is just over 15 TPI.
EBAY Litz supplier, https://tinyurl.com/mr2aw5zm
The old books I referenced when winding AM broadcast coils talked about a spacing of one wire diameter.? This is easy to do using a loop of wire with a weight.? Note any dielectric material near the coil adds capacity, and for some insulators even adds resistive loss.
Styrene is high on the list of low loss materials. I would have liked to made the walls of the coupler much thinner, but I had someone volunteering the work, 5 coils, 5 different threads, so I didn't ask him to remove a lot of material. I also made the the thread cut just the minimum, so the wire wasn't surrounded by styrene.
Getting the minimum wire length for a given single layer cylindrical coil inductance, like the ones shown in recent posts, depends on the form factor.? AFAICR making the diameter about 2.5 times the length is near optimum.? That's to say for a 6" diameter form the coil length should be about 2.4" long.?
The 2.5 ratio was not what my experiment came up with, My test showed 1.97. The Litz man's page shows a test of a 1.9 ratio coil with a peak Q of 1472 (805kHz), but he adds, 2.46 is the best ratio. I don't know if that would hold up over all diameter coils.
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