This is for @Taggart to help explain winding your own LF coils. I just posted here to consolidate information for reference later. Here’s a link their original thread.
First it’s always a good idea to check the datasheet for the chip if you have it for the input capacitance. Luckily DT hosts the ATA5577C Datasheet for just this reason. If you check out the Electrical Characteristics section you’ll see the available options.
I’m under the impression 330pF is the most common, but if you measured 175pF then let’s go with that. That would mean it’s probably a 130pF chip with a bit of extra capacitance from the leads of your meter. Next you could use this calculator to figure out that you would need a 12.47mH inductor to match this chip.
Even if you suspect the capacitance to be higher, it’s always better to undershoot. Capacitance and Inductance both lower the resonant peak. If it turns out higher than you thought, you can just remove turns from the coil to compensate. If it turns out lower than you thought, you can add a parallel capacitor.
I usually calculate 3D coil dimensions using this calculator from 66pacific, just because I’ve verified it several times and know it works. You can use whatever you want. Calculate a suitable number of turns for the dimensions you have, and start winding. Always good to overwind, because you can easily remove turns. If you’re having trouble reaching such a large 12.47mH inductance in the available space, either use a smaller gauge wire since turns are exponential, or add a strip of thin ferrite around the interior of your winding channel to change the magnetic permeability of the core.
If you really want to investigate the performance more than that, you’re going to need a VNA like pictured above. I’ve posted a video in this thread about how to set one up. It will tell you how far off you are from the target resonant peak. Otherwise, just keep trying until you get the maximum read range.
Here’s an example of an inductance calculation using a 25mm diameter coil with 17 turns that result in it being 4mm long. The resultant inductance is 44.6uH
